SE TX/SW LA Discussion Thread - Heavy Rainfall Threat

[Ptarmigan]

Not sure when the time period for the main event over SE TX will be. Period from Mon-Wed looks very wet. Comparison event appearing as July 2002 floods in C TX with multiple rounds over several days creating river flooding.

Locally concern for high hourly rainfall rates which can quickly do us in over Harris County. Testament of potential over N Waller Co this afternoon where 4-6 inches fell in a few hours in a much drier air mass than we will face by Monday. Headwaters of Spring Creek will likely exceed banks late tonight with downstream rises at SH 249 and I-45 Saturday into Sunday. Luckily the headwaters are flashy and will go down quickly (likely) by early Saturday AM.

Those rains in Harris County were more isolated and it happened with a drier air mass. I think there will be widespread heavy rain in Southeast Texas starting Sunday night into Wednesday. Last Memorial Day was a wet one too with heavy rain and flooding. History is repeating itself again. I wold not be surprised if Central Texas by Meorial Day got up to 30 to 35 inches of rain and 25 inches of rain in Southeast Texas by Thursday.

[vbhoutex]

Not sure when the time period for the main event over SE TX will be. Period from Mon-Wed looks very wet. Comparison event appearing as July 2002 floods in C TX with multiple rounds over several days creating river flooding.

Locally concern for high hourly rainfall rates which can quickly do us in over Harris County. Testament of potential over N Waller Co this afternoon where 4-6 inches fell in a few hours in a much drier air mass than we will face by Monday. Headwaters of Spring Creek will likely exceed banks late tonight with downstream rises at SH 249 and I-45 Saturday into Sunday. Luckily the headwaters are flashy and will go down quickly (likely) by early Saturday AM.

Those rains in Harris County were more isolated and it happened with a drier air mass. I think there will be widespread heavy rain in Southeast Texas starting Sunday night into Wednesday. Last Memorial Day was a wet one too with heavy rain and flooding. History is repeating itself again. I wold not be surprised if Central Texas by Meorial Day got up to 30 to 35 inches of rain and 25 inches of rain in Southeast Texas by Thursday.

What are you basing your predictions on?

[Ptarmigan]

What are you basing your predictions on?

Whenever, the NWS/NOAA issues rainfall amount prediction, I tend to double it (Below 10 inches) or add it by 5 to 10. Currently, I am currently basing it on rainfall amount that has fallen.

[Extremeweatherguy]

NWS has upped rain chances today to 50%.

[jasons2k]

There a big line west of here this AM moving slowly east

[Extremeweatherguy]

[Johnny]

Thanks for the heads up on the rain heading this way. This is the first place I came to this morning and was surprised to see that!

[Extremeweatherguy]

looks like a low is spinning up WSW of Sealy right now.

[JenBayles]

Good grief! Those storms have been training for hours, and not much sign of them moving eastward.

[Ptarmigan]

It rained early this morning. No thunder, just heavy rain. There is a line of slow moving storms west of us and it is slowly heading towards us. I expect heavy rain later today.

[KatDaddy]

Hey EWG notice that heavy training over Wharton and Matagorda Counties progressing slowly eastward. I dont see any reason why this system will not affect at least the central counties in another 4 hours or so unless the southern part of the line stops reforming.

[srainhoutx]

Hey EWG notice that heavy training over Wharton and Matagorda Counties progressing slowly eastward. I dont see any reason why this system will not affect at least the central counties in another 4 hours or so unless the southern part of the line stops reforming.

my thoughts exactly

[Extremeweatherguy]

Hey EWG notice that heavy training over Wharton and Matagorda Counties progressing slowly eastward. I dont see any reason why this system will not affect at least the central counties in another 4 hours or so unless the southern part of the line stops reforming.

I agree. The whole system has been slowly shifting eastward all morning, and I see no reason why central zones will not be under the gun next. Could be an interesting (and wet) afternoon...

[JenBayles]

KD or EWG, or anyone else: can someone explain to me why these north/south rain lines that have formed for the past few days just don't want to move east very quickly? I have a declining mind and want to know...

[JenBayles]

SEVERE WEATHER STATEMENT
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
1120 AM CDT SAT MAY 26 2007

TXC089-261645-
/O.CON.KHGX.TO.W.0013.000000T0000Z-070526T1645Z/
COLORADO TX-
1120 AM CDT SAT MAY 26 2007

...A TORNADO WARNING CONTINUES FOR COLORADO COUNTY UNTIL 1145 AM
CDT...

AT 1117 AM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
THUNDERSTORM CAPABLE OF PRODUCING A TORNADO 5 MILES SOUTHWEST OF
FRELSBURG...MOVING NORTHEAST AT 15 MPH. THE CIRCULATION WITH THE
STORM HAS WEAKENED SOMEWHAT BUT IT STILL HAS TORNADIC POTENTIAL.

* LOCATIONS IMPACTED INCLUDE...
FRELSBURG...

PLEASE REPORT SEVERE WEATHER TO THE COUNTY SHERIFF...LOCAL POLICE...
OR DEPARTMENT OF PUBLIC SAFETY. THEY WILL RELAY YOUR REPORT TO THE
NATIONAL WEATHER SERVICE.

[JenBayles]

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
1043 AM CDT SAT MAY 26 2007

.DISCUSSION...
SLOW MOVING BAND OF TSRA AFFECTING THE WESTERN THIRD OF SE TX THIS
MORNING. STRONGEST ACTIVITY CONTINUES IN VICINITY OF MESOLOW OVER
COLORADO COUNTY WHERE RAINFALL AMOUNTS OF 1 TO 2 INCHES AN HOUR
HAVE BEEN COMMON. IN ADDITION...TSRA ASSOCIATED WITH MESOLOW HAVE
SHOWN EVIDENCE OF ROTATION IN THE LAST 30 MINS OR SO. OUTSIDE OF
THE STORMS OVER COLORADO COUNTY...VERY LITTLE LIGHTNING OCCURRING
AND RAINFALL RATES ARE GENERALLY RUNNING LESS THAN 1 INCH AN HOUR.
WILL GO WITH CATEGORICAL POPS FOR WESTERN THIRD THIS AFTN.
ANTICIPATING RAINFALL AMOUNTS IN THIS AREA BY EARLY EVENING OF
1-1.5 INCHES...ISOLATED 3-4 INCHES. FURTHER EAST...SCATTERED TSRA
EXPECTED TO DEVELOP WITH CONVECTIVE TEMPS ONLY IN THE UPPER 70S
AND PWS OF 1.8 INCHES+. WILL KEEP 30-50 POPS GOING IN THIS AREA.
DUE TO SPOTTY NATURE OF HEAVY RAINFALL...WILL HOLD OFF ON FFA FOR
NOW BUT WILL BE CONSIDERING A FFA FOR THE WESTERN THIRD OF SE TX
IN THE AFTERNOON PACKAGE.

[KatDaddy]

The ridging over the SE US has blocked disturbances from moving eastward This blocking has created deep moisture convergence across Central TX over the last few days. Basically a squeeze play is occurring across Texas. Jeff or Wxman 57 can give more detailed specifics.

[JenBayles]

Nice summation here I just picked up from a local TV station met posting:

From NESDIS:

Event...very slow moving line of convection continues heavy rain threat


..Satellite analysis and trends...3 hour automated satellite estimates generally range from 1.5-2.5" along entire length of line stretching from coastal se TX to hill/ Navarro counties. However localized totals to 3" and possibly higher are likely as automated technique focuses more on cloud tops and underestimates the efficiency of the warm cloud layer depth (around 4km) as seen on 12z raob soundings. Currently the area which stands out the best in ir loops is the region centered around Colorado county where meso-low has formed per radar loop and recent swomcd. As pointed out earlier, while cloud tops may not be totally indicative of rainfall intensity, in this case they do point to small scale spot of good lift with some overshooting tops detected in corresponding visible imagery. The very slow eastward movement to this meso-low will lead to intense rainfall rates exceeding 2"/hr for portions of Colorado/ Washington/ Austin counties for at least the next 30-60 minutes. To the south, convection continues to feed northward from the Gulf of Mexico with heavy rain producing cells affecting Jackson/ Wharton/ Matagorda counties. Concern still exists for this southern part of the line to hang up and/or fill in, in response to disturbances located farther to the west such as the one moving north of Del Rio. Currently monitoring some new development from around Corpus Christi to east of Victoria as a possible sign that this could occur. 12z soundings from spots approximately along the line (Dallas and Corpus Christi) show very little shear in the lower levels with nearly unidirectional southerly flow so needless to say even if line continues to move to the east, it will do so only very slowly..

[KatDaddy]

Posted by Dan Dan Meador over on the KHOU Channel 11 board

From NESDIS:

Event...very slow moving line of convection continues heavy rain threat


..Satellite analysis and trends...3 hour automated satellite estimates generally range from 1.5-2.5" along entire length of line stretching from coastal se TX to hill/ Navarro counties. However localized totals to 3" and possibly higher are likely as automated technique focuses more on cloud tops and underestimates the efficiency of the warm cloud layer depth (around 4km) as seen on 12z raob soundings. Currently the area which stands out the best in ir loops is the region centered around Colorado county where meso-low has formed per radar loop and recent swomcd. As pointed out earlier, while cloud tops may not be totally indicative of rainfall intensity, in this case they do point to small scale spot of good lift with some overshooting tops detected in corresponding visible imagery. The very slow eastward movement to this meso-low will lead to intense rainfall rates exceeding 2"/hr for portions of Colorado/ Washington/ Austin counties for at least the next 30-60 minutes. To the south, convection continues to feed northward from the Gulf of Mexico with heavy rain producing cells affecting Jackson/ Wharton/ Matagorda counties. Concern still exists for this southern part of the line to hang up and/or fill in, in response to disturbances located farther to the west such as the one moving north of Del Rio. Currently monitoring some new development from around Corpus Christi to east of Victoria as a possible sign that this could occur. 12z soundings from spots approximately along the line (Dallas and Corpus Christi) show very little shear in the lower levels with nearly unidirectional southerly flow so needless to say even if line continues to move to the east, it will do so only very slowly..
_________________
Dan Meador
KHOU Weather

[KatDaddy]

LOL Jen!!!!!!!