Flash Flood Warning 18, NWS Brownsville, TX

DEEP SOUTH TEXAS FORECAST DISCUSSION...CORRECTED CCF
NATIONAL WEATHER SERVICE BROWNSVILLE TX
210 PM CDT SUN SEP 9 2001

CURRENT VISIBLE SATELLITE LOOP IS SHOWING A THIN LINE OF WELL
DEVELOPED CUMULUS/TOWERING CU EXTENDING FROM JUST NORTH OF CORPUS
CHRISTI TO NEAR DEL RIO AT 09/1800Z.  IT IS DIFFICULT...AT THIS
TIME...TO DETERMINE WHETHER OR NOT THE LOW-LEVEL BOUNDARY FORCING
THE CU DEVELOPMENT IS AN OUTFLOW BOUNDARY OR THE TRUE SYNOPTIC COLD
FRONT.  ARCING NATURE OF THE CU LINE...AND LACK OF A DEWPOINT
GRADIENT PERPENDICULAR TO THE BOUNDARY WOULD ARGUE IN FAVOR OF
OUTFLOW.  LATEST MSAS ISALLOBARIC ANALYSIS INDICATES THAT STRONGEST
3-HOUR SURFACE PRESSURE RISES ARE CENTERED NEAR HOUSTON...WHICH
EXPLAINS THE FASTER SOUTHWARD PROPAGATION OF THE EASTERN PORTION OF
THIS LINE.  THE MID-LEVEL CYCLONIC CIRCULATION SEEN ON WV IMAGERY
SOUTH OF THE BIG BEND SHOULD CONTINUE MOVING NORTH AND WILL LIKELY
NOT HAVE A SIGNIFICANT IMPACT ON WEATHER IN SOUTH TEXAS.  KBRO
REFLECTIVITY DATA CURRENTLY SHOWS NUMEROUS SHOWERS AND THUNDERSTORMS
ORGANIZING ALONG THE BOUNDARY...AND THESE WILL IMPACT DEEP SOUTH
TEXAS LATER THIS AFTERNOON AND THIS EVENING.

OVERALL...AM NOT COMPLETELY SURE THAT THE HEAVY RAIN EVENT SCHEDULED
FOR MONDAY WILL MATERIALIZE AS PLANNED.  BOTH 09/12Z AVN AND 09/12Z
MESOETA ARE IN GOOD AGREEMENT...SO WILL GO WITH A BLEND FOR THIS
FORECAST.  SEVERAL THINGS CONCERN ME AT THIS POINT...THE MOST OF
WHICH IS THE MID/UPPER LEVEL RIDGING AND SUBSIDENCE THAT IS PROGGED
TO BUILD BACK OVER THE AREA BEGINNING EARLY MONDAY.  BOTH MODELS
SHOW DECENT 700 MB POSITIVE VERTICAL MOTION...BUT THERE ARE NO UPPER
LEVEL FEATURES TO SUPPORT THIS.  THE SOURCE OF LIFT MUST THEREFORE
COME FROM THE LOW-LEVEL BOUNDARY/COLD FRONT...WHICH MAY NOT EVEN
MAKE IT THIS FAR SOUTH...BASED ON CURRENT SURFACE PRESSURE TRENDS.
MOS NUMBERS STILL INDICATE HIGH POPS...BUT THESE ARE LIKELY BEING
INFLUENCED SUBSTANTIALLY BY THE CLIMATOLOGY COMPONENT OF THE
PREDICTION EQUATION.  EITHER WAY...THE BEST CHANCES FOR RAIN SHOULD
BE LIMITED TO MONDAY.  THUS...WILL LIMIT ALL POPS TO 40 THROUGH
MONDAY NIGHT...AND BEGIN A DECREASING TREND AFTER MONDAY NIGHT...AS
COLD FRONT REALLY BEGINS TO DISSIPATE.

IN THE EXTENDED PERIOD OF THURSDAY THROUGH MONDAY...MODEL GUIDANCE
IS POINTING TOWARD A RETURN TO MID/UPPER LEVEL RIDGING AND A MUCH
DRIER TROPOSPHERE OVER THE AREA.  A RETURN TO WARM TEMPS...MOSTLY
SUNNY DAYS...AND MOSTLY CLEAR NIGHTS CAN BE EXPECTED.

MARINE...SOUTHEAST WINDS HAVE DECREASED TO 8 KNOTS AT BUOY
020...WITH SEAS RESPONDING BY DECREASING TO 5 FEET. A SPECIAL MARINE
WARNING CONTINUES UNTIL 3:15 PM CDT...FOR A LINE OF STRONG
THUNDERSTORMS MOVING DOWN THE LOWER TEXAS COAST.  SHOWERS AND
THUNDERSTORMS WILL BE POSSIBLE THROUGH EARLY WEDNESDAY.

PRELIMINARY NUMBERS:
BRO TB 079/091 077/093 077 40/40/40/30/30
HRL TB 077/091 075/093 075 40/40/40/30/30
MFE TB 077/092 075/094 075 40/40/40/30/30
RGC TB 076/092 074/094 074 40/40/40/30/30
SPI TB 078/088 076/089 076 40/40/40/30/30

SYNOPTIC...DD (65) / AVIATION-MARINE...BHM (54) / MESO...SM

INTERNET ADDRESS...WWW.SRH.NOAA.GOV/BRO

.BRO...SCA GMZ150-155-170-175.