MESOSCALE PRECIPITATION DISCUSSION 0601
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
945 PM EDT THU OCT 22 2015
 
AREAS AFFECTED...DEEP SOUTH TX 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 230144Z - 230544Z
 
SUMMARY...A SMALL THUNDERSTORM COMPLEX CONTINUES TO MEANDER ACROSS
WILLACY COUNTY, MAINTAINING HIGH RAINFALL RATES OF 3" AN HOUR. 
FLASH FLOODING REMAINS POSSIBLE IN ITS VICINITY.

DISCUSSION...A CONVERGENCE BOUNDARY/COASTAL FRONT ACROSS
SOUTHERNMOST TX CONTINUES TO ACT AS A FOCUS FOR A SMALL
THUNDERSTORM COMPLEX WITH HIGH RAINFALL RATES, WHICH HAVE AVERAGED
3" AN HOUR SINCE 2130Z.  THE COMPLEX'S SIZE AND ITS CLOUD TOP
TEMPERATURES HAVE WAVERED A BIT OVER THE PAST FEW HOURS, BUT THE
SYSTEM HAS NOT DISSIPATED.    INFLOW AT 850 HPA REMAINS
SOUTH-SOUTHEAST AT 25-30 KTS, NEAR THE MAGNITUDE OF THE 850-400
HPA MEAN WIND WHICH IS LEADING TO PRECIPITATION EFFICIENCY.  THE
LOW-LEVEL INFLOW NEARLY BALANCES THE CONVECTIVE PROPAGATION, WHICH
WOULD OTHERWISE TRY TO TAKE IT EAST TO SOUTHEAST AT 25 KTS. 
THOUGH THE COMPLEX HAS BEEN CONFINED TO WILLACY COUNTY AS OF LATE,
IT IS BEGINNING TO INVADE SOUTHERN KENEDY COUNTY, DISPLAYING AN
UNEVEN NORTHWARD DRIFT DUE TO THE ABOVE COMPETING FACTORS.  CIN
REMAINS ACROSS THE REGION, THOUGH WITH MUCAPES OF 2000-4000 J/KG
UPSTREAM ACROSS THE WESTERN GULF OF MEXICO, CONVECTION HAS BEEN
ONLY SLIGHTLY ELEVATED OVER THE BOUNDARY.  DIVERGENCE ALOFT
REMAINS SIGNIFICANT NEAR HURRICANE PATRICIA'S OUTFLOW JET, WHICH
HAS ALSO BROUGHT IN MOISTURE ALOFT.  THE PASSING BY OF A SHORTWAVE
MOVING UP THE TX COAST HAS NOT LED TO ANY APPARENT CHANGE TO THE
DIVERGENCE ALOFT.  PRECIPITABLE WATER VALUES IN THE AREA REMAIN
BETWEEN 2.2-2.4", AROUND 2.5 SIGMAS ABOVE THE MEAN FOR LATE
OCTOBER.

THERE HAS BEEN NO CHANGE IN THE SYNOPTIC SETUP, WHICH INCREASES
THE CONCERN THAT THIS COMPLEX COULD LIVE ON FOR QUITE SOME TIME. 
RECENT RAP RUNS SHOW STRENGTHENING BOUNDARY LAYER MOISTURE
CONVERGENCE JUST INLAND OF THE COAST, PARTIALLY DUE TO DECOUPLING
INLAND AND ALSO DUE TO RAIN COOLED AIR TRYING THE REINFORCE THE
BOUNDARY, WHICH COULD MIGRATE SLIGHTLY INLAND WITH TIME. 
INCREASING THE UNCERTAINTY HERE IS THAT THE CAM GUIDANCE REMAINS
UNIMPRESSED, WITH RECENT HRRR RUNS FINALLY CAPTURING IT BRIEFLY,
BEFORE KILLING IT OFF QUICKLY.  THE AVAILABLE MOISTURE CONTINUES
TO SUPPORT HOURLY RAIN RATES TO 3", WHICH THUS FAR HAS LED TO
LOCAL MAXIMA IN THE 6-10" RANGE PER DUAL POL RADAR ESTIMATES. 
THIS DEGREE OF RAINFALL WOULD BE SIGNIFICANT IN THE FEW URBAN
AREAS WHICH EXIST BETWEEN BROWNSVILLE AND CORPUS CHRISTI TX. 
FLASH FLOODING REMAINS POSSIBLE WITHIN THIS AREA.

ROTH

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

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

LAT...LON   27989708 27089734 26699731 25919734 25849761 
            25969773 25999818 26179850 26769856 27609824