Friday, January 29, 2010

Parts of East Texas Could See Ice.



As we were hinting to yesterday, forecast models are having a hard time handling this shallow arctic air mass moving into East Texas. Temperatures already are around five degrees colder than these models were indicating and if this trend continues, a few areas north of I-20 could see some freezing rain later this afternoon.

As an area of low pressure moves to our south, northeast winds are bringing much colder air into the area from the Ozarks this morning. This is allowing middle 30s to set a foundation across the northeastern corner of East Texas. Rain will continue to develop to are southwest throughout the day as temperatures continue to drop towards the freezing point. Ground temperatures across East Texas are well above freezing so we are not anticipating a significant icing event. However, temperatures in a few areas will drop down to the freezing pint before the rain moves out, so ice could begin to accumulate on elevated surfaces such as trees and power lines as well as bridges and over passes later today. The best chances of this occurring will be from a Sulphur Springs to Pittsburg to Jefferson and points north and east.



We are still watching an upper level disturbance that will move towards the Red River Valley this evening. Moisture wrapping around the back edge of this system could bring a few snow flurries or freezing drizzle to the northern half of East Texas. Right now we are not anticipating much in the way of travel problems however; please use caution while driving over bridges and overpasses this evening and overnight tonight. Stay tuned to your East Texas News Leader for the latest.

Thursday, January 28, 2010

Line of Severe Storms Continues



Line of storms continues. Good news is the storms are moving faster east than the low level jet. It is the low level jet that is fueling these storms with the lack of instability. Once these storms move off the jet axis, they should begin to weaken. This should happen just as these storms approach the Tyler area. Western counties could still see a severe wind gust or two. i plan on meeting these storms as they enter Kaufman CO. Watch for pictures later.

Wind Damage Reported With Storms



Wind damage reported in Cross Plains at the Hwy 36 motel. Roof is damaged and power lines down. Damage caused by a possible tornado. If this line holds together it will be in our western counties around 5:30PM. Doppler radar shows sings of rotation all along this line with winds up to 60 mph all along this line.

Look at the Temperature Difference



Temperatures range from 19 in Amarillo and Dalhart to 77 in Del Rio at 1PM. Severe storms are forming in central TX with a tornado warning out for Eastland CO. Strong gusty winds could occur across East Texas if this line holds together. Flash flood warning are also in effect with this line but as the line speeds up, flooding concerns will decrease.

On the cold side of the storm. I-40 around Amarillo is closed. Up to 6" of snow has fallen in the Panhandle with drifts up to 2 feet. Visibilities in heavy snow are under 100 yards. This is going to be a historic storm across parts of the Southern Plains. If you plan to travel across Oklahoma or the Texas Panhandle, cancel don't. Conditions are life threatening in these areas.

1"-2" of Rain for East Texas, Major Ice Storm North.



A strong winter storm is developing across northwest Texas today and will spread a major ice and snow storm to our north. For East Texas this system will bring a round of very heavy rain with one to two inches likely for most of the area with a few localized spots receiving up to three inches. We are not anticipating any flooding problems at this time however, the will be ponding of water on roadways and some areas could see localized flooding during the heaviest rainfall tonight.

The big question on everyone’s mind is will we see any ice or snow with this system. As stated above, there will be a major winter storm to our north. The amount of snow and ice that falls to our north will actually have an impact on our forecast and could cause some areas to see a sleet and snow mixture before the precipitation moves out. The best chance of this occurring is from Terrell to Quitman to Mt. Pleasant and points north and west. It also still appears the lowest levels of the atmosphere will remain saturated through early Saturday morning. This could produce a period of freezing drizzle from 10PM Friday through about 3AM Saturday. This drizzle would be very light but could cause a few problems on elevated surfaces.

I will end with this little tid-bit of information. The last system we had like this in December that produced a band of snow to our north caused temperatures to drop much quicker than our forecast models indicated. This is where the human element to forecasting is really important. Temperatures were around 5 degrees colder than forecast and hit the freezing mark much. This was all due to a band of ice and snow to our north. So I do feel we will hit the freezing mark a little earlier tomorrow evening than the forecast models area showing now. This forecast will likely change over the next 24 hours as we get accumulating snow to our north so stay tuned to your East Texas News Leader for the latest.

Wednesday, January 27, 2010

Heavy Rain Followed by Possible Ice



Very heavy rain is expected across East Texas over the next 36 hours. A strong winter storm is developing over the southwest and will move across the State tomorrow. The northern end of this storm, from the Red River north, will produce a major winter storm with Freezing rain, sleet, and snow. Severe weather is also possible with this system across the Gulf Coast.

For East Texas it looks like we will mainly see a heavy rain event. The graphic above shows the forecast amount of precipitation 6AM Thursday to 6AM Friday. Notice most of East Texas will have between 1.5" and 2" of rain. The big question for us is will the cold air make it in time for a winter weather event? Right now the answer is no however, there are a few complications to this forecast.



The image above is a forecast Meteogram for Tyler from the 0Z run of the GFS forecast model. The red line is the air temperature with the blue lines indicating wind chill temperatures, think blue from sustained wind and thin blue from wind gusts. Very heavy rain is indicated by the thick green bars towards the right of the graph, time goes from right to left, backwards from what you might expect. Notice the temperatures plunge as the rain moves out. However, this is showing a burst of wet snow, the thick blue bar, Friday afternoon. Now I am not buying into this right now but it does show there is a chance of a few flurries. As the temperatures bottom out Friday night into Saturday morning, notice the precipitation is still in the area, very shallow red, orange, and blue bars. This would be a prolonged period of light freezing drizzle, about 0.02" total amount of precipitation. This would not be a crippling ice storm by any means however, with temperatures in the 20s, we would see a light glaze on area roads and elevated objects. So we will have to watch this very closely.


Now the colors on the Meteogram have the following meaning, green=rain, blue=snow, red=freezing rain, orange=sleet. So it looks as though a lot of that light precip would be flurries and not cause a big problem. However, when you look at the atmospheric sounding, its paints a much different picture. In order to get ice crystals to grow, the temperature needs to be around -10°C or 14°F. You can see in the sounding above the temperature is below freezing the entire column of the atmosphere however, in the saturated area, where precipitation forms, the temperature never reaches that critical level. So this would produce drizzle across the area, liquid precip, that would freeze on contact. Let me say that forecast models have a very hard time handling shallow Arctic air, like this. We could see the low levels of the atmosphere dry out much quicker than indicated just giving dry, cold condition. But if what the models are hinting does occur, we could see freezing drizzle for the northern half of East Texas for as much as 12 hours, and this would cause many travel troubles.

Tuesday, January 26, 2010

10th Tornado Confirmed Near Whitehouse


A small tornado track was found near Whitehouse on Joye LN (CR 2192). This brings the total tornado count for East Texas to 10.

Hopkins County; 2 EF-0 tornadoes
Van Zandt County; 1 EF-2 tornado (earlier thought to be 2 seperate tornadoes)
Henderson County; An EF-1 and an EF-2 tornado
Smith County; An EF-0 and an EF-1 tornado
Harrison COunty; an EF-1 and an EF-3 tornado
Sabine County; and EF-1 tornado

Monday, January 25, 2010

A Look Back at Wednesday's Tornadoes

Funnel Cloud in Flint

It was a very busy night Wednesday evening as severe weather struck East Texas producing at least 9 tornadoes and numerous reports of large hail. I thought I would take you through the event by looking at each storm that produced a tornado and show you what we see on radar to determine if a storm could produce a tornado.

The Waskom Tornado

The 1st tornado we will look at is the Waskom Tornado. The storm that produced this tornado developed over southeastern Smith CO in the early afternoon and produced up to Golfball size hail near Arp. The three images below are of the velocity data, showing you the tornado circulation, the reflectivity, and the volumetric data. As the storm crossed the interstate and produced most of its damage, it looks as though the radar is picking up a debris ball, an area of enhanced reflectivity on the tip of the hook. The radar beam was hitting this part of the storm at 950’ so it is very possible we are seeing rooftops and trees swirling around this storm. In the volumetric scan you see a large area of deep purple indicating this storm had intense updrafts able to produce large hail and ultimately, a ¾ mile wide EF-3 tornado.







Below is from the National Weather Service :

THE NATIONAL WEATHER SERVICE COMPLETED A DAMAGE SURVEY IN HARRISON
COUNTY TEXAS...AND CADDO PARISH LOUISIANA. AN EF3 TORNADO FIRST
TOUCHED DOWN NEAR WASKOM...TEXAS IN A WOODED AREA WEST OF IRELAND
WILLIAMS ROAD. THE TORNADO QUICKLY INTENSIFIED AS IT APPROACHED
INTERSTATE 20 NEAR MILE MARKER 628 WHERE 2 BUSINESSES WERE DESTROYED
ON BOTH THE SOUTH AND NORTH SERVICES ROADS. ONE OF THE BUSINESSES
WAS A METAL BUILDING AND THE OTHER WAS A MOBILE HOME. ONE HOME WAS
COMPLETELY DESTROYED WITH ONLY A FEW INTERIOR WALLS REMAINING. A
SECOND HOME SUSTAINED MAJOR DAMAGE TO THE ROOF AND CARPORT. DEBRIS
WAS SCATTERED ACROSS INTERSTATE 20 AND HWY 80. SEVERAL OTHER HOMES
WERE DAMAGED FURTHER EAST ALONG BOTH SIDES OF THE SERVICE ROAD. MANY
TREES WERE SNAPPED AND UPROOTED IN THE AREA...SOME WERE SNAPPED DOWN
CLOSE TO THE BASE. THE TORNADO CONTINUED NORTHEAST...CROSSING
BELLVIEW ROAD INTO JONESVILLE...TEXAS WHERE A GROCERY STORE ROOF WAS
PEELED BACK AND WALLS WERE BLOWN OUT OF A LARGE WAREHOUSE. THE
TORNADO ALSO DAMAGED SOME METAL BUILDINGS NORTH OF JONESVILLE ALONG
FM 134. THE TORNADO TRACKED EAST ACROSS A WOODED AREA...SNAPPING AND
UPROOTING TREES CROSSING FM 9...AND THEN HEADED EAST INTO CADDO PARISH
IN LOUISIANA. A WEAKENED TORNADO CONTINUED EAST...CROSSING GREENWOOD
MOORINGSPORT ROAD WHERE SEVERAL TREES WERE UPROOTED AND CONTINUED
EAST OVER PORTIONS OF WESTERN CROSS LAKE BEFORE LIFTING SOUTHWEST OF
BLANCHARD...LOUISIANA. MAXIMUM WINDS WERE ESTIMATED BETWEEN 150-160
MPH WITH A PATH LENGTH OF 15.6 MILES AND A PATH WIDTH OF 0.75 MILES.


The Canton Tornado


The 2nd tornado was the EF-2 tornado that struck Canton in Van Zandt CO. Originally there was some confusion on whether this was one tornado or was the damage path two tornadoes. The final survey report indicates that this was only one tornado. Again below are three images showing velocity, reflectivity, and volumetric views. This storm had a nice velocity couplet as the tornado was crossing the hwy 19, I-20 intersection. Also you will notice a very strong hook echo with this storm. Again the volumetric image shows deep purple indicating a very strong updraft. This storm at one point was showing 3”+ hail on radar. I think the largest reported hail with this storm was golfball.







Below is from the National Weather Service :
...PRELIMINARY INFORMATION ON VAN ZANDT COUNTY DAMAGE SURVEY...

INFORMATION IN THIS MESSAGE SHOULD BE CONSIDERED PRELIMINARY AND
WILL BE SUBJECT TO CHANGE AS ADDITIONAL INFORMATION IS RECEIVED.
AN NWS STORM SURVEY TEAM SURVEYED DAMAGE ACROSS VAN ZANDT COUNTY ON
THURSDAY JANUARY 21 2010. THE DAMAGE OCCURRED ON WEDNESDAY JANUARY
20. THE DAMAGE PATH STARTED ON THE NORTHWEST SIDE OF CANTON NORTH OF
HIGHWAY 64 AND JUST WEST OF FM859. THE DAMAGE PATH ENDS IN THE
SILVER LAKE AREA IN THE EXTREME NORTHEAST CORNER OF VAN ZANDT
COUNTY.
IT IS NOT KNOWN AT THIS TIME IF THERE IS A SINGLE CONTINUOUS DAMAGE
PATH OR IF THERE ARE TWO OR MORE SHORTER PATHS ACROSS VAN ZANDT
COUNTY.
ALONG THE DAMAGE PATH...A SINGLE FAMILY HOME LOST ITS ENTIRE ROOF
AND PART OF ITS EXTERIOR WALLS. A NUMBER OF LARGE TREES WERE
UPROOTED...AND SEVERAL SHEDS AND OUTBUILDINGS WERE DAMAGED TO
VARIOUS DEGREES. A CHURCH WAS DESTROYED IN THE COMMUNITY OF STARR.
EYEWITNESS REPORTS...RADAR INFORMATION...AND DAMAGE PATTERNS SUGGEST
THAT A TORNADO WAS RESPONSIBLE FOR THE SIGNIFICANT DAMAGE. BASED ON
THE SURVEY...THE TORNADO HAS BEEN ASSIGNED AN EF2 ON THE ENHANCED
FUJITA SCALE WITH PEAK WINDS IN THE 110 TO 120 MPH RANGE.


The Henderson CO. Tornadoes

The next 2 tornadoes were spawned from a supercell thunderstorm over southeast Henderson counties in the communities of Larue, Poynor, and Coffee City. Again the three images below show the storm as it was producing tornadoes.








Below is from the National Weather Service :

PRELIMINARY INFORMATION ON HENDERSON COUNTY DAMAGE SURVEY...

INFORMATION IN THIS MESSAGE SHOULD BE CONSIDERED PRELIMINARY AND
WILL BE SUBJECT TO CHANGE AS ADDITIONAL INFORMATION IS RECEIVED.
AN NWS STORM SURVEY TEAM SURVEYED DAMAGE ACROSS HENDERSON COUNTY ON
THURSDAY JANUARY 21 2010. THE DAMAGE OCCURRED ON WEDNESDAY JANUARY
20. THE SURVEY FOUND A DISCONTINUOUS DAMAGE PATH FOR A TOTAL OF
SEVEN MILES ACROSS SOUTHERN HENDERSON COUNTY.
TWO TORNADO TRACKS WERE OBSERVED. THE FIRST TORNADO STARTED SOUTH OF
THE CITY OF LARUE AND TRACKED EAST NORTHEAST. EXTERIOR WALLS
COLLAPSED ON SOME STRUCTURES. THIS TORNADO WAS RATED EF2 ON THE
ENHANCED FUJITA SCALE WITH ESTIMATED MAXIMUM WINDS AROUND 130 MPH.
ESTIMATED PATH WIDTH WAS 200 YARDS.

THE SECOND TORNADO STARTED NEAR POYNOR AND TRACKED NORTHEAST TOWARD
COFFEE CITY. A MOBILE HOME WAS DISLODGED AND A WOOD FRAMED HOME HAD
SIGNIFICANT DAMAGE. TREE DAMAGE WAS NOTED ALONG A THREE MILE PATH
WITH AN AVERAGE WIDTH OF ABOUT 100 YARDS. THIS TORNADO WAS RATED EF1
ON THE ENHANCED FUJITA SCALE WITH ESTIMATED PEAK WINDS IN THE 90 TO
100 MPH RANGE.


The Smith CO. Tornadoes

The same storm that produced two tornadoes in Henderson CO moved into Smith CO and produced an additional two tornadoes, an EF-0 in Flint and an EF-1 near Whitehouse. As this storm moved through southern Smith CO, it was showing very strong rotation on both the National Weather Service NEXRAD and our own Stormtraker Live Doppler Network. The communities of Noonday, Gresham, Flint, and Whitehouse are very lucky. With this type of circulation we would normally have seen a long track tornado. However the circulation stayed off the ground for most of its time in Smith CO. The rotation was much stronger over Smith CO than when this storm produced an EF-2 tornado in Henderson CO.







Below is from the National Weather Service:

THE NATIONAL WEATHER SERVICE COMPLETED A DAMAGE SURVEY IN SMITH
COUNTY...TEXAS...NEAR NOONDAY. A WEAK EF0 TORNADO FIRST TOUCHED DOWN
IN A SUBDIVISION ALONG SOUTHERN TRACE CIRCLE WHERE SHINGLES WERE
PEELED OFF SEVERAL HOMES AND A TRAMPOLINE WAS THROWN UP ONTO A HOME.
SEVERAL FENCES WERE ALSO BLOWN DOWN. THE TORNADO CONTINUED EAST ONTO
WALNUT HILL DRIVE WHERE SPORADIC TREE DAMAGE WAS OBSERVED AS WELL AS
MINOR DAMAGE TO SEVERAL HOMES ALONG THE STREET. MAXIMUM WINDS WERE
65-70 MPH. PATH LENGTH WAS 1.5 MILES WITH A PATH WIDTH OF 75 YARDS.
THE NATIONAL WEATHER SERVICE COMPLETED A SECOND DAMAGE SURVEY IN
SMITH COUNTY...TEXAS...NEAR WHITEHOUSE.

AN EF1 TORNADO BRIEFLY TOUCHED DOWN NEAR THE INTERSECTIONS OF OSCAR BURKETT ROAD AND JOYE LANE (CR 2192). A SMALL METAL GARAGE WAS DAMAGED WHERE A COUPLE OF
THE WALLS WERE BLOWN OUT. A LARGE PINE TREE WAS SNAPPED ALONG CR
2192 CLOSE TO THE GROUND. SEVERAL LARGE LIMBS WERE SNAPPED OUT OF A
CEDAR TREE AS WELL AS OTHER TREES ALONG THE PATH. FURTHER NORTHEAST
ON THE NORTH SIDE OF CR 2192...A SMALL BARD WAS DESTROYED AND TIN
ROOF PANELS WERE PEELED FROM ANOTHER BUILDING. MAXIMUM WINDS ARE
ESTIMATED AT 80-85 MPH. THE PATH WAS 0.5 MILES LONG AND 75 YARDS
WIDE.



The Harleton Tornado

The next tornado was a surprise, the Harleton tornado. The storm that produced this tornado started in Gregg CO and actually showed good signs of rotation on our Stormtracker Live Doppler Radar but was not as great on the National Weather Service NEXRAD. Since the national Weather Service does not have access to our radar, there was only a severe thunderstorm warning issued on this storm. As this storm moved into Harrison CO, the rotation on our radar weakened significantly. The actual storm itself was showing a weakening sign as well. Looking at the radar grabs you will notice the cell over Harleton is very small. Also notice the rotation on the velocity image is weak and broad. The volumetric scan shows deep convection, but no large areas of deep purple so the updraft was not as strong as with previous storms. This storm showed very little evidence of a tornado but it did produce. An EF-1.







Below is from the National Weather Service:
THE NATIONAL WEATHER SERVICE COMPLETED A DAMAGE SURVEY IN HARRISON
COUNTY TEXAS NEAR HARLETON...TEXAS. AN EF1 TORNADO TOUCHED DOWN
ALONG CENTRAL AVENUE...UPROOTING TREES AND CAUSING MINOR DAMAGE TO
AWNINGS ON HOMES ALONG THE STREET. THE TORNADO TRAVELED NORTHEAST
AND UPROOTED MORE TREES AND CAUSED MINOR ROOF AND STRUCTURAL DAMAGE
TO 2 BRICK BUILDINGS AND ONE METAL BUILDING ALONG HWY 154. THE TORNADO
LIFTED JUST ACROSS HWY 154. WINDS WERE ESTIMATED AT 95 TO 105 MPH. THE PATH LENGTH WAS 0.5 MI...AND THE WIDTH WAS 50 YARDS.


The Sulphur Springs Tornadoes

The next two tornadoes were produced near Sulphur Springs Hopkins CO. Both of these tornadoes were rated EF-0. The images below show the storm as it produced its first tornado along HWY 19 south on I-20.




Below is from the National Weather Service:
INFORMATION IN THIS MESSAGE SHOULD BE CONSIDERED PRELIMINARY AND
WILL BE SUBJECT TO CHANGE AS ADDITIONAL INFORMATION IS RECEIVED.

AN NWS STORM SURVEY TEAM SURVEYED DAMAGE IN HOPKINS COUNTY ON
THURSDAY JANUARY 21 2010. THE DAMAGE OCCURRED ON WEDNESDAY JANUARY
20. THE SURVEY FOUND TWO PATHS OF DAMAGE INDICATIVE OF A
DISCONTINUOUS TORNADO TRACK. BECAUSE OF THE LACK OF COHERENT DAMAGE
BETWEEN THE PATHS...THE PRELIMINARY FINDINGS WILL LIST THE PATHS AS
SEPARATE TORNADOES.

THE FIRST TORNADO TOUCHED DOWN AROUND 615 PM APPROXIMATELY 4 MILES
SOUTHWEST OF SULPHUR SPRINGS. THE TORNADO TRACKED TO THE EAST-
NORTHEAST FOR 1.5 MILES. ONE MOBILE HOME WAS DESTROYED...RESULTING IN
INJURIES TO TWO OF ITS OCCUPANTS. IN ADDITION...A PRE-FABRICATED
METAL BUILDING ON STATE HIGHWAY 19 (JUST SOUTH OF COUNTY ROAD 174)
SUSTAINED CONSIDERABLE DAMAGE. THE DAMAGE WAS CONSISTENT WITH THE
UPPER END OF THE EF0 RATING ON THE ENHANCED FUJITA SCALE...WITH WIND
SPEEDS ESTIMATED AT NEAR 80 MPH.

THE SECOND TORNADO PATH BEGAN ONE MILE SOUTH OF THE CENTRAL BUSINESS
DISTRICT OF SULPHUR SPRINGS AROUND 630 PM...AND CONTINUED 1.5 MILES
TO THE NORTHEAST. DURING THE 10 MINUTES THE TORNADO WAS ON THE
GROUND...AROUND 50 HOMES SUFFERED SOME DEGREE OF ROOF DAMAGE...TWO
OF WHICH SUSTAINED MORE SEVERE DAMAGE AFTER BEING IMPALED BY LARGE
TREE BRANCHES. THIS DAMAGE WAS CONSISTENT WITH SPEEDS OF 80 TO 85
MPH...ALSO ON THE UPPER END OF THE EF0 RATING.




The Geneva Tornado

The 10th final tornado I will discuss was near Geneva in Sabine CO. This was the first tornado warning issued in Texas on this day. A strong area of rotation is shown on the velocity data below. Also you will see on the reflectivity a doughnut hole where a red circle surrounds an area of yellow. This indicates the rotation was wrapped in precipitation.




Below is from the National Weather Service:
THE NATIONAL WEATHER SERVICE COMPLETED A DAMAGE SURVEY IN SABINE
COUNTY...TEXAS...NEAR GENEVA. AN EF1 TORNADO TOUCHED DOWN ALONG FM
330 TOPPLING AND UPROOTING SEVERAL LARGE TREES. ONE HOME HAD MINOR
ROOF DAMAGE ALONG WITH MOST OF ITS SHINGLES STRIPPED OFF...WHILE
ANOTHER HAD ITS OUTSIDE STORAGE SHED DESTROYED. WINDS WERE
ESTIMATED TO BE FROM 95 TO 105 MPH. THE PATH LENGTH WAS 500
YARDS...AND THE WIDTH WAS 150 YARDS.

Thursday, January 21, 2010

Time Lapse of the Smith County Supercell

video

A big thanks to Tim Ogrodnik of Flint who put this series together for me. You can see the rotation of the storm as it moves towards Tom. Also notice the wall cloud during lightning shots. The last image in the series shows the funnel that was the Flint Tornado. I will try to increase the contrast so it is visible soon.

Wednesday, January 20, 2010

Severe Weather Possible This Evening

Tornado off of Newport Beach. Crazy right?! @SabrinaBryan on Twitpic

(Photo Above From Twitter of a California Waterspout/Tornado Yesterday)

We are still looking for a few severe thunderstorms to develop this afternoon and evening as a strong storm system heads towards East Texas. Right now a fairly strong cap is in place, or warm air just off the surface, keeping thunderstorm development at bay. But as surface temperatures warm, and the upper air disturbance nears, this cap will erode and we will see rapid development of storms. Right now it does appear the atmosphere will be unstable enough to produce large hail, greater than golfball size in a few areas. We could also see a few reports of wind gusts near 60 mph along with an isolated tornado. Right now the tornado threat does not look that great however, there is a window of opportunity for tornado development between 6 and 9 pm this evening as a meso low pressure develops near Dallas, forcing the surface winds out of the southeast, increasing the low level wind shear.

Tuesday, January 19, 2010

Severe Storms Possible Tomorrow



Most of East Texas is still under the threat of severe weather tomorrow afternoon and evening. By analysing the sounding data above, looks like the main threat tomorrow will be a large hail event with a few high wind reports. I can't rule out an isolated tornado but as of now, the greatest tornado threat appears to be to our southeast. The hodograph indicates 0-1kn shear 6 m/s or about 12 knots. We normally like to see 0-1km shear at or above 20 knots for tornado development. However, when you look at the hodograph for 0-6 km shear we see there is around 37 m/s or 71 knots of shear. More than enough for supercell development. So it looks as though we will see sustained rotation updrafts however, the low level vorticity needed for tornado development is lacking.



The above image is of the MLCAPE forecast for tomorrow afternoon. Notice that all of East Texas is in the light blue which indicates CAPE values between 1000 - 1500 J/kg. This is more than enough instability this time of the year. The atmosphere is not as deep as we would find during the spring months thanks to the lower temperatures in the mid levels of the atmosphere. This should lead to a few storms producing large hail, maybe as large as golfballs.




The final image above shows the dewpoints, in the low 60s for most of East Texas, and streamlines, or surface wind direction. Models are hinting at a meso low developing near Dallas late tomorrow. If this low is deepens surface winds will back more out of the southeast and this would increase the tornado threat. So the next 36 hours does have the potential to produce severe weather but, at this time it does not look like a repeat of December 23rd 2009.

Friday, January 15, 2010

Severe Threat Next Wednesday Looks Weaker

What a difference a day makes. This time yesterday the "red flag" was flown as forecast models were hinting at a potential tornado outbreak nest Wednesday. Since yesterday morning, forecast models have trended away from a major severe weather event. We are still looking at the possibility of strong storms with small hail but the overall severe threat looks pretty minimal. Below is the new forecast sounding for Wednesday. The timing has moved forward about 6 hours and the amount of CAPE has been nearly cut in half (see yesterday's forecast sounding for Wed). This indicates that the storms' updrafts would be much weaker than what was forecast earlier. So the threat of large hail has diminished greatly. In addition you will notice that the wind speeds through the CAPE have weakened nearly 50 knots making the threat for severe winds gusts much less as well. .


Finally for the tornado threat. The 0-1km SRH helicity is much less than indicated by yesterday's hodograph


Notice the low level turning of wind with height is very small, no greater than we would find on a typical summer afternoon thunderstorm event. So the tornado threat has gone from very large to almost zero. Now again, we are still a long way out from this event and this storm system could become much stronger than currently forecast. My forecasting experience tells me this system is probably being advertised too weak and a blend of yesterday's model run with today's would probably produce the best forecast. This would lead to a few strong to severe storms and maybe an isolated tornado but, the tornado outbreak I was thinking could happen yesterday, more than likely will not occur.

Thursday, January 14, 2010

Spring Storms Possible Next Week



After a couple of weeks of cold weather across East Texas, changes in the upper air pattern could lead to some strong storms, including severe weather, by mid week. A negatively tilted trough will be swinging through the southern plains helping to bring in Gulf moisture and warmer air across East Texas by Wednesday afternoon. Dewpoint temperatures will reach the lower to middle 60s across most of East Texas making Wednesday fairly muggy (see below).



Temperatures Wednesday night into Thursday morning will remain in the lower to middle 60s as well, much above normal (see below). This will allow for thunderstorm activity to continue well into the night. Right now it look as though high temperatures will top of Wednesday afternoon in the middle to upper 60s but, if this system is as strong as advertised I would not be surprised to see a few 70s across East Texas, especially south of I-20.



The warm moist air at the surface combined with colder temperatures aloft will provide plenty of instability for thunderstorm development. The surface based Lifted Index will be between -4 and -8 Wednesday afternoon and evening, more than enough to support severe thunderstorm growth (see below).



The amount for CAPE (convective available potential energy) is forecast to be very high as well for this time of the year. Many times in the cold season we see severe weather events in a low instability high shear environment, like our tornado outbreak last month. CAPE values were running between 500 and 1000 that day and you can see we could have values between 1000 and 2000 this upcoming Wednesday (see below).



The next ingredient needed for supercell development is wind shear. 0-6km shear really needs to be greater than 30 knots to provide the best environment for supercell development and by looking at the image below, most of East Texas has 0-6km wind shear 30 and 50 knots. This is not as much as was advertised for the 12/23/09 event (0-6 km shear between 50 and 70knots) but is enough to produce supercells, especially with CAPE values at or above 1500 J/kg.



The forecast sounding and hodograph paint a potentially dangerous situation Wednesday afternoon and evening. Looking at the sounding we can evaluate the severe weather potential (see below). We see positive CAPE with the yellow line, parcel temperature, well to the right of the environmental temperature, red line. Nearly half of this CAPE is between the -10°C and -30°C isotherm, or the hail growth region. With positive CAPE and wind shear, large hail would definitely be a threat. We can also see the winds in the positive CAPE region as high as 70 knots. The forward flank downdrafts of any storm that develops could tap this wind and bring it to the surface. So high winds would be a threat as well.



Finally for the tornado threat. The hodograph shows a large clockwise turning of the winds with height. Below is an image of the 0-1km hodograph. This layer of the atmosphere is where the air is ingested into the storm. So there would be plenty of vorticity available in the lower levels for low level mesocyclone development which could lead to isolated tornadoes.



Overall it does appear over the next week to ten days the weather pattern will be more like spring than we would find in January. Any time we see warm moist air from the Gulf surge northward we have to be on the watch for severe weather. The event forecast for Wednesday is many days out and we will probably see some overall changes in the forecast between now and then. I do want to stress to long range models have been performing fairly well 6 to 7 day s out as of late. Again, the event on 12/23/09 was forecast well in advanced. If the current forecast trend continues, we could see another significant severe weather event.

Saturday, January 9, 2010

Coldest Night in 14 Years..Could Be Colder Tonight!


With clear skies and calm winds, East Texas was greeted with the coldest temperatures in 14 years last night. Low temperatures were between 10°F and 15°F just about area wide, with a few places dipping below 10 degrees(Winona MADIS station dropped to 9°F and yours truly dropped to 8°F). In addition to the bitter cold, the light winds allowed for a unique type of frost to form last night. Normally here in East Texas when we see frost we have dew form on objects and then freeze as the temperature of the objects fall below freezing. Last night a process called deposition occurred were the water vapor in the atmosphere went from a gas directly to a solid. This occurs when objects are very cold and come into contact with water vapor. Instead of condensation forming on the object, ice crystals begin to grow, just like snowflakes. If you look at the photo above you can see what appears to be small snowflakes. Notice the branching crystal growth. This is called dendritic crystal growth, the way snowflakes form in the atmosphere. The optimal temperature for this to occur is 14°F (-10°C) or colder. Objects around East Texas last night were easily colder than 14°F allowing for the snow like frost to form.

Light winds and sunny skies today will allow for a rapid warm up. Many of us will hit the freezing mark or a little higher. It will fell much warmer today due to the lack of wind. However, another very cold night is in store for East Texas tonight as light winds and clear skies allow the mercury to drop between 10°F and 15°F again in most places.

Monday, January 4, 2010

The coldest temperatures in 14 years are on the way to East Texas

Image From NWS Fort Worth

A strong area of arctic will be moving south across the Nation bringing with it some of the coldest air in years. Right now it appears the front will move through early Thursday morning, before sunrise. Along and behind this front we will see scattered showers develop. As the cold air moves in, these showers will change to light snow or flurries Thursday morning. As the arctic air continues to move into the area, flurries will move out and very cold temperatures will move in. Our high temperature on Thursday will occur early in the day before sunrise. By Thursday afternoon most of East Texas will see temperatures in the 20s with wind chills approaching zero at time.

On Friday morning the mercury will bottom out in the middle teens in most areas. It has been many years since temperatures dropped to 15 degrees or below. The last time this occurred in Tyler was on Feb. 4th, 1996. For Longview the last time the temperature dropped to 15 was on Dec. 25th, 1990. And in Lufkin, the last time the temperature was at or below 15 degrees was on Dec. 24th 1989.

So if we do see lows at or below 15 degrees, we will be seeing temperatures that many of us haven’t seen in nearly a generation. But will we set record lows? Our coldest temperatures will be Friday and Saturday morning. The record low for Tyler seems to be safe at 8 degree on the 8th and 10 degrees on the 9th. The record lows for Longview appear safe with both morning record lows being 13 degrees however, it could be close. For Lufkin the record low on the 8th is 15 degrees and on the 9th is 16 degrees. So if any city will set a new record low, Lufkin probably has the best chance.

Dark Blue Shows Most Of East TX Between 10 and 15 Degrees Sat.AM

Incase you were wondering when the last time East Texas has seen temperatures below 10 degrees, all three cities reported temperatures at or below 10 degrees on December 24th 1989, when most areas of East Texas were between 0 and 5 degrees. Although I don’t think we will see temperatures below 10 degrees, if skies are clear and winds are light, someone could get close on Saturday Morning.

Stay Warm!