MESOSCALE PRECIPITATION DISCUSSION 0600...CORRECTION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
618 PM EDT THU OCT 22 2015
 
AREAS AFFECTED...SOUTHERN TX 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 222213Z - 230213Z
 
SUMMARY...A CONVECTIVE COMPLEX WITH COOLING CLOUD TOPS IS LEADING
TO HIGH HOURLY RAIN RATES.  FLASH FLOODING IS POSSIBLE IN URBAN
AREAS BETWEEN BROWNSVILLE AND CORPUS CHRISTI.

DISCUSSION...A SMALL THUNDERSTORM COMPLEX RECENTLY CONGEALED
ACROSS SOUTHERNMOST TX, AN OFFSHOOT OF ACTIVITY WHICH HAD BEEN
HOVERING OFFSHORE FOR MORE THAN 24 HOURS.  HOURLY RAIN RATES
RECENTLY REACHED 3.5", WITH TOTALS NEAR 5", PER RADAR ESTIMATES. 
INFLOW AT 850 HPA IS 25-30 KTS, SLIGHTLY HIGHER THAN THE MEAN 850
HPA WIND.  PRECIPITABLE WATER VALUES OF 2-2.4" LIE ACROSS THE
REGION, 2.5 SIGMAS ABOVE THE MEAN FOR LATE OCTOBER.  CIN LIES
ACROSS THE REGION, WITH MUCAPES OF 2000-4000 J/KG JUST OFFSHORE
SOUTHERN TX.

NONE OF THE CAM GUIDANCE HAS MORE THAN 0.1" OF RAINFALL IN THIS
REGION, WITH A MORE DISTANT SIGNAL FOR LOCAL 2-3" AMOUNTS
SOMEWHERE ACROSS THE TX COASTAL PLAIN.  HOWEVER, THE
GALVEZ-DAVISON INDEX BASED ON THE 12Z GFS HAS A SIGNIFICANT
SIGNAL, WITH VALUES OF 40+ ACROSS SOUTHERNMOST TX, IMPLYING
CONVECTION SHOULD BECOME MORE NUMEROUS GIVEN THE AMOUNT OF
MOISTURE AND INSTABILITY.  THUNDERSTORMS ACROSS THE REGION HAD
BEEN GENERALLY EXPANDING NORTHWEST AT 10 KTS, THOUGH CELLS AS OF
LATE APPEAR TO HAVE STOPPED THEIR WESTWARD PROGRESS, LIKELY DUE TO
GREATER ORGANIZATION.  ANOTHER POSSIBILITY IS THAT THE BEST
BOUNDARY LAYER MOISTURE CONVERGENCE IS STUCK NEAR/JUST INLAND OF
THE COAST, WHICH WAS OCCASIONALLY SEEN IN THE 20-22Z RAP RUNS. 
ORGANIZED CONVECTION WILL ATTEMPT TO PEEL OFF TO THE EAST FROM
TIME TO TIME, WHICH COULD CONTINUE CELL MERGERS, WHILE CELL
TRAINING OCCASIONALLY OCCURS DOWNWIND OF THE INSTABILITY POOL. 
HOURLY RAIN RATES UP TO 3", AND LOCAL AMOUNTS OF TO 8", ARE
CONSIDERED POSSIBLE.  WILL USE A FOUR HOUR TIME FRAME AND SEE HOW
THIS UNEXPECTED HEAVY RAINFALL EVENT UNFOLDS.  FLASH FLOODING IS
POSSIBLE, ESPECIALLY WITHIN URBAN AREAS.

ROTH

ATTN...WFO...BRO...CRP...

ATTN...RFC...WGRFC...

LAT...LON   28329745 28119686 27339723 26779725 25879709 
            25729744 25909798 26339899 27449856