SE TX/SW LA weather: Much cooler and WET after Tuesday

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Ed Mahmoud

Re: SE TX/SW LA - Cold, wet weekend ahead

#721 Postby Ed Mahmoud » Wed Feb 13, 2008 8:58 am

Posted this on TX Winter WX thread, but it also would fit (the heavy rain/severe angle this weekend) here.


Ed Mahmoud wrote:I just PM'd WxMan57 and requested his presence on this thread. We need professional help!


6Z WRF holds out hope for a little sleet, or dare I say, maybe even graupel briefly Saturday am.


Not totally sure what the 6Z GFS is showing for Sunday. North Texas the 1000-500 mb thickness falls below 545 dm, and 850 mb temps approach freezing, beneath the upper low, that could be snow. Or maybe not, as my AccuWx PPV GFS raw surface temp is 4ºC.


On a different subject, that model run keeps the front very close to IAH the whole time, so the heavy rain/severe weather thing can't be ruled out.


Friday afternoon, 250 to 500 J/Kg CAPE isn't superhigh, but 15 m/s deep layer shear (~ 30 knots), while not super-high either, should at least support a few strong (maybe not severe) storms.

Image

Saturday afternoon looks a bit more favorable, per 6Z GFS, almost 1000 J/Kg around HOU, and about 35 knots deep shear, and plenty of upward motion.

Image
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Re: SE TX/SW LA - Cold, wet weekend ahead

#722 Postby Ed Mahmoud » Wed Feb 13, 2008 9:01 am

6Z GFS MOS shows over 4 inches of rain at IAH Friday afternoon to Sunday morning...
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Re: SE TX/SW LA - Cold, wet weekend ahead

#723 Postby Ed Mahmoud » Wed Feb 13, 2008 11:16 am

Ed Mahmoud wrote:¡¡¡¡¡¡ Oh Please Oh Please Oh Please!!!!!


12Z WRF suggests some meaningful winter weather in SE Texas!
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Re: SE TX/SW LA - Cold, wet weekend ahead

#724 Postby Ed Mahmoud » Wed Feb 13, 2008 1:02 pm

Ed Mahmoud wrote:
Ed Mahmoud wrote:¡¡¡¡¡¡ Oh Please Oh Please Oh Please!!!!!


12Z WRF suggests some meaningful winter weather in SE Texas!


OK, 12Z GFS is a complete kill joy on this, holding up front right near HOU, but, it does track a surface low right up the coast Saturday afternoon and evening, and coastal locations like Beaumont and Galveston would be right on/barely North of the warm front, potentially a dicey place to be for rotating storms.

Image
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Re: SE TX/SW LA - Cold, wet weekend ahead

#725 Postby Ed Mahmoud » Wed Feb 13, 2008 4:37 pm

18Z WRF looks like the 12Z globals, front staying close, no winter wx here in SE Texas. But, like the 12Z GFS, a low moving along/just inland/just offshore Texas, so there could be a narrow band of potentially tornadic storms along the coast.
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#726 Postby Extremeweatherguy » Wed Feb 13, 2008 11:59 pm

Run down of the 00z NAM and 00z GFS...

00z GFS
This model run shows the front moving into our region on Friday evening, but then stalls it and shifts it back west overnight. By midday on Saturday the model shows us into upper 60s to lower 70s with a warm flow being brought in from the gulf as a surface low forms in southern Texas. Being on the northeastern side of this low and in the warm sector, the GFS scenario looks favorable for a severe weather risk during the day Saturday. Eventually though, by Sunday morning, the GFS finally decides to shift the front back east (proceeded by a strong squall line), and by Sunday afternoon our temperatures cool into the 50s with clearing, breezy skies. Monday morning then falls into the 30s and 40s with mostly clear to partly cloudy skies across the region.

My take: I highly doubt this scenario plays out. Yes, it is "possible", but not very likely (IMO). The chance of the front moving into our region on Friday and then shifting back west until Sunday is a little far fetched. I think the GFS may be underestimating the push this shallow cold air may have, and therefore is too quick to shunt it out of the region (a typical error). I will say though that IF this scenario does play out, then we will need to watch the severe potential closely. We could easily wind up seeing a decent severe outbreak out of this kind of setup with tornadoes a real possibility.

00z NAM
This model run moves the surface front into Houston by very early Saturday morning (before sunrise) and then stalls it (without pushing it back west like the GFS). This scenario would mean a very split forecast for SE Texas on Saturday. Northwest zones would likely not get out of the 40s during the day, while coastal sections could approach 70F. In Houston proper, high temperatures would likely range from the low/mid 50s NW to the low/mid 60s SE. Rain would be widespread during this, but any severe threat would likely be limited to areas SE of Houston. By Sunday morning, the NAM starts to really look interesting. It pushes the front offshore and it begins to pull the strong ULL across the state. Underneath the ULL, the NAM is showing an area of sub-0C 850mb temperatures and plenty of wrap around moisture (with freezing levels <2000 feet). This kind of setup would be capable of some snow/ice mixing in central Texas and that could possibly spread eastward under the ULL during the day...so it would be something to watch closely here in SE Texas as well.

My take: This scenario is more believable than the GFS. It stalls the front overhead instead of shifting it well back to the west, which seems to be a much more plausible scenario. We would still see a significant heavy rain threat out of the NAM scenario, but the setup would be much less favorable for tornadoes in the Houston metro area. One fun thing about this model is that cold air it is showing under the ULL on Sunday. It would definitely make for an interesting day on Sunday watching to see if any flakes or sleet pellets were reported under it as it moved eastward.


BTW - - The latest 00z GFS MOS is one of the warmest scenarios out there right now and is quite close to the operational GFS (for Saturday, especially). It is showing a warm and muggy high of 71F on Saturday and 70F on Sunday, and it also shows dewpoints into the mid 60s with an 80-100% chance of precipitation. This would definitely be a good setup for potential strong/severe storms and heavy rain.
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#727 Postby Extremeweatherguy » Thu Feb 14, 2008 6:42 am

Well the SPC is really going crazy for Saturday! They currently have SE Texas in a hatched 30% area, but this could easily be upgraded to a moderate risk zone in future updates...which is something we have not seen in a while..

http://www.spc.noaa.gov/products/outloo ... b_1100.gif

...SOUTHERN PLAINS/LOWER MISSISSIPPI VALLEY...
PERHAPS THE BIGGEST SOURCE OF FORECAST UNCERTAINTY FOR THIS PERIOD
CONCERNS JUST HOW FAST THE SHALLOW COLD SURFACE BASED AIR MASS
MODIFIES ACROSS CENTRAL TEXAS INTO TEXAS GULF COASTAL AREAS...IN THE
WAKE OF THE ANTICIPATED COLD INTRUSION LATE THIS WEEK. ASIDE FROM
BOUNDARY LAYER DESTABILIZATION ISSUES...THIS WILL IMPACT THE
STRENGTH/LOCATION OF SURFACE CYCLOGENESIS...WHICH SHOULD INITIATE
WITH THE APPROACH OF THE UPPER SYSTEM. IT CURRENTLY SEEMS A BIT
MORE PROBABLE THAT THIS PROCESS WILL BE WEAKER/SLOWER AND ALONG A
BAROCLINIC ZONE IN CLOSER PROXIMITY TO COASTAL AREAS...THAN
CURRENTLY INDICATED BY EITHER THE ECMWF OR GFS.

REGARDLESS...THIS SHOULD ONLY IMPACT THE TORNADO POTENTIAL. IF NOT
NEAR THE SURFACE...JUST ABOVE...THERMODYNAMIC PROFILES ACROSS MUCH
OF TEXAS ARE EXPECTED TO BECOME CONVECTIVELY UNSTABLE. AND...A
LOADED GUN TYPE STRUCTURE SHOULD EVOLVE...PARTICULARLY ACROSS PARTS
OF SOUTH CENTRAL INTO SOUTHEAST TEXAS...AS A SOUTHERLY LOW-LEVEL JET
CONTINUES TO STRENGTHEN OFF THE WESTERN GULF OF MEXICO...BENEATH AN
ELEVATED MIXED LAYER. BY LATE SATURDAY AFTERNOON...VERY LARGE
CLOCKWISE CURVED LOW-LEVEL HODOGRAPHS ARE FORECAST TO EVOLVE BENEATH
50+ KT SOUTHERLY 850 FLOW...WHILE DEEP LAYER SHEAR INTENSIFIES AS A
STRONG SOUTHWESTERLY UPPER JET NOSES THROUGH THE LOWER RIO GRANDE
VALLEY.

THIS ENVIRONMENT WILL BE FAVORABLE FOR SUPERCELLS...AT LEAST CAPABLE
OF PRODUCING VERY LARGE HAIL AND DAMAGING WIND GUSTS. WHILE
DISCRETE ACTIVITY IS POSSIBLE...STRONG MID-LEVEL FORCING ASSOCIATED
WITH THE APPROACHING IMPULSE IS EXPECTED TO SUPPORT A SEVERE SQUALL
LINE...WHICH SHOULD DEVELOP EASTWARD OUT OF CENTRAL TEXAS ACROSS
TEXAS COASTAL AREAS AND PARTS OF THE SABINE VALLEY BEFORE WEAKENING
SATURDAY NIGHT.
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Re: SE TX/SW LA - Cold, wet weekend ahead?

#728 Postby jasons2k » Thu Feb 14, 2008 8:22 am

Looks like the warmer scenario wasn't so unlikely after all - latest from Jeff Lindner:

***Severe Weather and excessive rainfall possible this weekend***

Major changes to temperatures needed this morning for Friday and Saturday.


Impressive upper air storm system will affect TX this weekend with increasing threat of severe weather and flooding rains. Water vapor shows upper trough digging southward down into the SW US and northern Mexico as arctic boundary drops down the plains. Deep upper low will cut-off from the main northern flow over the next 24 hours while arctic boundary spills into TX and stalls across our northern counties. Will need to raise temps. on Friday by about 15 degrees from yesterday to account for the front stalling north of the region. Will also reduce rain chances/delay them until Friday afternoon.

Friday afternoon:

Upper low begins to push eastward allowing impressive lift to overspread the region while low level jet of 40-50kts develops late in the afternoon off the western Gulf of Mexico. Mid level shear values increase into the 40-60kt range and expect thunderstorms to quickly develop on nose of low level jet. Instability will be limited by clouds and although shear values do support rotating updrafts…the main severe threat appears to be large hail and damaging winds.

Friday night:

Deep…almost tropical like moisture pours into the region from the Gulf with PWS rising to near 1.8”…ouch! Expect numerous thunderstorms to develop and train NE across the region. Rainfall rates will increase as moisture deepens. Still expect a severe threat given good low level shear profiles and strong lift.

Saturday:

*A rough weather day with good severe threat including tornadoes*


Deep upper low ejects into TX with strong 120kt jet core rounding the base of the trough and plowing into the region. Surface low will be forced somewhere along the coast or within about 100 miles inland with the entire region likely warm sectored. This will require temps. to be warmed greatly on Saturday by about 20 degrees over yesterday. This also greatly enhances the severe weather threat. After about 18Z (noon) Saturday low level hodographs show strong low level turning with good low level shear developing as low level jet intensifies and strong mid levels winds impinge on the region. Expect supercell structured storms to develop in strongly forced ascent pattern ahead of strong linear forcing along cold front in C TX. Surface based supercells rooted near the surface will be rotating in their updrafts and the resultant tornado threat will be increasing Saturday after noon into the evening hours. Given the amounts of low level shear and a highly moist air mass a few strong tornadoes will be possible.

At the same time as the upper trough crosses the state strong forcing over C TX will develop a squall line along the arctic frontal boundary. Impressive 120kt jet core will punch into the back side of the developing squall line in the 300pm-900pm Saturday evening. Expect the line to grow upscale into a linear MCS as it races ESE into SE TX after dark Saturday. Favorable low level jet inflow and good dynamics all point to all severe modes with this line including embedded supercells producing tornadoes and stand alone supercells with a greater tornado threat ahead of the main line. Entire mess should clear the area by 12Z Sunday (600am)…but we will really be under the gun for about a 24-36hr period.

Hydro:

Concern is growing with the rainfall potential given excessive amounts of moisture and sub-tropical tap that will develop. One good piece of news is that it appears the surface front progged to stall along the coast yesterday will now stall well inland and focus the heaviest rains just north of our region…although one must remember that what falls north of us will make its way through the region to reach the Gulf. Feel HPC is low on its QPF of basin wide 1” on Friday and 2-3” on Saturday. Given PWS increasing to near and over the magical +2 SD expect storms will be prodigious rainfall producers. Will go with widespread event totals of 2-3” with isolated amounts of 5-7”. Would not be surprised if a couple locations pulled off 10” given the prolonged nature of the event and potential for convective training and HP supercell production. Such setups can produce a lot of rain in a very short period of time. Will have to watch for any kind of low level outflow boundaries that may develop and focus the rains along a training corridor…as that is where the greatest flood threat will lie.
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#729 Postby KatDaddy » Thu Feb 14, 2008 9:09 am

Everyone in SE TX best be aware of weather developments this weekend. This looking like a very dangerous weather event. Its not often we get conditions that create numerous rotating tornadic supercells.
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Re: SE TX/SW LA - Cold, wet weekend ahead?

#730 Postby JenBayles » Thu Feb 14, 2008 2:59 pm

Oh boy - here come the Spring storms. I've already given Dave orders to clean out the gutters this afternoon, and I'm cleaning leaves out of our floodways under the fences. We got one awful squall from Allison where we had to punch out the fence boards at the sides of the house to allow the back yard to drain faster. The water came up 2 feet along the walls of our house in about 15 minutes back then, so I'm paranoid about any debris blocking the water flow now.
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#731 Postby Extremeweatherguy » Thu Feb 14, 2008 5:25 pm

After looking at the models and the forecasts this afternoon, I think it is becoming more and more likely that this front will wind up stalling. I just find it hard to believe that all these forecasters and models will be wrong in the end. Yes, it is definitely still possible that the front does not stop and makes it to the coast, but ATM I think the chances of that happening are growing smaller and smaller. This front will likely be one of those few that defies what is "supposed to happen" with these shallow airmasses.
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Re: SE TX/SW LA - Severe weather Fri/Sat?

#732 Postby jasons2k » Thu Feb 14, 2008 5:45 pm

Welcome to the fold EWG :D

This trough is negatively tilted and it means business:

http://www.nco.ncep.noaa.gov/pmb/nwprod ... _054.shtml
http://www.nco.ncep.noaa.gov/pmb/nwprod ... _060.shtml
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#733 Postby Extremeweatherguy » Thu Feb 14, 2008 9:51 pm

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
846 PM CST THU FEB 14 2008

.DISCUSSION...
ONLY FORECAST CHANGE NEEDED THIS EVENING IS TO RAISE GALVESTON`S
OVERNIGHT LOW TEMPERATURE A DEGREE BASED ON THE CURRENT READING
AND ANTICIPATED TRENDS. THE REST OF THE FORECAST LOOKS GOOD.

15/00Z NAM IS STILL INDICATING A NASTY AND POTENTIALLY DANGEROUS
SATURDAY AFTERNOON AND EVENING. PARAMETERS FOR SEVERE WEATHER STILL
LOOK VERY GOOD WITH THE NEW MODEL RUN - DEEP MOISTURE...VERY STRONG
LOW LEVEL JET...VERY STRONG LIFT AND IMPRESSIVE SPEED AND DIRECTIONAL
SHEAR - AS THE UPPER LOW NOW OVER SOUTHERN CALIFORNIA MOVES ACROSS
TEXAS. SPC HAS OUR ENTIRE AREA UNDER SLIGHT RISK ON THEIR DAY3 OUTLOOK.
WOULD NOT AT ALL BE SURPRISED IF THIS IS UPGRADED TO A MODERATE RISK
AS THE EVENT GETS CLOSER. AS STATED IN OUR LATEST HAZARDOUS WEATHER
OUTLOOK UPDATED THIS AFTERNOON...SOUTHEAST TEXAS RESIDENTS ARE ENCOURAGED
TO CLOSELY MONITOR THE WEATHER FORECAST DURING THE NEXT TWO DAYS.
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Re: SE TX/SW LA - Severe weather Fri/Sat?

#734 Postby Ptarmigan » Thu Feb 14, 2008 10:46 pm

Should be an interesting weekend.
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#735 Postby Extremeweatherguy » Thu Feb 14, 2008 10:57 pm

The 00z GFS continues to show a dangerous Saturday with severe weather likely across SE Texas...

http://www.nco.ncep.noaa.gov/pmb/nwprod/analysis/namer/gfs/00/fp0_030.shtml
http://www.nco.ncep.noaa.gov/pmb/nwprod/analysis/namer/gfs/00/fp0_036.shtml
http://www.nco.ncep.noaa.gov/pmb/nwprod/analysis/namer/gfs/00/fp0_042.shtml
http://www.nco.ncep.noaa.gov/pmb/nwprod/analysis/namer/gfs/00/fp0_048.shtml
http://www.nco.ncep.noaa.gov/pmb/nwprod/analysis/namer/gfs/00/fp0_054.shtml

Supercells will probably be the primary severe threat during the afternoon, followed by a strong squall line (perhaps even in the form of a "derecho") during the evening hours.
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#736 Postby CajunMama » Thu Feb 14, 2008 10:57 pm

We've got an 80% chance of rain saturday. Boooooo! It's fan day for university of louisiana baseball.
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Re: SE TX/SW LA - Severe weather Fri/Sat?

#737 Postby Stratosphere747 » Fri Feb 15, 2008 1:52 am

Image
Image

NWS STORM PREDICTION CENTER NORMAN OK
1204 AM CST FRI FEB 15 2008

VALID 161200Z - 171200Z

...THERE IS A MDT RISK OF SVR TSTMS OVER PARTS OF SOUTHEAST THROUGH
EAST CNTRL TX...

...THERE IS A SLGT RISK OF SVR TSTMS FROM TX INTO THE LOWER MS
VALLEY...

...SYNOPSIS...

SPLIT FLOW PATTERN WILL PERSIST THROUGH SATURDAY. MODEL CONSENSUS IS
THAT UPPER LOW CURRENTLY OVER THE SWRN U.S. WILL ADVANCE EWD THROUGH
TX SATURDAY AND INTO THE LOWER MS VALLEY SATURDAY NIGHT. SRN PORTION
OF COLD FRONT CURRENTLY EXTENDING FROM THE GREAT LAKES SWWD THROUGH
WRN TX WILL LIKELY STALL ACROSS S TX. THIS BOUNDARY WILL THEN BEGIN
TO LIFT NWD AS A WARM FRONT AS A STRONG SLY LOW LEVEL JET DEVELOPS
ACROSS TX.

...TX THROUGH THE LOWER MS VALLEY AREA...

OBSERVATIONS SHOW THE BOUNDARY LAYER CONTINUES TO MODIFY ACROSS THE
WRN GULF WITH UPPER 60S DEWPOINTS INDICATED OFF THE SERN TX COAST.
THE 00Z CORPUS CHRISTI AND BROWNSVILLE SOUNDINGS SHOW A DEEP AND
MOIST BOUNDARY LAYER OVERSPREAD BY A SUBSTANTIAL ELEVATED MIXED
LAYER. GIVEN THE FRONT IS NOT EXPECTED TO ADVANCE INTO THE
GULF...PARTIALLY MODIFIED GULF AIR WITH MID TO UPPER 60S DEWPOINTS
WILL LIKELY ADVANCE THROUGH THE WARM SECTOR ACROSS SOUTH AND CNTRL
TX AS THE WARM FRONT LIFTS NWD. ELEVATED STORMS WILL BE ONGOING
WITHIN ZONE OF STRONG WARM ADVECTION AND LIFT NORTH OF THE WARM
FRONT FROM PARTS OF CNTRL AND NWRN TX THROUGH E CNTRL AND NE TX.
THIS PRECIPITATION WILL LIKELY REINFORCE THE COOL AIR AND MAY SLOW
THE NWD PROGRESSION OF THE WARM FRONT. PRESENCE OF STEEP MID LEVEL
LAPSE RATES ASSOCIATED WITH THE EML ABOVE THE MOIST BOUNDARY LAYER
WILL LIKELY CONTRIBUTE TO MODERATE INSTABILITY IN WARM SECTOR OVER
SOUTH THROUGH E CNTRL TX.

PRIMARY UNCERTAINTY AT THIS TIME IS WHETHER OR NOT STORMS WILL BE
ABLE TO INITIATE WARM SECTOR AWAY FROM EWD ADVANCING COLD FRONT
GIVEN POTENTIAL FOR A CAP ASSOCIATED WITH THE EML. THE CAP SHOULD
GRADUALLY WEAKEN DURING THE DAY AS THE BOUNDARY LAYER WARMS AND AS
LARGE SCALE ASCENT AND HEIGHT FALLS INCREASE DOWNSTREAM FROM EWD
ADVANCING SHORTWAVE TROUGH. VERY LARGE LOW LEVEL HODOGRAPHS AND DEEP
SHEAR ASSOCIATED WITH THE UPPER TROUGH AND ITS ATTENDANT LOW LEVEL
JET WILL SUPPORT ORGANIZED STORMS INCLUDING SUPERCELLS. TORNADO
POTENTIAL WILL BE HIGHEST IF THE CAP WEAKENS ENOUGH FOR A FEW
DISCRETE STORMS TO DEVELOP WITHIN THE WARM SECTOR AHEAD OF THE
FRONT. OTHERWISE PRIMARY CONVECTIVE MODE WILL LIKELY EVOLVE TO
LINEAR...BUT WITH EMBEDDED LEWP AND SUPERCELLS STRUCTURES. DAMAGING
WIND...A FEW TORNADOES AND LARGE HAIL WILL BE POSSIBLE AS THIS
ACTIVITY ADVANCES EWD WITH LARGEST CONCENTRATION OF SEVERE WEATHER
EXPECTED IN MODERATE RISK AREA. SEVERE THREAT WILL CONTINUE BUT
GRADUALLY DECREASE AS THE LINE ADVANCES INTO THE MS VALLEY WHERE
INSTABILITY WILL BE MORE LIMITED.
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#738 Postby Extremeweatherguy » Fri Feb 15, 2008 4:32 am

Wow, a 45% hatched moderate risk zone right over SE Texas! This is going to be one dangerous weekend... :eek:
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Re: SE TX/SW LA - Severe weather Fri/Sat?

#739 Postby jasons2k » Fri Feb 15, 2008 8:29 am

From Jeff Lindner:

Potentially very dangerous severe weather event Saturday and Saturday night.

SPC has upgraded the entire region into a moderate risk for severe weather with a threat of long tracked supercells capable of producing strong tornadoes….see SPC graphics.

Deep upper trough slowing in the SW US this morning with a weak warm front along the coast and arctic cold front stalling inland over N and C TX. CRP, DRT, and LCH soundings show a very impressive warm layer above the surface (cap) and expect this to hold if not intensify during the day leading only to showers under this layer. After dark low level jet will rapidly increase to over 50kts in the 925-850mb layer and this will sling deeper moisture off the western Gulf into the region. W Gulf air mass is characterized by upper 60 to near 70 degree dewpoints and this will surge inland tonight. Lead short wave rounding the base of the upper trough will eject across C TX overnight and the lift combined with the increasing Gulf moisture should be enough to erode the cap and get things going. Expect multi cell storm clusters to develop and move NE across the region.

Saturday:

Dangerous weather day on tap.


Severe weather parameters looks downright nasty on Saturday will all severe modes likely. Low level jet continues to increase to near 60kts at 900mb during the day while upper trough begins its push eastward forcing surface low pressure in the region between Del Rio and Laredo. Entire area will be warm sectored with dewpoints in the upper 60’s to near 70 and strong southerly flow. Surface to 500mb winds are strongly veering and greatly increasing in speed leading to strong horizontal speed and direction wind shear. As surface low moves ENE across TX during the afternoon and evening strong surface convergence coupled with increasing upper air lift will release a very unstable air mass vertically into a highly sheared environment. By mid afternoon air mass will be very unstable with CAPES of 1500-2500 J/kg, TT over 55, PWS of 1.6-1.8”, and 0-6km shear of 70Kts. As surface low tracks from about San Antonio toward CLL expect surface winds to back slightly from the SSW to SSE and SE increasing the low level shear. Helecity values for 0-3km increase into the 450 m^2/s^2 range with nearly 90-110 degrees of turning of the air mass between the surface and 500mb. Additionally, 120 jet core will plow into SW and C TX at the same time adding even more wind energy and lift.


Expect warm sector showers and thunderstorms to be ongoing Saturday morning under impressive warm air advection regime. As air mass becomes very unstable and capping weakens Saturday afternoon expect scattered supercells to begin to develop as lift ahead of storm system increases. Given low level shear in place supercells will be rotating. I am concerned if discrete cells are able to develop Saturday afternoon…if they do the tornado threat is going to be high and a few of the tornadoes are going to be strong and potentially long tracked given EHI numbers of 2 this morning for Saturday PM…suggesting EF 2-3 tornado potential.

Area will really be under the gun starting about 300pm through about 300am Sunday as linear forcing approaches and sits off a squall line over C TX that roars eastward. Given tremendous wind energy expect widespread wind damage along this line. Supercells will develop ahead of the line Saturday evening and as the low level jet increases after dark…any cells rooted in the near surface air mass will likely produce tornadoes.

Storm motions will be increasing on Saturday and into Saturday night (35-45mph). This means warning lead times will be shrinking and residents may only have a few minutes of warning before adverse conditions impact your location. Additionally, the damaging wind and tornado threat appears highest after dark and when people will be sleeping which makes warning reception more difficult. We just witnessed last week the devastating effects systems like this can have.

Hydro:

Still expecting widespread heavy rains Saturday, but QPF looks lower now as storm motions will be faster and there is really no low level focus to train cells along. I am still concerned with the very high PW air and potential for HP supercells to prodcue 2-3 inches of rainfall in an hour or less….but the threat is too ill defined at any one location for much concern. Feel the best flood threat will come Saturday afternoon and night as grounds saturate and widespread thunderstorms/squall line moves across the region. Will go with basin average amounts of 1-3” with isolated amounts of 4-6” possible. Rainfall of this magnitude across the Tres Palacios, the San Bernard, and E/W Mustang Creeks will likely put them out of their banks. Just too hard to tell where the heaviest rains will be and which watersheds will be hit the hardest.

Tornado Safety

I strongly encourage residents to check weather information frequently on Saturday and remain fully aware of the developing situation. Multiple tornado watches are likely and there will be numerous warnings throughout this event. Know exactly what to do and where to go if your location is threaten by a tornado or straight line damaging winds. Since most locations do not have basements one of the safest locations is on the lowest floor or your house in an interior room with no windows…an interior bathroom or closet. There is no need to open any windows…your house will NOT explode from the pressure differences. Never try to out run a tornado in a vehicle. If caught in a vehicle seek a ditch or low spot or a sturdy building…it is not encouraged to hide under freeway overpasses as winds actually increase through these structures due to the wind funneling effect.
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#740 Postby jasons2k » Fri Feb 15, 2008 8:45 am

I've been looking at the charts this morning and don't like what I see. The trough rounds in Texas and goes from positivley tilted to negatively tilted rather fast right over Texas. EWG's maps above show it quite well. Textbook setup for a dangerous severe outbreak.
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