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May 6, 2013

The Lowdown on the Low That's Got Us Down

Extensive rains across the region over the weekend caused numerous problems with flooded rivers, creeks, roads, downed trees and landslides. A break in the rain on Sunday evening produced a beautiful rainbow in Madison County  - but the break was brief and more rain moved in until things began to clear out Monday morning.

The rainfall total at Asheville Regional Airport for the event stands at  4.08" ( 0.57" on Saturday, 3.40" on Sunday, and 0.11" Monday morning)  - but there is the possibility that we will see more rain over the next day or two.

As always - a picture can say so much more than words. The image below shows how much rain has fallen between Saturday and Monday afternoon. Areas in red have seen over 6" of rain!

So - what's causing all this mess?

The unsettled weather is being caused by an area of low pressure in the atmosphere that is meandering around the Southeast U.S. as you can see in this video clip: May 6 Water Vapor.mp4 *. The clip shows the movement of the low pressure area over 24 hours - spinning counterclockwise like a pinwheel. What you are looking at in the clip is the movement of the water vapor in the mid-levels of the atmosphere, as captured by NOAA's GOES satellite. The water vapor shows up as the milky white color and the dark areas are dryer air that does not contain much moisture.

And, while our skies cleared Monday providing some much needed relief from the rain, as long as the low is in the region - it has the potential to destabilize things and produce showers and thunderstorms. (Think of it as an unruly neighbor who likes to throw rowdy parties!) The low pressure area is expected to slowly move to the east and finally clear the region later in the week, but until then, we will continue to see the chance for rain and thunderstorms.

  *Video of NOAA's GOES Satellite Water Vapor as shown by the College of DuPage Next Generation Weather Lab

 

May 2, 2013

If April showers bring May flowers . . . then we should be set!

After a wet April, it looks like the large-scale weather pattern will not shift much as we head into this first week of May. This morning brought light showers into the mountains - especially east of Asheville as you can see in the image below of the Black Mountains taken around 8:00 a.m. this morning.

The abundant rainfall has helped to ensure a very green and lush spring, but some areas of Western North Carolina have seen way too much rain recently.

The rainfall total at Asheville Regional Airport of 5.88" for the month is 2.55" above normal for April. But that is nothing compared to the extensive rainfall that has been occurring to the west of Asheville.  The image below shows the departure from normal rainfall across the state for the last 30 days.  Notice that much of Buncombe and Henderson counties have seen more than 2" above normal rain during April as depicted with the turquoise color. (There's a legend to the right of the image.) But - look to the west where the dark blue and purple colors show widespread areas that have seen over 4" above normal rain just in the last 30 days. A weather spotter in Transylvania county reported 14.57" of rain for the month!

Image credit: NOAA's National Weather Service Advanced Hydrologic Prediction Service

And, this weekend promises to bring more rain as a large weather system approaches from the west, producing a cloudy and cool weekend with an increasing chance of rain Saturday that will last into early next week. That system has already begun to influence our weather as is evident in a cool time-lapse movie of the clouds across our region yesterday.

You'll see the entire day unfold as you look south across the French Broad River Valley from a mountain top in Madison County. Looking toward Asheville - you'll see the low clouds and fog early in the day then a dynamic shift in the clouds as the day goes on. Take note of the low clouds moving in one direction and the upper level clouds coming in from the west ahead of that next storm. You can even spot a fire in the valley and a bee bum that makes its mark of the camera lens. (Oh my!) Click on the image below (or here) to start the video.

April 25, 2013

Blossoms and Buds

It seems like it took forever to get spring going this year. The wet and cool conditions we've experienced during the late winter and early spring in Western North Carolina made it feel like winter just refused to leave our region. (Who can blame it? I like it here too.) But - even now - there's a possibility of frost tonight (Thurs 4/25)!

They say that good things come to those who wait  - and it must be true because many locations are enjoying gorgeous blooming trees. This beautiful scene is from Mars Hill where the Kwanzan cherry and Dogwood trees are in full bloom.

 

You'll spot these Kwanzan cherry trees, also known as Japanese flowering trees, all over Asheville and surrounding communities as they're used quite a bit in landscaping.

You can even see the changes taking place across Western North Carolina this spring  - from space!

The image below is from the MODIS (or Moderate Resolution Imaging Spectroradiometer) sensor aboard NASA's Terra satellite as it passed overhead just before 1:00 p.m. in the afternoon on Tuesday of this week.

Image credit: Image: Space Science and Engineering Center, University of Wisconsin-Madison with annotation by Pamela McCown

You can see the vibrant green of the landscape as trees and vegetation are really responding to the plentiful rainfall, increasing sun angle and warmer daytime temperatures that we have enjoyed recently. You can also see that the higher elevations are a bit behind in the greening up process with the ridge lines still showing more brown than green because many of the trees are just beginning to wake from their winter nap.

Also evident, the spruce-fir forests that are isolated to the highest elevations in the Southern Appalachians. These islands of evergreens thrive at elevations over 5,500 ft. where the climate is too harsh for other trees.  The dark-colored trees stand out in the satellite image above in the Black Mountains, along the Blue Ridge Parkway around Richland Balsam and in the Great Smoky Mountains National Park.

Compare the image above to the scene across the region just one month ago. The image below was produced by the same satellite on March 21st. Western North Carolina had just received a quick shot of snow on that first day of spring. Aside from the triangular area of white snow and the spotty cumulus clouds - you can see that much of the region had yet to turn green with the brilliant colors that come from new leaves and growing vegetation.

And, even though it means that we'll be spending more time during our weekends trying to tame the jungle of growing stuff -  I think it's fair to say that most of us are really enjoying this transition into the warmer seasons.

Parting shot - Freeze Warning tonight!

So, finally!  Spring looks like it is here to stay - but not without at least one last parting shot from winter. Last night's cold front brought in some cooler air and temperatures will drop close to freezing tonight (Thurs) prompting the National Weather Service to issue a Freeze Warning for most of our area tonight and Friday morning. If you've got exposed tender vegetation give them a good watering this evening and cover them up to protect them from the cold.

 

April 11, 2013

Anticipation . . . waiting on the trees and the storms

It's amazing how different each year can be as the ever-changing seasons unfold before our eyes.  You may remember that the spring of 2012 was warm . . . very warm with average temperatures last March that were over 9° warmer than normal in Western North Carolina.*  That warm spring resulted in trees, shrubs and flowers that were already greening up in late March and early April of 2012. 

This year has been significantly different with temperatures in March and early April running well below normal. (We didn't see above average temps until this weekend.) And as a result, the tree and shrub growth is well behind where it was this time last year. 

A picture can always say so much more than statistics and figures, so take a look at the comparison below.

The top image was taken this morning and the one on the bottom was taken the first week of April in 2012. You can see that the growth this year is well behind where it was last year.

This difference is not isolated to our region alone. It's the same story across most of the Central and Eastern U.S. as you can see in the graphic below. The areas shaded in brown and yellow show where vegetation across a large part of the country is still relatively inactive compared to where it was on this date (April 11) of last year. Areas in green show increased active growth compared to last year.

Image Credit: NASA Short-term Prediction Research and Transition Center (SPoRT)

Technically speaking, the graphic above shows the annual difference of the Green Vegetation Fraction (GVF) which represents photosynthetically active healthy vegetation - or in simpler terms - it shows the status of plants and whether or not they are leafed out and growing compared to last year.

The product is produced daily using data from the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard the NASA Earth Observing System satellites and, other than providing us with a cool gee-wiz way to see the dynamic nature of our climate, is used in weather forecast models. (Yes - you'd be amazed at the level of detail that goes into creating more accurate weather forecasts!)

Thunderstorms are on the way!

Keep in mind that we are expecting to see our first spring thunderstorm event later today and tonight as the large storm system that has been creeping its way across the U.S. this week moves eastward and brings a cold front through our region overnight.  Scattered storms are developing this afternoon to our southwest and that activity will move into Western North Carolina as we head into this evening and overnight.  Stay weather aware and bookmark this website to keep an eye on the storms.

*State Climate Office of North Carolina April 2012 Newsletter

April 5, 2013

Warming up . . . FINALLY!

No doubt about it  - late winter and early spring in Western North Carolina have been cooler and wetter than we normally expect. But - it looks like the coming weekend should bring some much needed sunshine and a return to near normal temperatures.

Through much of this week, winter seemed to hang on with a chill in the air, even producing rain, sleet, and a few slushy snow showers on Thursday. And, almost as if to give a parting shot - we received a dose of freezing rain in some of the higher elevations that coated everything with a layer of ice as you can see in the image below of the beleaguered Mountain Laurel and Rhododendrons in my yard.

This fir tree had icicles up to 4" long hanging off of its branches. Notice how the entire structure of the branch is encased in ice.

The good news is that the skies have cleared today and the April sun will have a chance to warm things up as we head into the weekend.  You can see the clouds clearing on the Institute's HD webcam here. 

We should enjoy warmer and drier conditions in the short term because the next large storm system is not expected until the middle to late part of next week. That system will likely bring some colder air with it. So, don't forget that there's still plenty of cold air over Northern Canada that can cause frost and freeze into late April and early May. In other words - don't put the winter clothes away just yet!

An additional reminder as we look forward to next week, warmer air also brings the potential for thunderstorms. This next system may bring the risk for thunderstorms as that warmer air clashes with a cold front. We'll know more as we get closer to the event.

Until then - enjoy the warmer conditions this weekend.

 

March 28, 2013

The Snow Hangover

Significant snow fell again over the higher elevations earlier this week (the week before Easter), which honestly, produced too much of a good thing for many folks in the region.  The image below shows a large snow drift that developed a hanging ledge during the 3 day event. The drift is the result of the 14+" of snow that we received at the higher elevations northwest of Mars Hill during the multi-day event.

 

The map below helps to show where the heaviest snowfall occurred this week.  The brightest areas northwest of Mars Hill, and westward along the NC/TN state line to Max Patch and the Great Smoky Mountains National Park indicate where over a foot of snow fell. 

Image Credit: EarthCast4D

If you're interested is seeing what it was like during the storm - click here for a video. (My first attempt at video editing!)

And while it seems unusual to see snow this late in the season (remember spring started officially last week) - Western North Carolina can see some of its biggest snow events in March and even into April.

When you think about significant snow events to impact the Southern Appalachians in March, it's the "Storm of the Century", the blizzard of March 12-14 1993, that really sets the bar. That system produced the state of North Carolina's greatest one-day snowfall record at Mount Mitchell with 36" of snow on March 13, 1993. The Asheville airport recorded 18.2" of snow during the event, from March 12-14, setting a record total for the month of March.

Image credit: NOAA's National Weather Service via State Climate Office of North Carolina

But the blizzard of 1993 isn't the only big snow producer to strike the region in recent history during March.  A coastal low pressure system produced significant widespread snowfall across Western North Carolina on March 20-21 of 2001. Mount Mitchell recorded 29" of snow on March 21, 2001 (the second greatest one-day snowfall record in the state) and snowfall of over 12" was reported in elevations over 3000 ft. with totals of 24"-30" reported in Haywood, Madison, Yancey, and Avery counties. A coop observer in Asheville recorded 4.5" of snow on March 20, 2001.

Image credit: NOAA's National Weather Service via State Climate Office of North Carolina

Even April & May can bring some big snows.  One of the most interesting sights I have ever witnessed occurred on April 10, 2003 when I was caught in a thunder snow event in Asheville. I'll never forget the size of the snow "clumps" that were falling from the sky during that convective snow event. 

The one storm many locals still talk about - the May 7, 1992 snow that produced 57" of snow at Mount Pisgah. We really do live in an amazing place!

 

March 21, 2013

Happy Spring!! Yeah - right!

A small, fast moving and dynamic system brought snowfall to many places in the region Wednesday night. And, of course, it happened on the first day of spring!

The system moved into the region just before sunset on Wednesday and the evening sky was filled with dramatic clouds that were producing lots of snow.  But - the air was so dry early in the evening that most of the snow was evaporating before it made it to the ground. You can see the snow showers falling as a fuzzy veil from the cloud base in the center of the image below. I shot the image from downtown Asheville around 7:00 p.m.

By later in the evening, snow was falling over many areas of Western North Carolina  - and honestly - it was one of the most impressive heavy snowfalls we've seen in the higher elevations with heavy snow falling as big flakes, but the system moved out quickly producing one to four inches across most of the higher elevations and less than an inch in the valley.

The result can be seen in the image below from the MODIS (or Moderate Resolution Imaging Spectroradiometer) sensor aboard NASA's Terra satellite as it passed overhead around noon on Thursday.

The coming weekend will continue to feel more like winter than spring. Another system will impact the area late Friday with the chance for a mixture of rain and frozen precipitation for most of us, with more snow in the higher elevations. Then, yet another larger system will bring more cold and wet weather on Sunday lasting into early next week - with, yep . . . more snow in the mountains.

 

March 14, 2013

Comet Watch and Coats

No doubt about it - March is off to a chilly start. Today's sunny skies are almost enough to fool you into thinking that spring has arrived . . . until you step foot outside and the brisk breeze and cold air reminds you that it's still late winter.

If the clouds cooperate, I encourage you to bundle up and take the opportunity to spot the comet PanSTARRS low on the western horizon after sunset for the next week. (Look here for images and information on where to look from the Astronomy Club of Asheville.) I bundled up and headed out on Tuesday night - and while I was unable to catch a glimpse of the comet, I did enjoy the beautiful evening scene below.

If you've been thinking that it seems unusually chilly  - you're right.  Average temperatures in Asheville so far for the month of March have been cooler than the normals, with every day but three (last Sunday, Monday, and Tuesday) running below normal.  In fact, most of the average temperatures since mid-February have been below normal.

If you think back to last year, this is significantly different than the weather we experienced during the winter and spring of 2012 when temperatures were running well above normal.  In fact, the high temperature one year ago today was 77° and temperatures this time last year were consistently 15° warmer than normal.

So, what's the difference? The large-scale weather pattern in the Northern Hemisphere is much different than it was during late winter last year and we can look to the polar vortex for an explanation.  The polar vortex is a band of winds that blow counterclockwise, circling the Arctic.  Last year, that band of winds was very strong and acted as a dam that kept much of the cold air locked up over the polar regions, and out of the lower 48. (Scroll down to the February 16, 2012 Fun Facts for more info.)

This year, especially for the past 30 days, the vortex has been much weaker and cold air has spilled across the U.S./Canadian border regularly as strong storms crossing the plains have pulled that cold air southward. 

The good news - spring is right around the corner with the vernal equinox signaling the start of spring next week at 7:02 a.m. local time on Wednesday, March 20th. And while it's no guarantee that the winter weather is over, it does mean that those beautiful spring flowers are not too far behind.

 

March 7, 2013

A Real Snow Job

Were you part of the "haves" or the "have not-so-muchers" this week?

As you can see from the image below - the higher elevations of Madison County were definitely part of the haves with about 6" of fluffy snow over the weekend and another 6" of blowing blizzard-like snow Tuesday night & Wednesday.

Once again, the Asheville Regional Airport missed out on measurable snowfall, recording just a trace each day in this week's snow events and leaving most folks in the lower elevations still hankering for a good old-fashioned snowfall. While some of us (ummm - me!) at the higher elevations are REALLY looking forward to spring. 

Again, in Western North Carolina,  it's all about location . . . location . . . location.

Image: Space Science and Engineering Center, University of Wisconsin-Madison with annotation by Pamela McCown

The satellite image above, taken on Monday, shows the snow that accumulated over the weekend and how it was isolated mainly to the higher elevations. The image below, taken around 2:00 p.m. Thursday afternoon, shows that the snow blanketing the region as a result of the most recent storm did cover more area. However, clouds still blocked much of the view -  and most of the snow that fell in the lower elevations had already disappeared.

Image: Space Science and Engineering Center, University of Wisconsin-Madison with annotation by Pamela McCown

Both of the recent snow events were the result of conditions that meteorologists call northwest flow. This occurs when low-level winds and cold air approach the area from the northwest, and that cold air is pushed up the slopes of the mountains that form the ridge line along the North Carolina/Tennessee border.  As the air is forced up the slopes - it cools and forms precipitation that falls in the form of snow on the mountain ridges along the border and in some of the higher elevations.

These conditions occur fairly often during the cold months and help to create micro-climates along the ridge lines that produce dramatically different weather than what is experienced in the lower elevations. It really is hard to overstate the difference in the winter weather that occurs on the mountain tops versus what happens in the valley.

What does it take to get a good amount of snow in Asheville and the lower elevations?  The right kind of storm.

In order to get a significant snow in the valley, we need a large storm system that is timed exactly right with a strong cold front. Often times, we see these conditions develop when a large area of low pressure develops in the Gulf of Mexico during the cold months. Remember the big snow of December 2009, and the "Storm of the Century" in 1993? Those were both the result of low pressure systems that developed in the Gulf and then moved across the Southeast U.S. and up the East Coast. 

While it looks like we're running out of time for a big snowfall this winter - don't count us out just yet. Some of our biggest snowfall events have occurred in March, and even April.

 

February 28, 2013

The Snow Moon  - Could it be right?

Did you know that each full moon has a name? Most of us have heard of the Harvest Moon - the full moon that occurs in October.  In North America, the full moon in February is known as the Snow Moon - or the Storm Moon.*

That could be an important bit of news as we head into the next couple of days.  Remember the saying about March - In like a lion . . . Out like a lamb?

February's full moon occurred on Monday of this week and it made a beautiful entrance over the eastern horizon as you can see in the animation below.

The Snow Moon has been true to its name in the higher elevations where the snow began Wednesday evening producing winter wonderland-type scenes, like the one below from this morning. But, you should know that the large-scale weather pattern over the United States has made a significant shift this week and it looks like we may be in for a dose of winter for the foreseeable future.

This means that we will see colder air in place for the next week or so with temperatures below normal for most of the time period and several storms passing through - each providing the chance for snow.

Asheville and surrounding communities could see snow flurries on and off through Sunday, but it does not look like the lower elevations will see much accumulation over the weekend out if this system.

However, this weekend will bring the chance for significant snow along the North Carolina/Tennessee border where persistent snow showers will result in close to a foot of snow accumulating by Sunday night in the highest elevations.

This weekend's snow will be quickly followed by another storm that has the chance to bring accumulating snow to most locations in Western North Carolina beginning Monday night or Tuesday.

As always, this is an evolving situation so make sure that you stay especially weather aware.

* http://en.wikipedia.org/wiki/Full_moon

 

February 20, 2013

Stunning Sunset

Timing is everything - especially when weather conditions change as quickly as they do in the mountains.  Yesterday morning brought huge fluffy snowflakes to the higher elevations that quickly added up to a couple of inches of snow. And, almost as quickly, the sun emerged and helped to melt most of the snow away. (You can watch the day play out on the Institute's HD webcam here where you can actually see the wet snow flakes hitting the camera lens.*)

The whiplash of a day ended with a stunning sunset that was enhanced by concentric halos around the setting sun. The rings are most likely the result of the light from the setting sun being scattered by tiny smoke, dust, and haze particles in the atmosphere. The scene was so eye-catching that I pulled off of the road during my commute home to catch the image below. In a matter of seconds, it was gone.

In addition to keeping us all on our toes, this active winter weather pattern has brought abundant rainfall to the mountains.  The State Climate Office of North Carolina released a statement today naming January 2013 as the wettest on record for Western North Carolina. You can find that information here.

To date - February has not been a big rainmaker at the Asheville Regional Airport where AVL is reporting rainfall that is 1.28" below normal for the month. However, January was so wet that when you factor last month in, AVL is 3.63" above normal for the year.  Landslides and flooding aside - it's a good thing to have abundant moisture across the region as we head into the spring wildfire season.

And, the beat goes on.  Yet another system will move across the region late tomorrow and Friday adding additional rain into area rain gauges, and possibly more winter precipitation at the higher elevations.

* Note - If you access the Institute's HD webcam on an iPhone or iPad - you will receive an error.  This is an issue that we are aware of and are working to fix the problem.

 

February 15, 2013

Impressive clouds and some COOL news!

It's fair to say that Western North Carolina has been in an active weather pattern this winter.  Every few days, another system approaches the region from the west or northwest, bringing changing weather conditions - and this week is no different. 

Tuesday afternoon saw another one of these systems roll in and as it did, it also brought some amazing clouds that swept over the valley.

These clouds, looking like pouches hanging down from the sky, are called mammatus clouds and show up most often on the underside of thunderstorm anvils (as they did in early August of last year - covered in the August 2 Fun Facts). On Tuesday, these clouds appeared just before the rain moved in and are most likely the result of turbulent air flow within the clouds ahead of the rain.

Yet another system will move across the region late today - bringing much colder air and the chance for both rain and snow, just in time for the weekend!

Yes - that was cool news (so to speak) - but this is even better! I'm excited to be able to tell you about an awesome tool to help you look at the weather that's impacting our region!  The Institute has a High Definition Webcam that looks south across the French Broad River Valley from the north rim of the valley, and you can access that webcam anytime you like here. It's a great way to be able to SEE the weather that's impacting our area - so be sure and bookmark the site.  If it's dark - or cloudy - there's still plenty to see because you can play back beautiful timelapse sequences. It really is a unique way to see what's going on and learn about Western North Carolina's weather and climate - so be sure and check it out! Enjoy!

What are you doing next Thursday afternoon?  The Institute is hosting a screening of the energy documentary film SWITCH at 4:00 p.m. on Thursday, Feb 21st at Ferguson Auditorium on A-B Tech's main campus in partnership with the Colburn Earth Science Museum in Asheville. The screening will be followed by a Q&A session. You'll find more information here. The screening is open to everyone so I hope you will plan to join us  . . . and bring a friend.

 

February 5, 2013

Where did the snow fall?

Western North Carolina can seem like a land divided at times.  The complex terrain of this region has a significant impact on the climate and the type of weather that we experience at any given location.

Case in point, the snow that fell over the region this past weekend. The higher elevations, like the mountains along the North Carolina/Tennessee state line pictured below, experienced significant snow though out the multi-day event while many folks in the valley were left with just a few flurries.

 

The snowfall totals of the mountains seen here were generally close to 6" over the four day period.

The map below shows where the snow fell in our region starting early Thursday morning (Jan 31).

Locations in white generally saw light accumulations  - up to as much as 2". The areas in light blue reported more than 2" of snow. And, you can easily spot the bulls eye of the snow that fell on Mount Mitchell, northeast of Asheville, where 12" of snow was reported. Significant snow was also reported in the mountains of Great Smoky Mountain National Park.

What causes these significant differences over such a relatively short distance? To put it simply - blame the mountains.  Each storm is different, but in general - air is lifted as it comes into contact with the mountains and as the air is forced to rise, it cools, producing precipitation.

Another key factor that determines where the heavy snow falls - wind direction. When the winds are from the northwest, the counties along the NC / TN state line see the highest totals.  A relatively small shift in the wind direction can mean a big shift in where the heavy snow falls.

 

January 29, 2013

Ice - then fire. Be prepared for the Clash of the Titans!

Last week's ice and sleet storm left a mess in several counties across Western North Carolina.  The complex temperature structure in the atmosphere resulted in a thick coating of ice in some areas - but produced just rain in others. The event was a true testament to the complexity of our region and the varied weather that we can experience across relatively short distances.

The image below shows the coating of ice that I found on the railings around my home.  The metal railing and the cables (along with EVERYTHING else) were covered in ice that resulted from the 1/4 - 1/3" of freezing rain that we received on Friday. Meteorologists call ice like this that forms as the result of freezing rain clear ice.

 

But ice comes in different varieties depending on how it forms. If you look closely at the image above, you will notice that in addition to the clear ice that coats the railing, there is also a more feathery-type of ice. This is called rime ice and it is a frequent visitor to the higher elevations of our mountains.

Rime ice forms on objects (trees, antennas, railings, almost anything!) when supercooled water droplets (below 32°F) in a cloud come into contact with an object. The feathery structure of the ice grows into the wind as more droplets are deposited on the object, creating beautiful telltale structures of wind direction. The rime ice in these images formed overnight after the clear ice had developed during the day on Friday.

You can see how the rime ice formed into thin ribbons on the branches of a Japanese Maple.

 

Ice as art!  Below you can see where the wind flow around a stone column created a circular pattern to the deposits of rime ice.

Times change quickly!

Last week's ice seems almost a distant memory as we have been enjoying very warm and spring-like temperatures for the last two days.  But - you know what comes with spring . . . thunderstorms.  And, we'll pay the price tomorrow as a cold front approaches the area, firing thunderstorms as it moves through the warm air in place over much of the Central and Eastern U.S.

We will likely see strong winds and locally heavy rainfall as a result of these thunderstorms tomorrow afternoon. We may see some severe thunderstorms in the region, not a common occurrence in January. The National Weather Service has issued a High Wind Warning for the entire area.  I would recommend that you take a moment tonight when you get home and make sure that everything in your yard is secured so that your lawn furniture and trash cans don't turn into missiles. The winds may also bring down trees.

When is the worst expected - take a look at this animation of the forecast for the day begining at 3:00 A.M. Of note - the dark red color indicating heavy rain and the long wind arrows indicating strong winds from the south and southeast. The wind will switch from the west as the cold front passes - but will still be very strong.

 

 Image Credit: EarthCast4D

I highly recommend this website from the National Weather Service to stay aware of where the storms are. If you look now, you can already see the storms moving through the Central U.S.

 

January 24, 2103

The Challenges of Winter Weather

Winter can bring all kinds of challenges to the mountains. From cold and windy conditions like we've seen today to the threat for wintry weather. And, while snow can bring an almost festive vibe to our area, the threat of freezing rain or sleet is a whole other story.

One of the most important factors in forecasting winter weather is that of precip type (precipitation type).  Precipitation is defined as - water in a liquid, frozen, or freezing form that falls from clouds under the influence of gravity to Earth's surface. When a meteorologist talks about "precip" as opposed to just calling it rain - they are usually talking about more than one specific type - for example - large thunderstorms create more than just rain - they create several forms of precip, including rain and hail.

During winter, the challenge for forecasting weather is often associated with forecasting the precip type that can be expected.  Such is the case with the storm expected to impact our area tomorrow.  While is looks like most areas will experience some precip, the precip type will vary depending on where you are located and you will likely see different types during the event because the temperature profile in the atmosphere will change.

The type of precip that falls is dependent on the temperature of the air that it falls through. Take a look at the graphic below.  On the far right, the precipitation starts as snow, and stays frozen as snow all the way to the ground because the air is below freezing, and stays that way through the entire column of air that the snow passes through.  As you move to the left in the image - you can see that there is a layer of warm air that intrudes into the cold air.  That warm air can melt the snow, turning it into liquid. If the liquid drop passes into air that is below freezing again, it falls as sleet, or freezing rain, depending on how much time it has to re-freeze.

 

The National Weather Service has just issued a Winter Weather Advisory for Asheville and all of Western North Carolina. Much of our region will see freezing rain, sleet or snow beginning tomorrow.

Freezing rain can cause numerous issues, from making travel dangerous, to weighing down power lines and trees. Sleet can cause problems on roads as well.

Be sure and stay alert to changing weather conditions and changing temperatures tomorrow and be safe!

 

January 16, 2013

Winter is about to arrive!

After three days of rain, many locations in Western North Carolina have reported significant rainfall.  Now, the larger-scale weather pattern appears to be shifting into a more winter-like pattern for the Eastern U.S. with a significant winter storm expected tomorrow and arctic air moving in over the weekend. So, hold on - it looks like it's going to be a bumpy ride!

Many of us got a very quick peek of sunshine around lunchtime this afternoon - but that peek, while appreciated, was very short. Meteorologists call that a "sucker hole" because it can lead folks to believe that the wet weather is over.  Don't be suckered in - our weather ride has only just begun!

It's not unusual to see wide variations in the amount of rain that falls over Western North Carolina.  Our complex terrain is partially responsible for this variation and you can see the complexity in the image below that shows rainfall totals over the past three days. Many locations south and east of Asheville received 2" or less of rain, while totals have been significantly higher north and west of Asheville.  You can use the key to the right of the map to see how much rain fell in our area. (Click on the link below the image and zoom into our area to access more information.)

Image Credit: NOAA's National Weather Service Southern Region Headquarters

The rain gauge at my home certainly got its fair share.  I haven't emptied it yet, but this is what 3.5 - 4" of rain looks like! More rain is expected and the threat for flooding continues, especially in those areas that have seen the most rain and along creeks and rivers that are already swollen.

Be aware that the National Weather Service has issued a Winter Storm Warning for our area tomorrow. An area of low pressure is developing to our southeast and will move across our region tomorrow, bringing cold air and heavy wet snow into Western North Carolina during the day. This will likely cause significant issues on area roads tomorrow afternoon and evening - and yes - snow is expected in Asheville and many locations in the French Broad River Valley with the most snow expected in locations north and west of Asheville. As usual - the higher elevations will likely see the heaviest snow with over a foot of snow possible in some places. 

Make sure you stay weather alert and watch for the early closings of schools and businesses tomorrow.  The latest forecast brings the worst of the snow into our area during the late afternoon and early evening making for a treacherous evening rush hour. The heavy wet snow will add to the flood threat and may bring down trees, possibly causing power outages and hazards on the roads.

Be safe and prepare tonight. Much colder arctic air is expected to arrive late Sunday and into early next week.  Hello, winter!

 

January 10, 2013

What will 2013 bring?

Almost every morning this week has started with a blanket of fog across much of the French Broad River Valley, creating what looks like an ocean of clouds when viewed from above.

While the fog can create difficult driving conditions for those of us who are trying to get to work, it is a truly beautiful site when viewed from a different perspective - one that highlights the natural beauty of our region and its diverse landscape.

Weather conditions in our region so far this year have been described as "mild" - with average temperatures at Asheville Regional Airport running slightly above normal for all but three days since the start of the New Year.  And, while it's hard to find too many folks who complain about mild temperatures in January - it does force the question: How will the weather of 2013 compare to that of 2012? You may remember that we had a warm winter and a very warm spring last year.

This week, NOAA's National Climatic Data Center (located here in Asheville) released a preliminary State of the Climate report declaring 2012 to be the warmest on record across the contiguous U.S. (the lower 48 states and the District of Columbia) since records for the nation began in 1895.  The report also lists 2012 as the second most extreme year on record declaring it to be "a historic year for extreme weather that included drought, wildfires, hurricanes and storms; however, tornado activity was below average".

As a whole, North Carolina escaped much of the extreme heat and drought that plagued the Great Plains and Central U.S during 2012 (the drought continues there still). You can see in the table below from NCDC's report that the Spring of 2012 tied for the 6th warmest season on record for the state, while the calendar year of 2012 was also the 6th warmest on record for North Carolina.

Table from: NOAA's NCDC Annual 2012 National Overview Supplemental Material

So, what does the forecast look like for the rest of winter?  The long range forecast is indicating the possibility that some very cold arctic air may move into the Central and Eastern U.S. late next week, but we'll have to see if the forecast models continue that trend. 

If you are interested in learning more about the large-scale climate patterns that help bring wintery weather to NC, take a look at today's Winter 2012-13 Climate Pattern update from the State Climate Office of North Carolina. It's fairly technical, but it does provides a hint about how complex these large-scale patterns are and why long-range weather forecasting can be so difficult

 

December 11, 2012

December is here - in a BIG way!

The month of December had been off to a warm start in Western North Carolina with the average temperature in Asheville for the first ten days of the month reported at 10.2° F above normal.  However, last night's (12/10) cold front has brought an end to the warmth and it is feeling like the holiday season has finally arrived - even bringing some light snow to the higher elevations in Western North Carolina. The image below shows this morning's light dusting of fine snow on a white pine at 4000 ft in Madison County.

In addition to the colder air, the latest weather system also brought some much needed rainfall.  The image below shows the recent rainfall across the region with most of French Broad River Valley receiving less than 1/2 inch. The scale to the right shows the amount of rain indicated by each color, and you'll notice that most of the rain fell in the higher elevations to the west of Asheville.

Image Credit: NOAA's National Weather Service generated using the National Weather Service’s radar and rain gauge data combined. 

Last month was very dry over almost all of North Carolina.  Statewide, it was the 7th driest November on record (since 1895) according to the Climate Summary by the State Climate Office of North Carolina.

December has been dry as well, even with the addition of yesterday's rain, Asheville is over an inch below normal for the month and is 2.75" below normal rainfall for the year, so far.

While it has been dry, much of Western North Carolina has been able to escape the designation of drought, instead being labeled as "abnormally dry" as you can see in the yellow shaded areas in the US Drought Monitor below. However, some of WNC's southern counties have been upgraded to Moderate Drought - shaded in tan.

Image Credit: US Drought Monitor through the NC Drought Management Advisory Council

The good news is that the long term outlook from NOAA's Climate Prediction Center indicates that our chances for precipitation are better than usual for the next 10 days and our local forecast calls for a slight chance for rain over the weekend and early next week providing some opportunities to help us add some additional rain into the rain gauges.

 

December 7, 2012

A Whole New World - On the Dark Side

The dark side may not be as dark as we once thought. New technology is allowing us to see our planet in new ways, especially at night

The image below was released earlier this week at the American Geophysical Union meeting in San Francisco. Produced by the new NASA-NOAA Suomi NPP satellite, the image is a composite of numerous images taken on cloud-free nights that were then merged into one breathtaking look at how we humans are able to light up the night.

Image Credit: NASA Earth Observatory / NOAA NGDC  NASA Earth Observatory image by Jesse Allen and Robert Simmon. Suomi NPP is the result of a partnership between NOAA, NASA, and the Department of Defense. Find this image and others here.

The image of the U.S. above is just one portion of a much larger global view of Earth at night. NOAA reports that it took the Suomi NPP satellite nine days in April 2012 and thirteen days in October 2012 to acquire the data to produce the image. That is 312 orbits and 2.5 terabytes of data to get a clear shot of every parcel of the Earth’s land surface and islands. The nighttime view was made possible by the new satellite’s day-night band of the "VIIRS" sensor (short for Visible Infrared Imaging Radiometer Suite).

Unlike the cameras that we use to create an image in one click, the day-night band of VIIRS produces an image by repeatedly scanning a scene and resolving it as millions of individual pixels. Then, the amount of light in each pixel is reviewed and adjusted so that a very bright pixel does not oversaturate, and the signal from a very dark pixel may be amplified.

The images are so detailed that you can see interesting features about our own region, including the lights of our metropolitan areas, the highway corridors, and even the lights along the coast and Outer Banks.

In addition to creating beautiful images, this new capability to produce visible imagery at night will benefit us all by providing key information to weather forecasters about clouds and fog that is often more challenging to visualize at night using infrared satellite imagery alone.

November 16, 2012

High and dry . . . and cold!

If you think back to your Earth science education, you may remember that one of the ways that meteorologists classify clouds is by their height above the ground.  Cirrus clouds, like those seen in the image below taken this afternoon from the A-B Tech Asheville campus, occur high above the ground, usually at a height of over 20,000 ft.

The word cirrus is Latin for 'curling lock of hair' - and you may have noticed the resemblance today as the skies across Western North Carolina have been filled with these wispy high clouds floating slowly across the backdrop of blue sky.

The cirrus clouds were also visible today from a completely different perspective, as milky-white patches across the region when NASA's Terra satellite made its pass overhead at about 11:30 a.m. this morning.

Image Credit: NASA and the Space Science and Engineering Center (SSEC) at the University of Wisconsin-Madison

Cirrus clouds appear thin and wispy because they form high above the Earth's surface where it is significantly colder than it is in the lower levels of the atmosphere - and as such - they are composed of minute ice crystals instead of water droplets like most clouds that have a more fluffy appearance.

Keep a close watch on the sky over the next couple of days as cirrus clouds can produce some interesting optical phenomena, like sundogs and halos. (You'll find information on sundogs in the October 27, 2011 Fun Facts e-mail, if you scroll down.)

Looks like sunny and dry weather for the upcoming weekend - a beautiful way to head into the holiday season!

If you are looking for a great gift for someone who is weather savvy - I have a suggestion for you. The Atmospheric Sciences Department at UNC Asheville produces an annual weather calendar specific to Western North Carolina. It contains daily and monthly climate data, extremes, as well as sunrise/sunset and moon phases.  It's a great value and a unique gift. You'll find more information here.

 

November 7, 2012

Round 2 for the Northeast U.S. – The Difference Between a Hurricane and a Nor’easter

While millions in the Northeast are still trying to recover from the impacts of Hurricane Sandy, the region is bracing for the impact of yet another storm – the infamous nor’easter.

The image below was taken by NOAA’s GOES 13 satellite at 9:15 a.m. this morning (Wed, Nov 7),  showing the center of low pressure (also called a cyclone) off the Mid-Atlantic coast. NOAA forecasts the storm to continue to strengthen as it moves north today, bringing rain, snow, and/or a mixture of precipitation to areas across the northern Mid-Atlantic and Northeast, as well as wind gusts as high as 60 mph along the coast.*

Image credit: NOAA

A nor’easter** (or northeaster) is an intense extratropical cyclone that tracks along the East Coast of the U.S. These storms are most common in the colder months, from October through April and can be thought of, in some respects, as the cold season’s equivalent to a hurricane. A nor’easter is a large and complex storm that rotates around a center with winds that can reach hurricane strength, creating storm surge, coastal flooding, property damage and large areas of intense precipitation. However, that is where the similarities between a hurricane and a nor’easter end.

While they may look similar when viewed from above by satellites, a hurricane (a tropical cyclone) and a nor’easter (an extratropical cyclone) are driven by different atmospheric conditions.

A hurricane is a warm-core tropical system – meaning it derives its energy from the warm waters of the Earth’s tropical and subtropical oceans. In general, the surface temperature of an ocean must be at 80° F or above to support the development of tropical systems like hurricanes.  Water temperatures this warm are typically found during the warm months in the Earth’s tropical climate regions (within 23.5° latitude of the Equator) and in areas of the subtropics (below 40° latitude) where ocean currents move warm waters toward the poles.  The Gulf Stream is such a current.  It moves warm water out of the Gulf of Mexico, around Florida and up the East Coast of the U.S. The Gulf Stream is one reason why we have hurricanes that make landfall along the East Coast of the U.S. but not the West Coast where the water of the Pacific Ocean is significantly cooler.

A nor’easter is a cold-core extratropical system – meaning that it derives its energy from the interaction of warm and cold air masses.  The image below is generated by a high resolution forecast model valid for the same time as the satellite image above and it shows the temperature differences that are feeding the developing nor’easter. You can see the counterclockwise flow around the center of the storm as indicated by the black wind arrows. The bright colors off the coast indicate warm sea surface temperatures with the oranges showing the warm waters of the Gulf Stream. Notice the blues that extend over the land and into the Chesapeake Bay and Atlantic Ocean closest to shore? Those blues represent the cold air and cold sea surface temperatures in place following the passage of the cold front that helped to power-up Hurricane Sandy into a super storm last week. It is the interaction of these strong temperature differences that is helping to develop the nor’easter.

The impacts of a nor’easter seldom affect those of us in Western North Carolina, but when they do – they make history.  Remember the Blizzard of 1993 when Mount Mitchell recorded 50 inches of snow? Also known as the “Storm of the Century” – that storm was a nor’easter that developed over the Gulf of Mexico and then crossed the SE U.S. and tracked up the East Coast.

The storm currently in the Atlantic is not expected to have a negative impact on Western North Carolina. In fact, our weather is expected to improve into the weekend. However, it looks like we will have another significant system impact our weather early next week.

* NOAA’s Environmental Visualization Laboratory and NOAA’s National Weather Service Hydrometeorological Prediction Center

 ** http://en.wikipedia.org/wiki/Nor%27easter

 

November 1, 2012

A totally different world - just up the road

The snow that fell in Western North Carolina this week due to Hurricane Sandy was mainly isolated to the higher elevations and unless you’ve been up in the mountains in the last couple of days, it’s hard to appreciate just how much snow the area received.

The map of the region below will help to illustrate where the snow occurred. The areas with the aqua color on the map received some snow, anything from a trace up to 6” during the event. But as you increase in elevation along the mountain ridges that form the state line between North Carolina and Tennessee, the snowfall totals increase dramatically with the bright pink representing 20-27” and the areas in white receiving up to 36” of snow.

Why did the higher elevations get hammered while there was very little, if any snow in the valley?  Blame a process called orographic lift.

As a cold air mass approaches WNC from the north or northwest, those tall mountains along the NC/TN state line force the air mass to rise over the mountains. As the air is lifted over the mountains, it cools dramatically, saturating the air, and causing precipitation to form, usually as snow.  This effect can be very localized and often results in very high snowfall totals along and just downwind of the ridges. 

The result . . .lots of snow!  This rhododendron at 4000’ shows the impact of what an 18” snow can do.

And you may remember the view below from last week’s e-mail . . .

There’s nothing like experiencing three seasons in a single month!

The good news is that the early November sun and slightly warmer temperatures into the weekend should help to melt the fallen snow. The not so good news  - next week could bring more unseasonably cold and stormy weather and . . . remember that this weekend is the end of Day Light Saving Time.

 

October 25, 2012

My, how things change!

One of the most amazing things about living in Western North Carolina is the ability to watch the Earth system move through its annual climate cycles. That is especially true for those of us who have moved here from other regions  - regions that perhaps do not progress through these cycles in such grand fashion.

The images below highlight how fast the changes occur in our mountains. Frozen Knob is a mountain in Madison County that shows great color each fall.  Color had just started to appear on the mountain on October 11th, but by this week, the greens are giving way to the yellows, oranges and rusts of fall.

The ever-watchful eyes of NASA’s Earth Observing System can make it possible for us to appreciate these annual cycles from the vantage point of 440 miles above the Earth, thanks to the MODIS (or Moderate Resolution Imaging Spectroradiometer) instrument aboard the Terra satellite. The image below was taken just before 12:30 p.m. on Wednesday of this week, as the Terra satellite passed overhead.

You can see the amber color of fall across the mountain slopes and if you look carefully - you can even see the dark colors of the spruce-fir forests that dominate the highest elevations of the Great Smoky Mountains, the Black Mountains and the Pisgah Ridge.

Image Credit: NASA and the Space Science and Engineering Center (SSEC) at the University of Wisconsin-Madison

These next couple of days may be the last chance to catch this year's fall colors at the mid-elevations. A big change in the weather is coming this weekend as significantly cooler air will move in with a cold front. So, make the time to get out and enjoy the sights!

 

October 18, 2012

Nature's Fall Color Palette

For those of us who consider ourselves to be "visual" people - fall can be simply overwhelming.  Everywhere we look, there's something else that takes our breath away.

To me, one of the prettiest sights this time of year is a tree that still has green leaves, but is also boldly  displaying leaves of yellow, orange and red, too. Our maple trees are very good at displaying this full palette of fall colors -  all in one convenient compact spot.  If you look, you will see many on display in Asheville this week.

The fall colors that we see in the leaves are the result of the breakdown of the chlorophyll that provides the leaves with their typical green color. This process is started by the increasing length of night and shorter daylight hours that we start to experience in late summer and early fall.  As the trees prepare themselves for winter, the production of chlorophyll slows and then stops. The result is that green is no longer the dominant color, and the other colors in the leaves become visible.

If you enjoy the golden glow provided by the yellow leaves in the fall forest, you can thank the yellow pigments in the leaves  - called xanthophylls - for the beautiful display.(The word comes from Greek: xanthos - yellow  and phyllon - leaf.)

The vibrant orange leaves are the result of orange pigments called carotenoids and the vibrant reds and purples are the result of pigments knows as anthocyanins. If you would like to learn more about the science of autumn color, click here.

Whatever your favorite, the colors are really beginning to put on a show at the mid-elevations and this weekend may be one of the best opportunities to get out and enjoy the show. Following the passage of a cold front late today, the weekend weather looks like it should be perfect for getting out and exploring the countryside.  Be sure to bring your camera  . . . and a jacket!

This weekend also brings a chance to catch an early morning meteor shower that has a history of putting on quite a show.  The Orionid meteor shower will peak very early on Sunday morning, October 21st as the Earth passes through the debris of Halley's comet. The best time to look is several hours before dawn on Sunday morning. So, grab a blanket, a coat and some strong coffee(!) and head outside.  Find a comfy spot to lie down and look high overhead at the constellation Orion. You'll find more information on the meteor shower here.

October 11, 2012

Inversion and balloons on a calm fall morning

Fall brings many changes to Western North Carolina, from the turning of the leaves - to the turning up of the thermostat. These cooler nights mean that many of us are heating our homes with wood-burning stoves and fireplaces to ward off the chill. Most of the time, the wood smoke (along with other particulates that are in the air) mix through much of the lowest layer of our atmosphere, called the troposphere.  But when the air is cool and the winds are calm, we can occasionally see those tiny particles concentrated in the early morning air under what meteorologists call a radiational temperature inversion. Such was the case this morning, as you can see in the image below from Madison County, looking to the southeast across the valley toward the Craggies (image center) and the Blue Ridge Parkway.

Our atmosphere is divided into layers that are largely based on how the temperature changes with height within that layer. In the troposphere, the layer that we live in, the temperature typically decreases with height.  You've probably been subjected to that if you've ever visited the higher elevations and forgot to bring your jacket.  Yikes! Typically, it is noticeably cooler on the ridgetops than it is in the valley below. However, there are occasions when that normal temperature profile flips, and the cooler, heavier air collects in the valley - like it did this morning.  

The clear skies and calm winds that we had overnight caused the air closest to the ground to cool faster than the air above it (the result of radiational cooling). In addition, the calm winds meant that there was no wind to help mix things up. The result - a temperature inversion formed, trapping the layer of cooler, heavier air (and everything in it) close to the ground.  This type of inversion typically does not last for too long. As the sun climbs higher in the sky and warms the ground, the air mixes and the atmosphere returns to its typical structure, no longer trapping the particulates close to the ground.

This morning's calm winds also created ideal conditions for hot air ballooning.  Looking south toward Mt. Pisgah and Frying Pan Mountain, I could see four hot air balloons enjoying the perfect flying conditions. I've labeled each of the balloons below. The first two are flying above the inversion and can be seen in the clear air. However, three and four are in the inversion layer and may be difficult to spot.  In this image, in addition to the inversion layer, you can also see some fog still lingering along the path of the French Broad River

You may have the opportunity to spot additional radiational temperature inversions this fall. They do occur most frequently in the cooler months than during the summer.

 

October 4, 2012

Early fall color at the higher elevations

It really is a magical time of the the year - as our once deep green mountainsides begin to show their fall color.  The reduced hours of daylight have triggered the deciduous trees to start preparing for the coming winter and, at times, it seems like the changes happen so quickly that you can see them occur overnight. I took the image below this morning - amazed at just how fast these trees seem to be changing.

The days of longest daylight in Western North Carolina, during late June (around the summer solstice), have about 14 hours and 34 minutes of daylight.  Now, during early October, our days are already much shorter, down to 11 hours and 41 minutes of daylight. That's 2.8 hours less daylight than we had in June, quite a difference!

As the temperatures continue to trend downward we will be witness to one of nature's most amazing shows as our mountains put on a visual spectacle second to none over the next month.  Enjoy the show!!

September 27, 2012

Fog - from up, down and all around!

Fog has been a common morning feature across the valleys in Western North Carolina for much of the summer and early fall.  And while fog causes concern for travel because it reduces visibility, could it also be possible that the fog may be warning us of the coming winter?

The French Broad River Valley was coated with a thick blanket of of fog and low clouds this morning, as you can see in the picture above that I took at around 9:00 a.m. This image was taken at 4000 ft, not far from Mars Hill, looking southeast into North Buncombe County.

Fog occurs in the morning when the air close to the ground cools overnight and becomes saturated (it's relative humidity reaches 100% - so the water vapor in the air condenses and creates tiny suspended water droplets,  a.k.a. - a cloud on the ground).  Our region has received quite a bit of rainfall this summer, so there has been ample moisture available to create the fog during most mornings.

Did you count the number of foggy days in August?  There were quite a few. By one report coming from North Buncombe County - at least 18 of them.  The National Weather Service reporting location at the Asheville Regional Airport recorded 27 days in August that had fog, and during 14 of those days - the fog was thick enough to reduce visibility to less than 1/4 mile. Why? What's the big deal with fog?

There's an old weather lore saying that states:

For every fog in August,
There will be a snowfall in winter.

Ummm . . . ooops!

The image above captures the last of this morning's fog suspended over sunflowers that were so beautiful and bright that I'm thinking anything but winter snow.  However, it does cause one to wonder - could the old weather lore statement be right?

Only time will tell . . .

If you are interested in learning more about what we can expect for the coming winter, mark your calendar for Thursday, November 8th. The Institute is hosting a free seminar on the extended winter weather forecast. More details to come - but an event not to be missed

September 20, 2012

Lots of Water!

The beginning of this week started with significant rainfall over the region thanks to a large weather system that dumped a record amount of rainfall in Asheville on Tuesday and provided more rain in two days than we usually expect during the entire month of September!  Our area's rivers and streams are doing their job of transporting that water downstream - but the evidence of all that moisture was still hanging around early this morning in the form of low clouds.  I shot the image below earlier today (9/20/12) as the clouds were beginning to break at 4000 ft - revealing the early fall color that is starting to appear on ridgetops.

Locally, the heaviest rains during this week's event fell southwest of Asheville in Transylvania, Jackson and Haywood Counties where some locations received over six inches of rain as indicated by the red colors in the image below. The picture shows the total estimated rainfall during the entire event so you can get a good look at how much rain our region received Monday and Tuesday. Note the large area in East Tennessee that saw over 6" of rain. The scale to the right of the image is in inches.

Image: NOAA’s National Weather Service, Southern Region Headquarters http://www.srh.noaa.gov/ridge2/RFC_Precip/

The Asheville Regional Airport (AVL) set a new daily maximum rainfall record of 3.28" on Tuesday, 9/18, shattering the old record of 1.72" set on that date in 1906. The image below shows how much rain the local area received during the two day event, including the 4.38" total that AVL received Monday and Tuesday. The normal rainfall for AVL during the entire month of September is 3.81" inches.

Image: NOAA’s National Weather Service, Southern Region Headquarters http://www.srh.noaa.gov/ridge2/RFC_Precip/

We officially turn the corner from summer into fall this Saturday morning at 10:49 EDT.  At that time, the autumnal equinox occurs, marking the transition into autumn for the Northern Hemisphere when the tilt of the Earth's axis will mean that the Southern Hemisphere will now begin to receive more of the sun's energy. (Mom always did say that it is was nice to share.) While the end of summer comes as good news to many folks who saw record high temperatures and extended drought over the summer, personally - I hate to see the long hours of daylight go.  You may have already noticed that the sunrises are coming later and that sunset is coming earlier each evening. . .  a sure sign that fall is about to begin.

September 13, 2012

The First Signs of Coming Change . . .

The bright yellows of Goldenrod are now plentiful in fields and along roadways in Western North Carolina; last weekend’s cold front brought cooler and drier air into the region; and you may have noticed that some of the leaves on the trees are beginning to lose their deep green color. These first signs of the coming autumn are a welcome sight to many of us who claim fall to be our favorite season. (Just don’t remind me that the vivid colors of fall are all too quickly followed by winter!)

The autumnal equinox, the official beginning of fall, is still over a week away but deciduous trees and shrubs across the region are beginning to respond to the decreasing hours of daylight by slowing down the production of chlorophyll. Chlorophyll is what gives leaves their green color and you can see the darker greens of summer being replaced by lighter greens as the trees begin the annual process that will eventually lead to the dropping of their leaves.

Another sign of the change – the stratification (layering) of the atmosphere that was visible over the French Broad River Valley this morning.  In the image above, you can see the fog that had developed overnight across much of the valley, the result of calm winds and air that cooled to the point of saturation overnight.  But you can also see the Planetary Boundary Layer (PBL) as the dark layer above the fog.  If you’d like to learn more about the PBL – see the Fun facts e-mail here dated August 31, 2011. 

As we are nearing the autumnal equinox, the Northern Hemisphere is receiving less direct energy from the sun. One of the effects of this is that it takes longer for the sun to heat up the ground and this reduces the mixing of the air close to the surface – making the fog hang on a little longer and occasionally making the PBL visible from higher elevations, as it did this morning.

We are expecting another cold front to move into the region this weekend, and the Climate Prediction Center is forecasting below average temperatures to continue for much of the Central and Eastern U.S. through the last week of this month, as indicated by the blue colors in the image below.

Image Credit: NOAA's National Weather Service Climate Prediction Center

If this forecast holds – it could help to set Western North Carolina up for a vivid display of fall colors. Now that we've had a good growing season with no extended periods of drought, a period of cool nights and mild sunny days will help to develop great color in the fall.

 

August 29, 2012

Isaac -Taking the Coast by Storm (at night!)

Image credit: NASA Earth Observatory image by Jesse Allen and Robert Simmon, using VIIRS Day Night Band data

This amazing image of Tropical Storm Isaac was captured just after midnight on Tuesday, August 28th by the Visible Infrared Imaging Radiometer Suite (VIIRS) on the Suomi-NPP satellite. Still off the Gulf Coast, Isaac’s clouds were lit by moonlight and the lights of cities across the Southeast U.S. are clearly visible. I’ve added labels for some of the more visible metropolitan areas, including Asheville.

At the time this image was taken, Isaac was a Tropical Storm with maximum sustained winds of 70 mph.  The storm was upgraded to a hurricane just before noon on Tuesday when its winds were reported at 75 mph.

Isaac moved on shore at 7:00 P.M. last night (Tuesday 8/29/2012), and was downgraded to a Tropical Storm at 2:00 P.M. this afternoon.  However, it is important to note that while a Category 4 or 5 hurricane seems so much more dramatic than a plain ‘ol tropical storm, the real danger from these tropical systems is often from the amount of storm surge and inland flooding that they produce. So don’t be fooled by the downgrading of the storm and its potential to do harm.  (Remember what Tropical Storm Allison did to Houston in 2001?) Isaac is a very slow moving storm and that increases the danger of flooding as it is expected to produce over 14” of rain in some areas.

Will we see rain in Western North Carolina from Isaac? Scattered showers and thunderstorms have developed this afternoon over the area thanks to a surface front that has been lingering over WNC. The latest forecast from NOAA for rainfall associated with the storm, below, indicates that most of the rain will occur well to our west. The forecast below is for the total rainfall expected through Monday morning of next week, in inches. However,  I encourage you to keep a watchful eye on the forecast as we head into the upcoming Labor Day weekend as we may see locally heavy rain here as well – especially in the mountains.

Click here for more information on the rainfall forecast above.

 Click here for the original release by NASA Earth Observatory for more information about the satellite image

August 16, 2012

The Lush Forests of Western North Carolina

The forests that blanket Western North Carolina go through a yearly cycle of growth that can often occur unnoticed by most of us until we see the colorful displays of leaves in the fall . . . or have to fight the non-stop weeds of August.

The ever-watchful eyes of NASA’s Earth Observing System can make it possible for us to appreciate this annual growth cycle from a new vantage point, thanks to the MODIS (or Moderate Resolution Imaging Spectroradiometer) instrument aboard the Aqua and Terra satellites.

The image below was taken this past Sunday (8/12/12) as Terra was passing overhead around 12:30 in the afternoon. The image shows the lush dark green forests of late summer, as well as some interesting features including key roads in the region.

Image Credit: NASA and the  Space Science and Engineering Center (SSEC) at the University of Wisconsin-Madison.

You can also see an interesting fishbone-like pattern to the cumulus clouds west of Asheville. The clouds most likely formed along the higher peaks as the terrain heated in the sun, a common occurrence during the summer months. 

If you’ve been receiving the Fun Facts e-mails for a while, you may remember the images below from The Greening of the Mountains  e-mail sent on May 3, 2012.  These images from the Aqua satellite help to provide some perspective to this annual cycle of growth.  The image below, from April 28, 2012 shows the bright greens of spring, with the exception of the higher elevations which still appear dark brown.

Image Credit: NASA and the  Space Science and Engineering Center (SSEC) at the University of Wisconsin-Madison.

Those bright greens of spring are in sharp contrast to the late winter image below, from March 1 of this year that shows the still brown, pre-spring landscape.

Image Credit: NASA and the  Space Science and Engineering Center (SSEC) at the University of Wisconsin-Madison.

Most of Western North Carolina has received near normal rainfall this year and the USDA Forest Service reports that our forests are generally in good health as a result. However, Jason Rodrigue, USDA Forest Service Silviculturist here in Asheville notes that the late-spring freezes that most of us endured this year may have a negative impact on the acorn crop both this year, as well as next.

(BTW – silviculture is a branch of forestry that deals with the development and care of forests.  I had to look it up.)

August 9, 2012

The Haves and the Have Nots . . . and meteors to boot!

The story of this summer has certainly been that of climate extremes. In Western North Carolina we’ve had quite a bit of rain while well over half of the lower 48 states remain in drought. Our moist summer has produced jungle-like conditions in many of our yards, but has also produced some breathtaking sunsets with all the moisture in the air.

It’s not uncommon to see fog in the valleys during the morning hours, but this image of valley fog looking north toward the North Carolina/Tennessee state line is from Monday evening (8/6/12) following the heavy rainfall throughout the area.

You may have read that NOAA’s National Climatic Data Center just released data that puts this July as the hottest month on record for the U.S. with the average temperature of 77.6° F, besting the previous record set in July of 1936 by 0.2°.  July in Asheville was hotter than normal as well, with the average monthly temperature of 76.8°. That is 3° warmer than our July normal.

So – what is a climatological  “normal”?  Simply put – a normal is the average value over the previous 3 decades. For example – when you hear that the normal high temperature for today is 84°, that means that during the time period of 1981-2010, the average high temperature on August 9th was 84°. The National Climatic Data Center in Asheville calculates the normals for locations across the county every 10 years – using the previous 3 decades. Beginning in the year 2021, we will be using normals that were calculated over the time period of 1991-2020.

We will continue to add rain in area rain gauges over the next several days, but a cold front is expected to move through the area on Saturday, helping to clear out the skies. This should set us up for a nice opportunity to view the peak of the annual Perseid  meteor shower on Saturday night!  Find a dark location away from city lights, give your eyes time to adjust to the night and look to the northeast.  The Perseid meteor shower occurs every August when the Earth moves through the debris left by the comet Swift-Tuttle and it’s a good year to view the meteors without interference from the moon which won’t rise until after 2:00 A.M.

Check these websites for additional information:

 The U.S. Drought Monitor http://www.drought.gov/portal/server.pt/community/drought_gov/202

 NOAA’s NCDC State of the Climate: http://www.ncdc.noaa.gov/sotc/

 NOAA’s Climate Normals:  http://www.ncdc.noaa.gov/oa/climate/normals/usnormals.html#WHATARENORMALS

 

August 2, 2012

Mammatus and Towering Cu

Thunderstorms are nature’s engine. They are an amazing example of the energy that is produced in our atmosphere as water vapor condenses into water droplets, and they serve the very real purpose of taking heat from the surface of the planet and moving it higher into the atmosphere. 

Wednesday evening, around sunset, there were a number of thunderstorms to our north in Tennessee. Most of these storms dissipated before moving into Western North Carolina – but the anvils, the top portion of the thunderstorms, were visible –and they put on quite a show.

In the foreground of the image above– you can see what meteorologists call “towering cu” – short for towering cumulus. Cumulus, (Latin for “pile”) are clouds that appear heaped and lumpy – and they’re almost a daily occurrence in our summer skies.  Towering cu are cumulus clouds that are developing vertically – creating a tower. Behind the towering cu you can see the soft billowy structure of the mammatus clouds. These downward hanging cellular clouds form on the underside of thunderstorm anvils and are an amazing sight that are often associated with severe thunderstorms.

Aside from putting on a show of interesting clouds, Wednesday’s thunderstorms also highlight an interesting and fortunate fact ( . . . fortunate for us) about this summer’s weather pattern.  You may have noticed that many of our thunderstorms this summer have been moving from the northwest to the southeast. You can see this motion in the short clip of Wednesday (8/01/12) evening’s radar images below.

Credit: Animation created using images from NOAA’s National Climatic Data Center http://gis.ncdc.noaa.gov/map/cdo/

While this northwest to southeast motion is not unusual – it is not the typical pattern for us this time of the year when many of our storms tend to move into our area from the south. The reason – blame the same ridge of high pressure that has brought the heat wave and drought to the Central U.S.

As I’ve drawn in the image below, the circulation around a ridge of high pressure in the northern hemisphere is in a clockwise motion.  It is that motion around the persistent ridge in the Central Plains that is helping to steer the thunderstorms you can see in the radar animation.

A ridge compresses the air beneath it, heating it up and reducing its relative humidity, greatly reducing the ability for rain to form.  All of which has led to one of the worst droughts on record.  And while the area under the ridge is subjected to heat and drought, those locations on the outer edges of the ridge can experience something entirely different.

The region where cooler and moister air interacts with the hot air of the ridge is often dubbed the “ring of fire” by meteorologists because this is where instability helps to fire-up thunderstorms. So far this summer, that has been the case across much of the Ohio and Tennessee River Valleys stretching down to the Central Gulf Coast. You can clearly see which areas experienced above normal rainfall in July, indicated by the blue and purple areas in the image below, as well as those that saw below normal rainfall shown in yellow, red and orange.

Image Credit: NOAA’s National Weather Service Advanced Hydrologic Prediction Service http://water.weather.gov/precip/

So, again, those of us in Western North Carolina should be thankful for each drop of rain we receive as the chance for additional rainfall continues in our forecast over the weekend.

 July 26, 2012

The Mysterious Disappearing Rain

The scattered thunderstorms of this week have created several opportunities to witness a weather phenomenon that you may have seen a number of times, but didn’t quite know what to call it.

In the image above, the setting sun brought a beautiful glow to the clouds and helped to illuminate what appears to be rain falling from the cloud – but where did the rain go? It seems to disappear before it reaches the ground.

You can see a similar situation with the rain that is falling out of the bottom of the remnants of the thunderstorm in the image below.

 

Just 15 minutes earlier, this was a vigorous storm, but as the storm weakened, it eroded from the bottom up – leaving a still menacing looking anvil top . . . and shafts of virga.  Virga (Latin for “rod”) is precipitation that falls from a cloud, but that changes into water vapor before it reaches the ground.  This occurs when the precipitation, which can be liquid as rain, or frozen as snow or ice particles, passes through a layer of dry air.

Virga is a fairly common occurrence in Western North Carolina, and is very common in the Western U.S. where the climate is much more arid.

So – the next time you see it, you’ll know what to call it, impressing your friends and family with your geekiness.

July 19, 2012

A stormy pattern – but so much better than the alternative!

It’s hard to overstate the importance of water to the Earth’s climate system. Water in its three phases - liquid, solid and gas, helps to drive our local weather as well as our regional climate. Most of us don’t think about plain ol’ water too often, but it’s when we have too much or too little of this precious resource that we really pay attention to it.

Much of Western North Carolina has enjoyed near normal rainfall so far this summer, thanks in large part to the thunderstorms that blossom in the heat of the afternoon sun.  The image above is of thunderstorms that developed along the escarpment, east of Asheville, last week as the late-day sun was catching the tops of the storms.

The chance for storms will continue in our forecast for the foreseeable future, a forecast that most of the rest of the country would be happy to have as severe drought grips much of the nation.  

In the U.S. Drought Monitor below, you can see that a significant portion of the county is experiencing drought that is classified as Severe (medium brown), Extreme (red) and even Exceptional (dark brown).

The U.S. Drought Monitor is produced by a partnership between the U.S. Department of Agriculture, the National Drought Mitigation Center, and NOAA’s National Weather Service (NWS) and the National Climatic Data Center (NCDC). NOAA’s NCDC is located right here in Asheville.

On July 11, the United States Department of Agriculture announced that more than 1,000 counties in 26 states qualified as natural disaster areas—the largest total area ever declared a disaster zone by the agency.1

So – what does the long-term forecast hold for the drought-stricken area? The U.S. Seasonal Drought Outlook below shows some improvement in the Southeast and Southwest U.S. indicated by the green and green-brown hashed areas. But a disturbingly large portion of the U.S., shown in brown, is expected to see the drought continue or even intensify with development of drought conditions expected in the yellow areas.

Image Credit: NOAA’s NWS Climate Prediction Center

In short – enjoy the rain. There are many across the country who only wish that they too could have a scattered thunderstorm or two.

1 Drought Grips the United States  http://earthobservatory.nasa.gov/IOTD/view.php?id=78553&src=eoa-iotd

July 12, 2012

When it rains – it pours (at least for some)!

The stalled frontal boundary that is lingering over the Southeast U.S. has provided some much needed rainfall from Texas to the Atlantic Ocean – but some folks in Western North Carolina saw too much of a good thing on Wednesday when over 3 inches of rain fell in areas of both Buncombe and Madison Counties.

The image below is a look at observed rainfall for the past 2 days created by NOAA using the network of Doppler radars and rain gauges. Using the scale to the right of the image, you can see that areas in pale yellow have received over 2.5’ of rain so far and those in bright yellow have seen over 3”- including Downtown Asheville. You’ll also notice the areas in blue where less rain has been observed - like the 0.61” that has been recorded at the Asheville airport, south of town near Fletcher, over the same time period.

Image: NOAA’s National Weather Service, Southern Headquarters http://www.srh.noaa.gov/ridge2/RFC_Precip/

So – how are we fairing on rainfall so far for the year? The image below shows the departure from normal for the year so far.  While most of Buncombe and Madison Counties are fairly close to normal, within 2-3”, some areas are actually slightly above normal (thanks to yesterday’s flooding rainfall). The counties southwest of Asheville are significantly drier, as indicated by the dark red colors.

Image: NOAA’s National Weather Service, Advanced Hydrologic Prediction Service http://water.weather.gov/precip/

The forecast calls for more rain because the stalled front is not expected to go anywhere soon.  Please try to stay on top of what is happening with the weather over the next several days, especially into the weekend. Saturated ground will mean that locally heavy rain may cause flash flooding and the possibility of downed trees.

I highly recommend bookmarking this website for fast access to the national weather picture:

http://radar.weather.gov/Conus/full_loop.php

June 21, 2012

The Reason for the Seasons

Last evening (6/20/) at 7:09 p.m. EDT, we officially entered summer as people across the Northern Hemisphere noted the summer solstice. The summer solstice occurs at the point-in-time when the Earth’s northern axis is at its greatest tilt toward the Sun. It is because our planet is tilted on its axis of rotation by about 23.5° degrees that we experience seasons. As you can see in the image below – the Northern Hemisphere is tilted toward the Sun during our summer, and away from the Sun during our winter. (Look below for the winter solstice e-mail from December 21, 2011 “Bring on the Light”.)

Image: NOAA

The result of the Earth’s tilt is evident if you take careful note of where the Sun rises and sets on our horizon throughout the year. The panoramic image below is of the eastern horizon from a peak in Madison county where I’ve been carefully watching the sun make its trek throughout the seasons. It really is amazing what a difference it is.

So, enjoy the long summer days. Both yesterday and today have the longest hours of daylight for the year in Asheville: 14 hours, 34 minutes and 4 seconds. Compared to the 9 hours and 45 minutes of daylight we see on the shortest day at the winter solstice – that’s a big difference – and reason enough to celebrate this amazing place that we live. 

Happy summer!

June 13, 2012

Could the real treasure be rain?

Showers and thunderstorms moved through Western North Carolina last evening bringing some needed rainfall and a quick peek at a rainbow – and it looks like this afternoon may bring more of the same.  Good thing – we need the rain, but we’re not doing too badly compared to our neighbors to our south and southwest.

Officially, at the Asheville airport we are  0.93” behind on rainfall for the year (on 6/13/12). The map below shows departure from normal rainfall over the last 30 days. That means that anything in green, blue, or purple has had above normal rainfall. Anything in yellow, orange and red is dryer than it normally is.  You can see that the metropolitan area of Asheville has received enough rainfall over the past 30 days to be slightly above normal, shown in green and blue. However, you’ll notice that there is quite a bit of orange and red (indicating 3”-8” below normal) in Henderson, Polk, Transylvania, Jackson, and Haywood Counties.

Over the Southeast U.S., it’s the same story – feast and famine. The recent flooding rainfall that fell over parts of Florida and the SE shows up well on the map below, but much of the region is still in drought.

Could relief be on the way?  It may be.  The La Nina has gone away and NOAA issued a statement last week that there is a 50% chance that El Nino may appear before the end of the year (more details on that in a future e-mail.)  El Nino typically means a wetter and cooler period over the SE U.S., especially in the winter months. So, relief may be coming.

June 6, 2012

A rare event gives us some perspective.

Life is crazy, busy, I know. We get so focused on daily activities that we often forget what a wondrous and amazingly large universe we live in. Occasionally, we get a glimpse of that reality and it never fails to leave us awestruck. Such was the case last evening (6/5/12) when we were treated to a rare event when we were able to see one of the two inner planets of our solar system, Venus in this case, pass in front of our Sun, an event called a transit. That means that the Sun, Venus and our Earth were all aligned as seen in the image below.

Image generated using NASA’s Eyes on the Solar System

Solar transits are rare events, the next transit of Venus won’t occur until 2117, but the real message of last evening’s event . . . we are so very small and so special in the vastness of space. 

Even though it’s almost 93 million miles away, our Sun is the driver of our seasons, our climate and the daily weather on this planet. In the image below, Venus, similar in size to our Earth, is nothing but a small dark dot as it crosses the face of the Sun.

The Sun set over Western North Carolina in mid-transit last night, with distant cumulus clouds starting to obscure the Sun.  Bringing us back to our small planet, in a very big neighborhood.

May 24, 2012

Solar Eclipse – Special Delivery!

A fascinating spectacle occurred on Sunday, May 20, but only locations in the Western and Central U.S. where treated to the rare annular solar eclipse on Sunday evening, May 20th.  Fortunately, I was able to capture it as I was visiting the West Coast on vacation.

The image below is a composite of five images that I shot over the course of the 2 hour event showing the progression of the Moon as it moved across the Sun. The eclipse started as the Moon began crossing the lower right section of the solar disk, looking as if someone had taken a bite out of the Sun (!). At the peak on the eclipse, the moon covered enough of the sun to make it look like a crescent (center), then the moon exited toward the upper left.

An annular solar eclipse occurs when the Moon sweeps in between the Earth and the Sun, but unlike a total solar eclipse when the Moon completely blocks out the Sun, the annular eclipse blocks only a portion of the Sun. (The term annulus is Latin for “little ring”.) This occurs because the Moon’s orbit around the Earth is not a perfect circle – but is actually an ellipse. During this particular pass in between the Sun and the Earth, the Moon was too far away from the Earth to completely cover the disk of the Sun. This meant that those who were within the center-line of the eclipse (about 200 miles wide), were treated to the ‘ring of fire’ as the Moon covered up to 94% of the Sun, creating a black hole in the center of the Sun. I was not within that center-line that stretched from Northern California to the Texas Panhandle, but the view from Griffith Observatory in Los Angeles was truly amazing as about 85% of the Sun was blocked at the height of the event.

Perched on top of the roof of the observatory, I got a birds-eye view of the crowd and numerous television crews who had gathered to witness the historic event. You can just barely make-out the famous “Hollywood” sign on the mountain to the left, under the large tower.

By the time the sun set – we were back to a full solar disk – and a beautiful view of the iconic sign.

So – when is our next opportunity to witness a solar event here? We’re in luck! On June 5, 2012 we will be able to see the planet Venus as it crosses directly between the Earth and the Sun, called a transit. As the transit of Venus occurs around sunset on the 5th, the planet will be visible as a small black dot crossing the face of the sun.  Click here for more information from NASA. But the big event, a total solar eclipse will occur in August of 2017 and the “path of totality” will pass just to the south and west of Asheville! (Look here for detailed maps.) The most important aspect of viewing any solar event, is to protect your eyes. You should NEVER look directly at the Sun. We used protective solar viewing glasses like these (they even worked as a great filter for my camera!).

May 11, 2012

Sunset, Solar Pillar and Contrails . .  . Oh My!

Western North Carolina has been enjoying some beautiful weather since the rain moved out on Wednesday.  Those mostly clear skies set the stage for a beautiful sunset on Thursday evening (5/10) – with some atmospheric optics to boot!

The image above was shot about 4 minutes after the sun dipped below the mountain last night.  The high, thin, wispy clouds painted gold by the setting sun are called cirrus clouds and are made of ice crystals (as opposed to liquid droplets that makes up most other clouds, including the darker clouds to the right). Also visible are at least 10 contrails (short for condensation trails) produced by condensation of water vapor in the exhaust of aircraft jet engines.

The six-sided, plate-like ice crystals that form the cirrus clouds can create some very interesting optical phenomena, depending on how they are aligned within the clouds. In this case – the crystals are aligned horizontally, so that the light from the sun reflects off of the bottom side of the crystal, creating a vertical solar pillar. When the crystals are alligned vertically – we can see sun dogs (see the October 27, 2011 account by scrolling down).

Weatherlore says that the appearance of solar pillars, sundogs, and halos may herald the coming of stormy weather in a few days.  In this case – it’s true. We’ll likely see more cirrus clouds this evening and tomorrow, ahead of the storm system that is expected to bring rain into the region over the weekend. So – keep you eyes on the sky and perhaps you’ll see some interesting sites tonight around sunset.

May 3, 2012

The Greening of the Mountains

One of the most amazing transformations in nature is on display right here in Western North Carolina as trees and vegetation come alive in the spring. This process occurs over a period of time with the lower elevations “greening up” first. The flush of color then moves up the mountains where the highest elevations are the last to fill out, thanks to generally lower temperatures at the higher elevations.

While it has been green in the valley for quite a while, the trees at the higher elevations (4000 ft and above) are still in the process of waking up from winter. This transformation is visible thanks to NASA’s Aqua Satellite, part of the Earth Observing System that allows us to monitor the Earth.

The image below was taken on March 1, 2012 – a beautifully clear day that allowed a clear view of the brown, pre-spring landscape.

Image Credit: NASA and the  Space Science and Engineering Center (SSEC) at the University of Wisconsin-Madison.

By last week (April 28th)– the landscape had transformed into a lush green spring paradise seen in the image below, with the exception of the higher elevations which still appear dark brown.

Image Credit: NASA and the  Space Science and Engineering Center (SSEC) at the University of Wisconsin-Madison.

The forests of Western North Carolina play an important role in our local climate and even our daily weather conditions.  The green vegetation helps to hold moisture in the soil by shading the forest floor. But the plants also transpire significant amount of water vapor into the atmosphere, making muggy air and the puffy cumulus clouds seen in the picture above an almost daily occurrence. This added moisture also helps to aid in the formation of the afternoon thunderstorms that we see in the mountains during the warm months.

April 24, 2012

April Snow!

The Black Mountains didn’t live up to their name on Monday afternoon, blanketed with about 2” of snow.

While snow in April is not unheard of in Western North Carolina – this past weekend’s snow event seemed out of place, partly because we had such a warm March this year.  Many folks reported seeing snowflakes in and around Asheville on Sunday, but it was the higher elevations where there was enough snow to accumulate, turning spring back into winter – at least temporarily.

The map below shows where most of the snowfall accumulation took place across the region. Areas in white received at least a dusting of snowand the darker blue colors indicate where the heaviest snowfall occurred.

 April 19, 2012

Spring rains . . . and there’s more on the way!

Map: NOAA’s National Weather Service

Showers and thunderstorms brought some needed rain to Western North Carolina this week – but, as usual, it was all about . . . LOCATION, LOCATION, LOCATION.

The official reporting location for Asheville’s weather is at the AVL airport, south of town, where they recorded a total of 2.16” of rain over the 2 day event.  You’ll notice on the image above that the recorded value corresponds well with the darker green pixels on the map indicating that between 2.0 and 2.5” of rain fell.  You’ll also notice that a good portion of Buncombe County received between 2.5” to 4” of rain, as indicated by the shades of yellow. 

This helps to illustrate that what is recorded at the airport (or any single point) is often not representative of the entire area. Even with the recent rain, AVL is still reporting 1.17” below normal rainfall for the year.

This is a common issue with in situ measurements (Latin, meaning “in place’) and is a good example of why weather radar and other forms of remote sensing (like satellites) are so important to providing a more complete view of weather and climate information. The image above was generated using the National Weather Service’s radar and rain gauge data combined to provide a more accurate picture. You can visit the website here.

So how does the region look for rainfall so far this year?

The image below shows the percent of normal precipitation since January 1 of this year, and indeed, most of the state is dryer than normal as the orange and yellow indicate below normal precipitation. Those of us in the mountains are faring better with year-to-date rainfall closer to what we would normally expect, and even a few locations with above normal levels as shown in green.

Map: NOAA’s National Weather Service

A scattered shower or thunderstorm is possible today and tomorrow – but there is a much better chance for more significant rain over this coming weekend. So, perhaps we’ll reduce the deficit at the airport.

April 4, 2012

Spring Storms Create a Foggy Morning

Spring brings the return of afternoon thunderstorms, but the impact of the rain can last long after the storms move on.

Yesterday’s thunderstorms left the mountains moist as the sun set, producing the blue ridges that this part of the world is so famous for.

However, the wet ground set us up for some thick fog this morning as the moisture condensed into fog across the French Broad River Valley. With clear skies overhead, it didn’t take long for the sun to heat the air enough to burn off the fog. You can see the process in the short animated clip of this morning’s visible satellite images below.

Satellite Images: NASA MSFC Earth Science Office GOES-E CONUS Visible Satellite Data

As you watch the clip, pay attention to the motion of the clouds near the North Carolina and Tennessee state line, north and west of Asheville.  These developing cumulus clouds are the first indication of the thunderstorms that are beginning to develop again this afternoon.

While we’re talking about thunderstorms, here’s your warning. The storm system that produced the severe thunderstorms in Dallas and Northeast Texas yesterday will be moving into the Southeast U.S. tomorrow. This will increase the risk of severe weather over the Carolinas tomorrow. So, please stay weather alert.

March 29, 2012

A Few of My Favorite Things . . .

The evening sky holds many wonders – but few are as wondrous as getting to see some of the brightest objects in our sky all clustered together. Such was the case last night when the crescent moon was accompanied by the brightest planets in our sky along with the constellation Orion and the bright star Sirius.  An amazing site that you may be able to catch again this evening if you look to the west after the sun sets.

The crescent moon is growing in size each night, so it’s called a waxing crescent. (In the image above, the 30 second exposure time has caused the moon to appear a bit smeared, hiding its crescent shape.)   To the lower-right of the moon are the two brightest planets in our sky, Venus and Jupiter. Venus –is the brightest object in our sky, other than the moon and our own sun.  Jupiter, the next brightest, is the largest planet in our solar system and you can easily see several of its moons using a pair of binoculars.

My favorite constellation of all, Orion (sometimes called The Hunter) is easy to identify with its classic shape seen in the image above. Betelgeuse (think of the 80s movie Beetlejuice) is a red supergiant star and you can see its reddish-orange tint even with your naked eye.  The three stars that create Orion’s belt point you to the star called Sirius (Yes, I am serious). Sirius is an amazingly beautiful star that is actually a binary star system (two stars orbiting each other).  Sirius is the brightest star in our sky other than our own sun.  If you watch it you will notice that is flashes brilliantly through a variety of colors. This process, called scintillation, is visible with the naked eye as well as through binoculars.

So here’s hoping for good visibility tonight! I hope that you get the chance to get outside and see the beautiful site. As we get into the warmer months, reduced visibility from haze and late day thunderstorms will make such clear viewing of the night sky more difficult.

Enjoy!

March 21, 2012

Spring Has Sprung!

As we woke up this morning to the first full day of spring – many across the county are dealing with an early spring that seems to have gone haywire. From tornado outbreaks in early March, to torrential downpours in the South, and heat waves in the north – March has been one for the record books.  Including a long-lived ridge of high pressure over the Eastern U.S. that has brought numerous record high temperatures to the Eastern and Central U.S. and Canada.

Credit: NASA Earth Observatory image by Jesse Allen, using data from the Level 1 and Atmospheres Active Distribution System (LAADS).

The map above shows land surface temperature anomalies based on data from the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument on the Terra satellite – showing temperatures compared to the average of the same eight day period of March from 2000-2011.  Areas with warmer than average temperatures are shown in red; near-normal temperatures are white; and areas that were cooler than the 2000-2011 base period are blue.

It’s no surprise that Western North Carolina is shown as above normal during this time period as our high temperatures so far this month have been well above average. Only four of the last 20 days in Asheville have been below average for the recorded high temperature! But – it’s hard to find anyone around here complaining about the weather. Our memories of the winters of 2009-2010 and 2010-2011 are still too vivid!

More information on the map can be found here: http://earthobservatory.nasa.gov/IOTD/view.php?id=77465&src=eoa-iotd

March 15, 2012

Return of the Scattered Thunderstorms

For many of us in the mountains – it seems that spring has sprung almost overnight as trees are flowering, birds are singing and allergies have hit full force (cough, cough). Another sure sign of spring. . . . scattered thunderstorms that pop up in the heat of the sun.

The storm pictured above popped up just after noon today close to where  Buncombe, Madison and Haywood Counties meet, west of Asheville . Not an large storm, but radar indicated that the storm did have a hail shaft within it at about 12:30 this afternoon.

These thunderstorms are very typical of spring and summer in the Southeast U.S.  The sun warms the land and the warm air rises in a column creating a cumulus cloud. Cumulus clouds are plentiful this time of year. The puffy white cottony clouds dot the sky on days when there is ample water vapor in the air. Under the right conditions, the moist air continues to rise, the clouds grow tall and a thunderstorm is born. In most cases, these type of storms are not very large and they don’t live for long, especially this early in the year. However, they can produce some locally heavy rain, hail, and lightning  - so they can be dangerous to those who find themselves underneath one. It’s all a sure sign of spring in the mountains.

The image below was taken by NASA’s Aqua satellite this afternoon at around 2:45 pm as it passed over Western North Carolina. You can see the small cottony cumulus clouds over our region as well as the larger, taller and more feathered tops of the thunderstorms that had developed during the early afternoon. Click on the link above for the full image – beautiful!

Sat Image Credit: NASA & Space Science Engineering Center at University of Wisconsin-Madison

Want to know more?  The Institute is hosting a free severe weather workshop at A-B Tech’s Asheville campus on Saturday June 2 with the National Weather Service office in Greenville/Spartanburg.  Mark your calendars!! More details to come.

February 29, 2012

The Word of the Season is  . . . Variability

As we say goodbye to February (YEAH!) and hello to the coming spring – you’ll notice how changes to our environment seem to happen very quickly this time of year.

The sun is growing higher in our sky every day as we head toward the official start of spring on March 20th. Take a look at the image I shot at sunrise on Tuesday morning of this week (2/28). You’re looking due east at the Black Mountains and you can see where the sunrise is occurring now on the horizon compared to where the sunrise occurred at the time of the winter solstice in December.

As we head toward spring, the sun is heating up the Northern Hemisphere again and bringing life back to the mountains. Clear and sunny days can quickly turn cloudy and stormy as North America becomes the battleground for competing warm and cold air masses. Such is the case now as a major storm is spreading snow across the northern states while bringing the chance for severe weather across the central and southeast U.S., including Western North Carolina later today.

So, while we’re beginning to enjoy the signs of the coming spring, remember that because the word of the season is variability – we often see some of the biggest winter storms during the months of March and April.   As they say . . . . “it ain’t over until the fat lady sings” and she’s still backstage, ready to go on at a moment’s notice!

If you’re interested in keeping an eye on the storms, I encourage you to bookmark this website.  It provides a great country-wide view of the Doppler radars that are so critical to providing severe weather information.

February 23, 2012

The Weather Seesaw Returns

Many of us woke up this morning to widespread fog across the French Broad River Valley, thanks to last night’s rain that caused the layer of air at ground-level to become saturated – producing a cloud on the ground – or fog. Looks like we may see similar conditions on Friday morning because we may see some more storms again tonight that may lead to some fog early tomorrow morning – especially in protected valleys.

Enjoying the great, mild weather today?  I encourage you to do so because winter will make itself known again tomorrow as a strong cold front will likely produce strong, gusty winds during the day as it brings some much colder air into Western North Carolina. The National Weather Service has already issued a Wind Advisory for our region starting at 9:00 a.m. tomorrow as a heads-up for the possibility of downed trees and difficulty in driving large vehicles.  Keep in mind that fires can easily get out of hand in high winds, too. So, no burning tomorrow.

Typical of the systems that we’ve seen this winter, we’ll probably see some short-lived rain and maybe a few snow flurries with the cold front, all helping to keep the western part of the state in much better shape than central and eastern sections who continue to see below average rainfall. 

Interested in seeing how we’re faring compared to the rest of the state? The State Climate Office of NC has just released its annual climate summary containing an overview of the extreme weather observed across North Carolina in 2011, including information on the April 16th tornado outbreak, the summer heat and drought, and Hurricane Irene's landfall in late August. All this and more is online here.

February 16, 2012

Where is Winter?

Snowflakes were flying earlier this week, as Valentine’s Day started off white at the higher elevations.  This image of Max Patch in western Madison County shows the short-lived snow.  So – what has happened to this winter? Why has it been so different than the last two years?

Following the harsh winters that Western North Carolina endured during the last two years, we were all waiting with some dread to see how the winter of 2011-2012 would present itself.  I don’t know about you, but I’ve really enjoyed the ability to work in the yard this winter - the same yard that was covered in 3 feet of snow during the same period for the last two years!

Whether you’re enjoying the break – or are wishing for a good ol’ winter storm – we can all look to the polar vortex for hints about what has contributed to the warmer than usual winter across much of the lower 48 states. The polar vortex is a band of winds that blow counterclockwise, circling the Arctic.  During some years, that band of winds is very strong and acts as a dam that keeps much of the cold air locked up over the polar regions, and out of the lower 48. So far, that’s been the situation for much of this winter.

Meteorologists track the polar vortex by watching two related oscillations in the Northern Hemisphere, the North Atlantic Oscillation (NAO) and the Arctic Oscillation (AO). Similar in some ways to El Nino and La Nina, these regular oscillations impact short-term climate, but their influence is usually limited to the Northern Hemisphere. If you are interested in learning more about these oscillations and their impact on North Carolina, the State Climate Office of North Carolina has an excellent write-up here.

For much of this winter, the NAO and AO indices have both been very “positive”.  In this state, the polar vortex has kept much of the cold air locked up over the arctic region resulting in less snow and fewer outbreaks of really cold air across the contiguous U.S.  The image below shows the NAO and AO indices for the month of December for each of the last sixty years. You’ll notice that December of 2011 was strongly positive for both the NAO and the AO, but that the previous 2 winters were very strongly negative for both of the indices.  Do you remember a particularly bad winter over the last 60 years? Take a look and see is both the NAO and the AO were both negative. The winters of much of the 1960s are a good example.

Graph by Hunter Allen (NOAA) and Robert Simmon (NASA) based on data from NOAA’s National Weather Service Climate Prediction Center.

Keep in mind – we have a long way to go until spring, and some our most impressive winter storms can still occur even into April.

In the meantime, Western North Carolina continues to enjoy above average temperatures and precipitation.  However,  it looks like we may see a little snow, especially in the mountains this weekend. Not too bad - for the dead of winter.

 February 1, 2012

W is for Water . . . not Winter (apparently)

As we head into February, Western North Carolina continues to see plentiful rain as a steady stream of weather systems spread rainfall across the southern plains and into our area. 

The image below shows the rainfall totals for January across the SE U.S. (The scale on the right is in inches.)

Asheville has seen its fair share of rain over the last several months.  The monthly total for January at the AVL airport was 3.85”.  That’s 0.18” above the average rainfall for January. And, we came into 2012 with some above average rainfall accumulations in November (1.67” above average) and December (1.52” above average).

With rain in the forecast for much of the weekend, it looks like we’ll keep adding to the totals in the near-term. 

These images were generated using the National Weather Service’s radar and rain gauge data here.

January 26, 2012

Our Planet – A Unique View of a Truly Unique Place!

Most of us have seen the famous “Blue Marble” picture that was taken on December 7, 1972 by the astronauts on Apollo 17 as they were headed to the moon.  The famous image, below, was taken with a hand-held camera just over 5 hours after launch, as the last manned lunar mission was about 2800 miles from the Earth.

Credit: NASA

NASA has now released an amazing new view of our planet. One that highlights the advances that we’ve made in observing the Earth’s weather and climate from the satellites that orbit our planet.

Credit: NASA

Click on the image above for a high-res version (16.4 MB)

The image above is not a single image taken with a camera, but a series of images taken 512 miles above the planet by the newest Earth-observing satellite launched by NASA, the Suomi National Polar-orbiting Partnership (NPP).

Launched from Vandenberg Air Force Base in California on October 28, 2011, the satellite began making its first measurements in November as scientists tested the instruments. The image above was produced on January 4th of this year (an amazingly clear winter day across North America) by the Visible Infrared Imaging Radiometer Suite (VIIRS), one of the 5 scientific instruments on board.You may remember that on that day Western North Carolina had just seen snow at the higher elevations. You can see the cloud cover with that system moving toward the NE U.S.in the image above. (See the January 5th Fun Facts e-mail for a view of the snow from NASA’s Terra satellite.)

As a polar-orbiting satellite, Suomi NPP rises in the south and sets in the north on the daylight side of the planet. As the Earth rotates below it, the satellite circles from south to north 512 miles overhead imaging a 1,900 mile wide swath. This allows the satellite to cover the surface of the globe in a day. But the satellite’s orbit is also sun-synchronous, meaning that it passes over the equator at the same local time on the ground. This maintains the angle between the sun and the Earth – so all images have similar lighting producing a consistent and well lit view across the whole globe.

Suomi NPP does so much more than take beautiful images. It is the first satellite designed to collect data to improve short-term weather forecasts and to increase our understanding of long-term climate by measuring key climate variables.  It is a bridge between NASA’s Earth Observing System satellites and the next generation of weather and climate observing satellites called the Joint Polar Satellite System, a National Oceanic and Atmospheric Administration (NOAA) program.  Data from Suomi NPP will come to NOAA’s National Climatic Data Center in Asheville.

To learn more about Suomi NPP click here.

To learn more about how NASA constructs images of the Earth - click here.

January 19, 2012

Where the Trees Are . . . and Aren't

Credit: NASA Earth Observatory map by Robert Simmon, based on multiple data sets compiled and analyzed by the Woods Hole Research Center

For the first time ever, researchers now have a detailed view of the forests across the lower 48 states. Taking 6 years to complete, the National Biomass and Carbon Dataset project mapped our nation’s forests at the highest resolution ever (30 meters), providing baseline information about tree height, forest structure and carbon storage capability in the year 2000.

It’s believed that as much as 45 percent of the carbon stored on land is tied up in trees. Western North Carolina’s unique climate has produced amazing biodiversity across our region and our important role in the Earth’s carbon cycle is evident in the dark green colors on the national map above. The map depicts the concentration of biomass— a measure of the amount of organic carbon—stored in the trunks, limbs, and leaves of trees. The darkest greens reveal the areas with the densest, tallest, and most robust forest growth.  

And while it’s interesting to see the important role that our forests play in the role of carbon storage - it’s the details of the new maps that will leave you stunned.

The image below is an up-close look at Western North Carolina/Eastern Tennessee taken from the national map. Heavily forested areas are dark green, lakes are light blue, and areas with less trees are lighter in color.  Can you make out the major population centers in the region?  If you look carefully – you can even see the corridors formed by major roadways such as I-40 through Buncombe County and Highway 19 through Madison and Yancey Counties.

Credit: NASA Earth Observatory map by Robert Simmon, based on multiple data sets compiled and analyzed by the Woods Hole Research Center

I’ve labeled some of the major points of interest in the image below to help you find your way around.

Credit: NASA Earth Observatory map by Robert Simmon, based on multiple data sets compiled and analyzed by the Woods Hole Research Center with annotation by Pamela McCown

You can find NASA’s story on the project here.

January 11, 2012

Angry Skies

The clouds thickened over Western North Carolina this morning (Wed. 1/11) as the latests storm system brought rain into the region. The image above was taken in Madison County as the rain was moving in. We’ll continue to see showers, and maybe even a few isolated thunderstorms, through the rest of the day and into tonight.   The next weather maker is right on its heels and we’ll feel its impact by late tomorrow.

A heads-up as the mild temperatures we’ve been enjoying this week will come to an end late tomorrow as a cold front sweeps into the region. The cold air will help produce snow showers across the area, with accumulations most likely in the higher elevations tomorrow night.

The cold front will also bring gusty winds that could increase the risk of falling trees, especially with our soils so wet from today’s rain.

Wet soils also increase the risk of ice on roadways tomorrow night and into Friday as the runoff and temperatures below freezing will combine to create problems with black ice on roads. So, be careful.

NASA’s Terra satellite caught the 2 weather systems as the satellite passed over the Central and SE U.S. at around noon today. You can see the area of low pressure that I labeled as “1” and its movement to the NE.  The cold air (labeled “2”) is moving toward the SE and is expected to arrive in Western North Carolina late in the day tomorrow.

Image Credit: NASA and the  Space Science and Engineering Center (SSEC) at the University of Wisconsin-Madison.

You can always find the latest forecasts and radar images for Western North Carolina from the National Weather Service Forecast office in Greenville-Spartanburg.

January 5, 2012

Clear Skies for This Evening’s International Space Station Pass

Sat Image Credit: NASA & Space Science Engineering Center at University of Wisconsin-Madison

The image above was taken today (1/5/2012) by the Terra satellite, part of NASA’s Earth Observing System. It shows that the skies are so clear over Western North Carolina that we can still see the areas of snow left from the snow event earlier this week.

These clear skies should make for excellent viewing this evening of the International Space Station as it makes a pass over our region beginning at 6:33 pm.  Look to the WNW. You’re looking for a bright light, similar to Venus, that is visibly moving toward the south.  Traveling at a speed of over 17,000 mph, the ISS will be visible for over 6 minutes as it crosses relatively low on the horizon – at about 30°.

Grab a pair of binoculars, if you’ve got them, and watch this engineering marvel as it orbits the Earth at an altitude of over 230 miles.

You’ll find more information about spotting the International Space Station here.

December 21, 2011

Bring On The Light!

Are you tired of the long hours of darkness?  If so – rejoice as the powers of light are about to overcome . . . the dark side (insert “Darth Vader’s Theme” music here)!

The December (winter) solstice occurs at 12:30 AM EST tomorrow morning marking the beginning of astronomical winter in the northern hemisphere, and the return of more hours of daylight.

For many of us – the winter solstice passes almost unnoticed thanks to modern conveniences like electricity and cars with headlights. But these are relatively new technologies that allow us to function through the long hours of darkness that occur this time of the year. Past generations were much more aware of the changing seasons because the lack of natural light had a significant impact on one’s ability to be productive. As a result, the winter solstice was a time of great celebration.

Beginning tomorrow– we will gain precious daylight each day as the Earth’s northern hemisphere begins to pick up more sunlight on our yearly trek around the sun. These changes occur because our planet is tilted 23.5 ° in relation to the sun. And, at the winter solstice in the northern hemisphere, the Earth’s axis is tilted at its largest angle away from the sun as shown in the illustration below. 

Credit: Timeanddate.com                              Note: Not to scale

Today and tomorrow (12/21 and 12/22) are the days with the shortest daylight hours of 2011 here in Western North Carolina. Each day having just under 9 hours and 45 minutes of daylight in Asheville. Compare that to the 14 hours and 34 minutes of daylight that Asheville sees at the summer solstice in June, and you can understand why our ancestors would celebrate the return of the sun in late December with festivals that would last for days, even weeks.

I encourage you to take time over the next couple of days to notice where the sunrise and sunset occurs on the horizon.  This is as far south as the sun will appear to us  - and the difference between where the sun rises and sets in December, and where it rises and sets well to the north in June, is truly amazing.

Click on the image below to get an interesting perspective on how the sun’s light changes on the Earth through the year.  This movie was produced from a series of images from the European Organization for the Exploitation of Meteorological Satellites (EUMETSAT).

Credit: NASA images and animation using data ©2010 EUMETSAT

December 13, 2011

Meteor Shower Tonight!

Mid-December brings one of the most unique meteor showers that we get to see throughout the year, the Geminid Meteor Shower. And, although viewing conditions won’t be perfect for viewing in Western North Carolina, the mild conditions may make it worth the effort.

We’ll likely see some cloud cover with the bright Waning Gibbous moon tonight (just past full at 90.5%). We may also see the development of some fog in the valleys overnight, but if you venture outside after 10:00 tonight, set out a blanket, make yourself comfortable and give your eyes time to adjust to the darkness, you may get a glimpse of a few meteors. Point your feet toward the East, and look toward the constellation Gemini (see the sky map below). Viewing is always best if you can get to an area without city lights, but we’re expecting mostly cloudy skies tonight. So, a special trip away from any lights may not be worth the effort if the clouds do set in.

Most meteor showers are produced as the Earth crosses the debris path left by a comet. However, the Geminid Shower is unique because it’s created from the dusty debris left by a near-Earth asteroid named 3200 Phaethon.

 Credit: Dr. Tony Phillips, NASA Science News

For more detailed information on the Geminid Meteor Shower from NASA Science News, click here.

December 8, 2011

Snow – From Two Different Perspectives

Last night’s snowfall blanketed the higher elevations with a couple inches of snow bringing beautiful views this morning, both on the ground, and from space!

The image above was taken by the GOES-13 satellite that hovers about 22,300 miles above the Earth to provide critical weather observations over the Eastern U.S.  Clear skies at sunrise made it possible to see the white areas of snow along the Southern Appalachian Mountains. If you look closely, you can also see the snow on the mountains of NE Buncombe County.  

The image below shows the ground truth. Beautiful snow – but also areas of rime icing on the trees.

Rime icing occurs when super-cooled (below freezing) water droplets collect and freeze on objects. This happens when low clouds and/or fog form in sub-freezing conditions and it occurs quite often during the cold months here in Western North Carolina. Up close, rime ice crystals are uniquely beautiful because they grow INTO the wind, making delicate spikes.

November 30, 2011

First Accumulating Snowfall of the Season. From this . . .

. . . to this in 3 hours.

Early yesterday afternoon (11/29), snow flurries started at the higher elevations in Madison County and it wasn’t long before a dusting turned into the first accumulating snowfall of the season.  The first image above was taken around 1:00 yesterday afternoon. Three hours later, the same trees resembled the flocked Christmas trees I remember seeing at the tree lots of my youth. (I grew up in Houston, TX - I had no idea what a real snow-covered tree looked like!)

There were still snow flurries in the mountains this morning. But by this afternoon, the snowfall has come to an end and the clouds are slowly dissipating to the north of Asheville as the cold air continues to spill into the valley through the gap formed by the French Broad River.

Unofficially, we saw between 2” and 2 ½ “ at 4000 ft.  If you’d like to see the reports from around the region, you can find the National Weather Service Spotter Reports here.

November 21, 2011

Doing the Wave . . .

You may have noticed a significant change in our skies yesterday afternoon as fair skies turned cloudy. These clouds moved in from the west late in the day ahead of the system that brought showers overnight and more significant rain into the region this afternoon.

I noticed an interesting feature to the clouds . . . waves. The waves are caused by the interaction of the air with the complex terrain in the mountains and they occur fairly regularly, especially in the fall, winter and early spring as storm systems approach from the west. The clouds in the picture are called Altostratus Undulates.

Meteorologists classify clouds using three main criteria:

-Height of the cloud base

-Shape

-Whether or not the cloud is producing precipitation

 In this case, the clouds were at mid-level (6,500 – 20,000 ft).So, they are given the name Alto –meaning mid. Their shape is like that of a sheet or blanket. So, they are called Stratus – meaning layer.  And, you can recognize the word undulate, meaning wavy. (Scientists love to use Latin to classify things – even clouds!)

November 9, 2011

Planets at Sunset

It’s easy to forget that we live on a rock that is hurling through space in an orbit around our star – but occasionally, we can see reminders of that fact when our fellow planets are beautifully displayed in the sky over our mountains.

This is a great month for sky watchers. The planets are putting on a show in our evening skies and our atmosphere is typically clearer than it is during the summer months thanks to frequent frontal passages that help bring in cleaner and drier air.

The image above was taken last night (Tues 11/9/2011) as Venus and Mercury (along with a few cirrus clouds) were visible to the southwest after sunset. Clouds have increased today (Wed) ahead of an approaching cold front that will hamper viewing tonight, but clearer skies are expected later in the week, and it will be easy to spot Venus as the bright “star” on the southwest horizon after sunset.   Mercury is there too, to the lower left of Venus, but you may need to look through binoculars to really see it well.

Have you been wondering what that brilliant evening star in the East is?  It’s not a star at all, it’s Jupiter!

Looking to the East just after last night’s sunset, Jupiter was a bright beacon just below the moon.  The planet is easy to spot because it is so bright and it remains visible all night as it climbs high in our sky and eventually sets in the west in the early morning hours. Jupiter will be easy to see all month. So, pull out your binoculars or telescope and you’ll even be able to see some of Jupiter’s moons - well worth the effort!

October 27, 2011

Sundogs

Just before sunset last night – the ice crystals in the cirrus clouds that you can see in the picture created an optical phenomena known as a sundog.  Sundogs, also called parhelia (Greek, meaning “beside the sun”) appear to follow the sun as it moves in the sky -  that is why they are called sundogs.

A little background – cirrus clouds are high, thin, nearly transparent wispy clouds that are made of ice crystals.  Sundogs occur when the ice crystals that form the cirrus clouds are all aligned vertically so that they refract the sunlight and produce bright spots of light concentrated on either side of the sun.  In many cases there are two spots, one on each side of the sun. Last night, I was only able to see one sundog that appeared to the south of the sun about 15 minutes before sunset when I took the picture.

Weather lore sayings warn that sundogs can alert us to a coming change to the weather.  In this particular case, the weather lore will prove to be correct.  Last night’s cirrus clouds were the first sign of increasing moisture ahead of the clouds, rain and colder air that are moving into Western North Carolina tonight and tomorrow (Thursday and Friday, 10/27 & 10/28).

October 18, 2011

So soon to say goodbye . . . Brace yourself!

If you have a favorite color spot – make a point to see it today before winter-like conditions move into the area beginning tomorrow!

A cold front will move into Western North Carolina early tomorrow bringing much colder air, rain and gusty winds that will likely bring many of our fall colors crashing to the ground. Tomorrow (Wed) will seem dramatically different than the beautifully warm days we’ve enjoyed recently. So, be prepared.  Scattered showers and falling temperatures throughout the day will combine with gusty winds tomorrow night into Thursday and that’s not good news for those of us who enjoy the color of fall leaves.

There’s also a decent chance for snow for folks above 3500 ft. The Great Smoky Mountain National Park will likely see snow beginning during the day tomorrow and that area of snow will move toward the east into Haywood and Madison Counties by sunset tomorrow with accumulation possible through Thursday, especially at locations over 4000 ft.

So, enjoy these last hours of beautiful fall weather and be prepared for a taste of winter . . .  all too soon if you ask me!

 October 12, 2011

Foggy Start to a Beautiful Day!

This morning started with fog over many of the valleys in Western North Carolina, as you can see in the image above of Mount Pisgah taken across the layer of fog that settled into the French Broad River Valley overnight.

With mostly clear skies over the region, the morning fog shows up well on visible satellite images.  Click the image below for a loop of images taken by the

Geostationary Operational Environmental Satellite-East (GOES-E).  Note the arrow pointing to Buncombe County in the first frame of the animation to help you get your bearings. You can see the fog disappear as the morning progresses.

As a geostationary satellite, GOES-E travels at the same speed as  the Earth’s rotation, allowing it to hover over the same place on the planet at an altitude of about 22,300 miles above the Earth. The U.S. normally operates two meteorological satellites in geostationary orbit, GOES-E and GOES-W. These satellites provide many of the images that we use to track weather systems, including the satellite images you see during weathercasts on the local news.

For more information on the GOES satellites, click here. Interested in more satellite images? You’ll find one of my favorite resources here.

October 6, 2011

Smoke on the Water . . .

Well, OK – it’s really fog - but I could still hear the Deep Purple song in my head this morning as the French Broad River is clearly visible snaking through the valley under its thin veil of fog just before sunrise this morning.

Light winds, clear skies and longer nights are the perfect recipe for the development of river fog. The relatively warm water of the river gives up some of its moisture to the cool air just above the river and the air becomes saturated, creating a layer of fog. Fog develops when the air temperature drops to the dew point and the water vapor in the air condenses into water droplets.  Once the sun rises, the air quickly heats up (so it’s no longer saturated) and the fog vanishes.

For those of you waiting for the rest of the phrase . . .

 . . . And Fire in the Sky

Turning to the east just seconds later - about 60 seconds before the sun rose over the Black Mountains.

 September 29, 2011

Too Cool to Not Share!!

The astronauts on the International Space Station (ISS) captured an amazing movie of the “southern lights” while passing over the Indian Ocean on September 17th.  Click on the image above to start the movie.You can see the solar panels and other sections of the ISS in the movie as the station passes over the Southern Hemisphere.

 The “southern lights” (aurora australis) are the South Pole’s version of the aurora borealis, the “northern lights”. This display was brought on by an explosion of hot, ionized gas from the Sun—a coronal mass ejection—that left the Sun on September 14, 2011.

The beautiful ribbons of light are caused by fast-moving electrons that collide with Earth’s upper atmosphere, transferring their energy to oxygen and nitrogen molecules and making them chemically “excited.” As the gases return to their normal state, they emit photons, small bursts of energy in the form of light. The color of light reflects the type of molecules releasing it; oxygen molecules and atoms tend to glow green, white or red, while nitrogen tends to be blue or purple. These lights originate at altitudes of 60 to 250 miles in our atmosphere

For more information – visit NASA’s Earth Observatory website here.

September 22, 2011 

The Season of Spectacular Change!

At 5:05 a.m. (EDT) Friday morning, those of us in the Northern Hemisphere pass into what is arguably the most wondrous of all seasons . . . autumn.

We’ve already seen a shift to cooler conditions as the Sun is no longer at its highest point in our sky and you may have noticed how the hours of daylight are getting shorter as well. At noon on June 21st, the longest day of this year, the Sun was at its highest elevation angle above Asheville at 77.9° and we enjoyed 14 hours and 34 minutes of daylight. By September 23rd, the Sun’s angle at noon has already decreased to 54.3° and the daylight hours have decreased to 12 hours and 7 minutes.

Changes happen quickly this time of the year.  The leaves seem to change overnight and the squirrels are so busy that they forget to look both ways as they cross the road and many of them meet their fate.

Enjoy these days as they too will pass quickly. Our orbit around the sun will soon bring the shortest days in the Northern Hemisphere when we will have only 9 hours and 45 minutes of daylight on the first day of winter in December.

 For more information:  http://www.timeanddate.com/worldclock/astronomy.html?n=745

September 15, 2011

Looking Into the Face of Evil

If you suffer from allergies, late summer is a particularly bad time because it’s when the ragweed plants in our area release their pollen . . .and spread misery.  There are numerous species of ragweed, some are short, but the Giant Ragweed plant I took this picture of yesterday in Madison County is over 13’ tall! In all, there are 21 species of ragweed in the U.S. A single plant lives only one season, but can produce up to 1 billion grains of pollen.

The individual grains of pollen (shown magnified in the inset picture) travel long distances on the wind, thanks to tiny air bladders that help them to be buoyant.(You can see the bladder as the light circle on the outer edge of some of the grains.)

Weather plays an important role in pollen production and dispersion.  The plants typically release the pollen in the early morning, just after sunrise when the relative humidity is fairly high. The moisture helps the air bladder remain flexible so the grains can catch the breeze and travel long distances. Ragweed pollen has been measured in the air 400 miles out to sea and 2 miles up in the atmosphere!  Rain and temperatures below 50°F help to slow the release and rain also helps to scour some of the pollen from the air as it falls. So, those of us suffering may get some temporary relief with the approaching cold front.

Additional Info:

Avoid Nasal Allergies.com http://www.avoid-nasal-allergies.com/index.html

Asthma and Allergy Foundation of America http://www.aafa.org/display.cfm?id=9&sub=19&cont=267

September 7, 2011

How Much Rain Did You Get?

The image above shows the wide variation of rainfall that occurred across the region over the Labor Day weekend as a result of the remnants of Tropical Storm Lee. While it may look like someone spilled something on the map, the legend on the right side of the image (units are in inches) will help to make sense of the colors.  Just like the radar images you see on the evening news, the brighter oranges and reds indicate the heavier rainfall,as seen just south of Boone where there were reports of 6”- 8” of rain.   The total for the event in Asheville, recorded at the airport, was 1.82” of rain.

The image below shows the impact of the rain to date over the Eastern U.S. – where it continues to rain, even into today (Wed 9/7/2011).

 

These images were generated using the National Weather Service’s radar and rain gauge data here.

August 31, 2011

The Layer We Live In

The Earth’s atmosphere has many layers, each playing their part to make this planet an oasis for life. You’ve heard of the Ozone Layer – located in the stratosphere – it helps to absorb dangerous ultraviolet radiation from the Sun. The troposphere is the lowest layer of atmosphere and is where almost all weather occurs.  The lowest part of the troposphere - where we live  - is called the  Planetary Boundary Layer or PBL.  This layer, usually less than 1 mile deep is where our atmosphere is in contact with the planet. When conditions are right, you can see the PBL from higher elevations, as was the case yesterday evening (8/30/2011). The recent stable weather pattern over Western North Carolina has not allowed the air in the PBL to mix with the free atmosphere above it.  As a result, tiny particles of smoke, pollen, dust, etc. have collected in the PBL causing the hazy conditions that we sometimes experience during the summer. In the image taken yesterday evening, the PBL is plainly visible hanging over the valley. Good news is that we are expecting a change to the weather pattern during the upcoming holiday weekend that may bring a chance of rain and help to clear the particulates from the air.   

August 24, 2011

Irene Is Cause for Concern as Major Hurricane Takes Aim on NC and the Highly Populated East Coast

Many of us in Western North Carolina know that hurricanes are not something to dismiss simply because we’re in the mountains and hundreds of miles from the coast.  The storms of 2004 (Charley, Frances, Ivan) left their mark on the mountains and our communities with flooding rains, landslides, and high winds.  On its current projected path, Hurricane Irene does not pose an immediate threat to the mountains - we may see gusty winds and a shield of high clouds from the storm. However, it does pose a threat to much of the state and will threaten millions as is moves up the coast into the Mid-Atlantic and New England. Those with property and/or family along the coast should stay informed and have plans for contacting those in the path if the worst should be realized. Irene reached Category 3 status this morning and may become a Category 4 hurricane on Thursday.

 Important points to remember:

• Do not focus only on the path of the storm and its projected landfall.  Irene is a large storm and it will have a significant impact over a very large area.
• If you own property along the coast, do NOT plan on “riding out the storm” along the coast. All indications are that this will be a historic hurricane with the potential to do really bad things to property, life, communication systems and the structure of the coast itself.
• Stay informed!  Here are my favorite sites for information related to tropical systems:

• National Hurricane Center :  http://www.nhc.noaa.gov/index.shtml#IRENE  (lots of maps so you can see what the experts think the storm will do)
• NASA: http://www.nasa.gov/mission_pages/hurricanes/archives/2011/h2011_Irene.html  (cool satellite images and visuals)

Image and video from NASA

 Click on the image to see a video of Irene as it grows from a disorganized system into a Cat 3 Hurricane with a well-defined eye. You may notice that you can see the change from day to night sweep westward across the land as the video progresses.

 August 23, 2011

Morning Fog Alongthe French Broad River Valley

The cooler and drier air we’re enjoying across Western North Carolina on this late summer day set the stage for fog this morning across the region, especially along the rivers.  This image, taken at 7:08 AM on 08/23/2011 shows the fog in the French Broad River Valley as seen from Madison County looking south toward Asheville.

The French Broad is not only a focus of recreation for locals and tourists alike, it also impacts the weather and climate of the area by allowing air masses and storms to move from Tennessee into North Carolina through the valley formed by the river. 

Some say that the French Broad River is the third oldest river on Earth and it is one of a few rivers in the U.S. that flows to the north! (http://www.ashevillenc.com/area_info/french_broad_river )