MESOSCALE PRECIPITATION DISCUSSION 0214
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
320 PM EDT TUE MAY 17 2016
 
AREAS AFFECTED...PORTIONS OF THE FL PENINSULA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 171919Z - 180119Z
 
SUMMARY...CONVECTION IS EXPANDING IN COVERAGE AND INTENSITY NEAR A
DEW POINT GRADIENT AND SEA BREEZE BOUNDARIES.  WITH HOURLY RAIN
RATES TO 3" POSSIBLE, FLASH FLOODING IS POSSIBLE, PARTICULARLY
WITHIN URBAN AREAS.

DISCUSSION...A DEW POINT BOUNDARY ACROSS THE CENTRAL PENINSULA
FROM TAMPA TO SOUTH OF MELBOURNE ALONG WITH SEA BREEZE BOUNDARIES
HAVE ACTED TO FOCUS CONVECTION WITH HEAVY RAINFALL.  A CONVECTIVE
MESOSCALE WAVE HAS MARCHED EASTWARD AT 20 KTS SINCE ITS INCEPTION
ALONG THE LOWER TX COAST 36 HOURS AGO, WHICH IS LIKELY AIDING LIFT
ACROSS THE REGION.  INFLOW AT 850 HPA IS CONVERGENT AND SOUTHERLY
AT 20 KTS, ADVECTING IN MLCAPES OF 2500-3500 J/KG. PRECIPITABLE
WATER VALUES ARE 2-2.25" PER GPS VALUES.  

THE GALVEZ/DAVISON INDEX IS SHOWING VALUES OF 40-50, WHICH
INDICATES THE LIKELIHOOD OF NUMEROUS THUNDERSTORMS ACROSS THE
CENTRAL AND SOUTHERN FL PENINSULA.  THE MESOSCALE/CAM GUIDANCE IS
UNANIMOUS IN DEPICTING 3-5" TOTALS, WITH A FEW PIECES OF GUIDANCE
INDICATING 7"+ MAXIMA.  THIS COULD FALL QUICKLY AS THE AVAILABLE
MOISTURE SUPPORTS HOURLY RAIN RATES UP TO 3", WHICH HAS ALREADY
BEEN INDICATED ON RADAR.  CELL MERGERS AND SHORT PERIODS OF
TRAINING SHOULD LEAD TO THE HIGH RAIN RATES.  THE EXPECTATION IS
FOR THE DEW POINT BOUNDARY TO BECOME A MORE EFFECTIVE THERMAL
BOUNDARY DUE TO OUTFLOW BOUNDARIES FROM CONVECTION IN CENTRAL FL. 
ORGANIZED CONVECTION SHOULD TURN EASTWARD, THOUGH THE 12Z GFS
INDICATES A PERIOD OF MINIMAL FORWARD PROPAGATION AROUND 00Z,
WHICH INDICATES THE POSSIBILITY OF BACK BUILDING CONVECTION AS 850
HPA INFLOW INCREASES.  DUE TO AVAILABLE INSTABILITY, THE HEAVY
RAIN THREAT SHOULD BE MOST PERSISTENT ACROSS PORTIONS OF CENTRAL
AND SOUTHERN FL.  THE WILD CARD IS THE GULF CONVECTION WHICH COULD
INVADE THE WEST COAST OF THE CENTRAL AND SOUTHERN PENINSULA
TOWARDS THE END OF THE MPD PERIOD.  

ROTH

ATTN...WFO...JAX...MFL...MLB...TBW...

ATTN...RFC...SERFC...

LAT...LON   30368137 28958057 28138020 26947989 25488010 
            25098104 26028207 27198270 28808283 29958236