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

[Extremeweatherguy]

The rain today has been crazy! I was not expecting this at all. Based on the radar estimates, my area has seen somewhere between 3.5-5" today...and there is still a little bit more to come.

[jasons2k]

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
325 PM CDT MON MAY 5 2008

.DISCUSSION...
QUITE A DAY ACROSS THE COUNTY WARNING AREA. A NARROW AXIS OF HEAVY
RAIN THIS MORNING PRODUCED A SWATH OF 6 TO 8 INCHES OF RAIN FROM
WASHINGTON COUNTY ACROSS SOUTHERN GRIMES/NORTHERN WALLER TO
NORTHERN HARRIS COUNTIES. SOME SPOTTER REPORTS SHOW 8 INCHES NEAR
INDEPENDENCE...ABOUT 6 INCHES IN NORTHERN WALLER AND 6 TO 7
INCHES IN NORTHERN HARRIS. THE RAIN AREA IS SHIFTING NORTH AND
WILL LIKELY PERSIST INTO THE EVENING BEFORE DISSIPATING AROUND
03Z. FURTHER SOUTH...DAYTIME HEATING IS TRIGGERING ADDITIONAL
SHOWERS. PRECIP CONTINUES TO FOCUS ON A WELL DEFINED OUTFLOW
BOUNDARY EXTENDING FROM BAY CITY TO TEMPLE. RAINFALL HAS
DIMINISHED IN INTENSITY AND FEEL THE ATMOSPHERE WILL NEED A
LITTLE TIME TO RECHARGE SO WILL END THE FLOOD WATCH THIS EVENING.

ANOTHER S/WV IS EXPECTED TO APPROACH THE AREA OVERNIGHT. NOT SURE
HOW WORKED OVER THE ATMOSPHERE WILL BE BUT FEEL IT IS BEST TO
CARRY SOME POPS OVERNIGHT. GFS LOOKS OVERDONE WITH THE S/WV AND
WILL LEAN TOWARD THE ECMWF. UPPER LEVEL DIVERGENCE IS STRONGER
EARLY TUESDAY BUT MOISTURE LEVELS ARE LOWER THAN TODAY. MOISTURE
SHOULD REMAIN SUFFICIENT FOR AT LEAST SCATTERED SHOWERS ON TUESDAY.

ANOTHER UPPER LEVEL TROUGH WILL SWING ACROSS THE SOUTHERN PLAINS
ON WEDNESDAY. THIS SYSTEM LOOKS TO BE TRACKING A LITTLE FURTHER
SOUTH WITH EACH MODEL RUN. FORECAST SOUNDINGS ON WEDNESDAY
AFTERNOON SHOW CAPPING IS LOW OVER THE NORTH AND BREAKABLE OVER
THE CENTRAL ZONES. WILL CARRY CHANCE POPS FOR WEDNESDAY. SPC HAS
THE NORTHERN HALF OF THE REGION OUTLOOKED IN SLIGHT RISK. CAPE
DOESN`T LOOK TOO IMPRESSIVE BUT THERE IS PLENTY OF SHEAR.

AFTER WEDNESDAY...AN EXPANDING 500 MB RIDGE WILL MOVE INTO THE
REGION FROM THE EAST. THIS SYSTEM WILL SHUT DOWN RAIN CHANCES AND
BEGIN A PERIOD OF VERY WARM TEMPERATURES. HIGH TEMPS THU-SAT WILL
WARM INTO THE LOWER 90S.

[southerngale]

It was raining when I woke up early this morning and it hasn't stopped all day. While some of it has been pretty heavy and some of it has been light, it's mostly been a steady, moderate rain. I had quite a bit of thunder earlier today, but just rain for the past several hours. While it's rained a lot, I haven't gotten as much here as Jason's area! Dang, Jason... want to borrow my ark?



AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LAKE CHARLES LA
359 PM CDT MON MAY 5 2008

.SYNOPSIS...
AN AREA OF RAIN AND EMBEDDED THUNDERSTORMS EXTENDS FROM N CNTRL TX
TO SE TX AND EXTREME SW LA. THIS AREA CONTINUES TO MOVE SLOWLY
EAST. RADAR ESTIMATES AND OBSERVATIONS FROM SE TX DRAINAGE
DISTRICT 6 GAGES INDICATE 2.5 TO 3 INCHES OF RAIN HAS FALLEN
ACROSS WESTERN PORTIONS OF JEFFERSON AND HARDIN COUNTIES SINCE
THIS MORNING...A WELCOME RELIEF FROM THE RECENTLY DRY CONDITIONS
ACROSS THIS AREA.

THIS AREA OF PRECIPITATION IS THE RESULT OF AN UPPER LEVEL IMPULSE
TRAVERSING THE GENERALLY ZONAL FLOW ALOFT. AT THE SFC...A WEAK
FRONTAL BDRY IS SITUATED FM CNTRL TX SE TOWARD THE NW GULF...WHILE A
LARGE AREA OF HIGH PRESSURE CENTERED OVER NRN MS IS RIDGING ACROSS
THE FCST AREA.

[jasons2k]

I've had 5 and 1/2 inches and counting! You have oars too?

[southerngale]

Of course!

It's 59F right now - on May 5th - late afternoon!

[Extremeweatherguy]

Of course!

It's 59F right now - on May 5th - late afternoon!

Yeah, the rain has definitely kept things on the "cool" (but muggy) side today. Officially, the high temperature for May 5th, 2008 at Bush Intercontinental Airport in Houston will be 72-degrees...which occurred right after midnight this morning. Since sunrise though, we have not gotten out of the 60s. In fact, there was even a point during the heavy rain earlier today that I could see my breath (the air temperature was 62F at the time). It was somewhat exciting and unusual for May.

[Extremeweatherguy]

Hmm. This is an interesting quote from the evening Houston AFD...

WEDNESDAY LOOKS TO BE AN
INTERESTING WEATHER DAY WITH A STRONG LLJ/2000+ CAPE/PREFRONTAL
TROUGH/DRYLINE/SRH 190-335 M2/S2...AS PREVIOUS FORECASTER
DISCUSSED THE SQUALL LINE POTENTIAL LOOKS GOOD AND POSSIBLY SOME
SUPERCELLS.

[Ptarmigan]

I notice some flare ups west of Del Rio. I wonder if it will effect us?

[vbhoutex]

I notice some flare ups west of Del Rio. I wonder if it will effect us?

Quite possibly some am rains.

[jasons2k]

Morning update from Jeff Lindner:

Impressive rainfall event yesterday across the N ½ of the region.

12 hour rainfall totals averaged 4-8 inches along a narrow band from S of College Station to near The Woodlands. Totals from the Harris County Flood ALERT System indicated 5-7 inches along the middle portion of Spring Creek and 3-5 inches over Cypress Creek. A maximum total of 7.79 was recorded at ALERT station 1070 at SH 249 and Spring Creek. There was also one report of 8.14 inches from an observer in Independence in Washington Co. This event was almost identical to the flooding in E TX in April when 10-12 inches fell in about 12 hours over parts of Jasper County. Training thunderstorms in a tropical atmosphere will get you every time and the totals can be big in a small period…something to remember as we move into the warm season months and our air mass transitions toward a semi-tropical one!

BUSH IAH: 3.47--- 24 hour rainfall record breaking the old record of 1.89 in 1993
Conroe: 2.31
Tomball: 3.20

Significant rises did occur along the lower end of Cypress Creek and the W fork of the San Jacinto River as well as Willow and Spring creeks. Per RFC forecast the W fork of the San Jacinto River at Humble will be rising above action stage and cresting below flood stage. Narrow band of excessive rainfall fell over the middle Brazos basin in Washington and Grimes counties…however the small spatial distribution has not resulted in a major rise at Hempstead. Minus the W fork of the San Jacinto and middle Spring Creek all watersheds are receding this morning.

Forecast:

Large upper trough over the SW US sending impulse after impulse across TX in noisy SW flow aloft. Current MCS ongoing over N TX with second cluster over S TX…very similar to 24 hours ago without development over SE TX. Local air mass is somewhat drier this morning when compared to yesterday with dewpoints in the lower 60’s and is still in recovery mode. Will need to keep close watch on any outflow boundaries spreading SE from N TX or NE from S TX into the area this afternoon as they may be able to spark a few thunderstorms.

Main upper system ejects into W TX tonight and moves toward the Red River on Wed with surface dry line advancing across C TX. Low level jet cranks up tonight as pressures fall over W TX and deep tropical moisture will surge inland. Strong heating and dynamics come to bear across C TX dry line Wednesday and expect rapid deep severe convection to develop during the afternoon hours along the dry line. Track of the upper trough grazes our area with favorable lift and dynamics…however meso scale forcing may indeed take over given potential for MCS/squall line and favorable Gulf inflow pattern. A few storms could be severe with hail and damaging winds….although the main threat appears to be heavy to excessive rainfall. Feel the best area to see thunderstorms will be along and N of I-10 where capping will be least…with chances only around 20-30% along the coast.

After Wednesday large sub-tropical ridge builds over the region drying the air mass and really cranking the heat. Will temper afternoon highs at IAH and in the area that had heavy rains yesterday as some of the solar energy will go toward ground evaporation. Areas that did not see much rain yesterday will likely see 90 on Thursday and the lower 90’s Friday through the weekend with heat index values at or above 100.

Note: As is so common in these parts….the rains yesterday completely erased the rain deficit at IAH which was running about 2.0 inches below normal. Now we have a rainfall surplus for 2008 of a little of 1.25 inches.

[srainhoutx]

HGX tends to agree, Jason...


FXUS64 KHGX 061509
AFDHGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
1009 AM CDT TUE MAY 6 2008

.DISCUSSION...
AT 14Z...A PLETHORA OF BOUNDARIES WERE NOTED. IT APPEARS THAT A
WEAK WARM FRONT STILL LINGERS OVER PARTS OF SOUTHEAST TEXAS. THIS
BOUNDARY SEPARATES LOWER 60S DEW POINTS FROM LOWER 70S. NUMEROUS
OUTFLOW BOUNDARIES ALSO WERE NOTED FROM CENTRAL AND SOUTH TEXAS
INTO SOUTHEAST TEXAS. 250 MB WINDS ARE DIVERGENT TODAY AND
MOISTURE IS STILL RATHER PLENTIFUL. FORECAST SOUNDINGS SHOW A
BREAKABLE CAP SO IF CLOUDS BEGIN TO ERODE...EVEN MODEST HEATING
SHOULD HELP TO TRIGGER SHOWERS AND THUNDERSTORMS. WILL RAISE POPS
INTO CHANCE THIS AFTERNOON. 12Z NAM IS AGGRESSIVE WITH RAIN
CHANCES THIS AFTERNOON AND MAY RAISE POPS FURTHER IF SHORT TERM
MODELS SUPPORT THE LATEST NAM SOLUTION. TEMP/WINDS LOOK GOOD...SO
NOT PLANNING ANY OTHER CHANGES. 43

[jasons2k]

Update from Jeff at 12:56:

Air mass starting to destabilize early this afternoon.

Visible satellite images and radar shows numerous surface boundaries remain in place across SE TX with most noted being the old warm front which extends from High Island to IAH to CLL. Breaks have developed in the overcast deck over our SW zones and within the past hours echoes have developed in the radar sweeps over Wharton and Fort Bend counties. CRP AM sounding came in uncapped and unstable…so given a little more heating and cooking of the numerous low level boundaries in place may set things off. Will also be getting a little lift as S TX short wave moves across the region S of I-10 as noted by scattered showers over Matagorda and Jackson counties. NAM and other shorter term models are very aggressive in developing widespread rainfall this afternoon and are going with high rain chances…not sure they will be right given the current lack of development…however we may see more than the current 30-40% coverage. Will need to keep a close watch on radar trends over the next 2-3 hours.

Good news is that increasing southerly flow as pressures fall over W TX should help wash out the boundaries over the area by late afternoon unless organized convection is able to develop and create new ones.

[KatDaddy]

I should have posted this over in the tropic forum however most locals browse this thread. Both of these seminars are in Houston next Monday afternoon and Tuesday morning.

Just Registered for the ImpactWeather Hurricane Seminar

I look forward to meeting WXman57 and posters from the CH11 and S2K board.

Also registered for the Accu-Weather Hurricane Seminar next Monday downtown.

[KWT]

Oh sounds cool I would love to hear what they say, esp the accuweather hurricane seminar.

[Ed Mahmoud]

18Z WRF coming in similar to 12Z models, with most of the rain tomorrow confined to the far Northern suburbs of Houston.


Thank goodness for the big rain yesterday.

[jasons2k]

I had 5.58" yesterday.

[Ed Mahmoud]

I had 5.58" yesterday.

Judging by radar rainfall accumulations and DWH and IAH, we got between 3 and 3.5 inches.



Which is good.

But if the cap can be overcome all the way to I-10 in HOU tomorrow afternoon, I won't complain.

[Ed Mahmoud]

I had 5.58" yesterday.

Judging by radar rainfall accumulations and DWH and IAH, we got between 3 and 3.5 inches.



Which is good.

But if the cap can be overcome all the way to I-10 in HOU tomorrow afternoon, I won't complain.

NWS isn't excited about rain chances South of Conroe...

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
641 PM CDT TUE MAY 6 2008

.AVIATION...
CEILINGS SHOULD LIFT SOME THIS EVENING AS A WEAK SHORTWAVE TROUGH
EXITS THE REGION. SUBSIDENCE ON THE BACK SIDE OF THE SHORTWAVE
SHOULD SUPPRESS SOME CLOUD DEVELOPMENT TONIGHT. BOTH NAM/GFS PICK
UP ON SOME DRIER AIR COMING OFF THE GULF IN THE 925/850MB LAYER.
THE BOUNDARY LAYER DOES SATURATE AFTER 06Z SO WILL BRING IN SOME
LOW CIGS AROUND 10Z FOR MUCH OF SE TX. CLOUDS SHOULD SCATTER OUT
BY THE MORNING. A STRONG LLJ IS ALSO EXPECTED BUT WILL HOLD OFF
ON MENTION OF LLWS UNLESS VAD WINDS FROM THE 88D SUGGEST
OTHERWISE. LLJ MAY PICK UP TO 40KTS WHICH WILL BE CLOSE TO LLWS
CRITERIA. OTHERWISE...CONVECTION TOMORROW AFTERNOON WILL BE THE
MAIN CONCERN. BOTH NAM/GFS SUGGEST CONVECTION AS FAR SOUTH AS
CXO SO WILL AT LEAST TEMPO TSRA FRO KCLL...KUTS AND KCXO. KIAH
WILL GET A MENTION OF CB BUT THINK THE CAP MAY BE STRONG ENOUGH
TO HOLD OFF CONVECTION THAT FAR SOUTH. EVEN KCXO WILL BE BORDER
LINE. SFC WINDS ALSO INCREASE TO NEAR 20KTS SUSTAINED AS THE
PRESSURE GRADIENT TIGHTENS UP WITH SFC LOW OVER N TX. GUSTS WILL
BE IN THE 25-30KT RANGE MAINLY AFTER 18Z WITH STRONG MIXING.

[Extremeweatherguy]

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
948 PM CDT TUE MAY 6 2008

.UPDATE...
SKIES CLEARED IN THE WAKE OF THE S/W BUT HIGH CLOUDS ARE SPREADING
IN FROM THE WEST AND LOWER (2000 FT-ISH) CLOUDS BEGINNING TO DOT
THE COASTAL AND EASTERN COUNTIES. EVENING SOUNDINGS AND MODEL
SOUNDINGS APPEAR TO INDICATE THAT PRECIP CHANCES LOOK TO BE VERY
SLIM OVER MOST OF THE AREA. HAVE PARED BACK POPS OVER ALL BUT THE
FAR NORTHWESTERN ZONES TOWARD MORNING WHERE PERHAPS ENOUGH LIFT
COULD COME TO BEAR TO POP A FEW SHOWERS OR THUNDERSTORMS. AS THE
CLOUDS MOVE IN EXPECT THE TEMPERATURE FALL TO LEVEL OFF SO HAVE
NUDGED UP THE MINS A DEGREE OR TWO. THE LLJ SHOULD CRANK UP
TONIGHT WITH WINDS AT 850 APPROACHING 50 KNOTS OVER HARRIS COUNTY
AND 60 KNOTS OVER THE WESTERN ZONES BY MORNING. PARAMETERS LOOK TO
BE COMING TOGETHER FOR SEVERE WEATHER IN THE NW/NRN ZONES DURING
THE AFTERNOON. THE QUESTION IS HOW MUCH CAP ARE WE GOING TO
HAVE...AS HAS BEEN THE CASE/QUESTION RECENTLY. ATTM EXPECTING THE
CAP TO HOLD OVER THE SOUTHERN HALF OF THE CWA BUT AREAS NORTHWARD
THE CAP SHOULD BE BREAKABLE. CAPE OF 800-2100 J/KG...LI -2-4...3KM
SRH 150-300 M2/S2 DURING THE AFTERNOON HOURS AS THE DRYLINE MOVES
INTO THE WESTERN CWA. THE DRYLINE DOESN`T LOOK TO MOVE MUCH INTO
THE CWA THOUGH SO STORMS COULD HAVE A BRIEF WINDOW TO GO SEVERE AS
THEY MOVE OFF OF IT. WILL GO AHEAD AND ADD MENTION OF SEVERE TO
THE GRIDS FOR THE AFTERNOON HOURS.

JUST FOR AMUSEMENT WAS LOOKING AT THE MOISTURE CONTENT...THE
MODEL PW IS AT NEARLY THE SECOND STANDARD DEV FOR THE MONTH OF MAY
SO WILL ALSO NEED TO WATCH FOR THE POTENTIAL OF HEAVY
RAINFALL...THOUGH IT MAY BE NARROW SWATHS/FAR SMALLER AREAL COVERAGE
THAN YESTERDAYS BIG RAINS. MODELS CONTINUE TO POINT TO WIDESPREAD
90+ AFTERNOONS COMING OUR WAY THU-SAT...HEAT INDICIES OF 94-98 ON
SATURDAY DURING THE OUTDOOR ACTIVITIES...SO STAY HYDRATED.

MOST UPDATES ALREADY OUT BUT WILL UPDATE THE GRAPHICAST IMAGES
SHORTLY.

[Ed Mahmoud]

12Z sounding shows cap of forged steel, yay, high pressure water molded titanium at Corpus Christi.




Lake Charles has a much weaker cap. The convective T listed is 100ºF, but I think that is a bug, as eyeballing that, upper 20sC should be sufficient.


In the last few events, when CRP showed a solid cap, and LCH showed a breakable cap, the cap generally held I-10 area and Southward around HOU, so, if I had to guess, the model forecasts of rain from Conroe area Northward with HOU high and dry are probably in the ballpark.