MESOSCALE PRECIPITATION DISCUSSION 0663
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1020 AM EDT TUE SEP 13 2016
 
AREAS AFFECTED......NORTHEAST FLORIDA TO SOUTHEAST GEORGIA... 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 131420Z - 132020Z
 
SUMMARY...BANDS OF HEAVY SHOWERS/STORMS OVER THE COASTAL WATERS
EXPECTED TO MOVE ONSHORE INTO NORTHEAST FLORIDA AND ADJACENT
SOUTHEAST GEORGIA WITH ISOLATED FLASH FLOODING POSSIBLE WHERE
BANDS TRAIN...

DISCUSSION...RADAR AND SURFACE OBSERVATIONS INDICATE A CYCLONIC
CIRCULATION HAS FORMED OVER EAST CENTRAL FLORIDA. BANDS OF SHOWERS
HAVE DEVELOPED NEAR THE CENTER OF CIRCULATION AND EAST OF THE
CIRCULATION OVER THE ADJACENT COASTAL WATERS. 

THE MODELS/HIGH RESOLUTION ENSEMBLES SHOW A SLOW NORTHWEST
MOVEMENT OF THE CIRCULATION ACROSS NORTHERN FLORIDA THIS
AFTERNOON. 
BANDS OF STRONG LOW-MID LEVEL MOISTURE CONVERGENCE AND MOISTURE
FLUX (SHOWN IN THE GRAPHIC) IN THE REGION SUPPORT STRONG ASCENT
AND PERSISTENCE OF THE BANDS OF RAIN. 

THE 09Z MORNING SOUNDING FROM XMR/KENNEDY SPACE CENTER INDICTED
LAYER MEAN RELATIVE HUMIDITY OF 90 PERCENT PLUS 2.4 INCHES OF
PRECIPITABLE WATER(PW)...WELL ABOVE NORMAL VALUES.  THE RAP
FORECASTS FOR THIS AFTERNOON SHOW AREAS OF 2.5 INCHES OF
PW...COMBINING WITH THE FORECAST ASCENT TO PRODUCE LOCALLY HEAVY
RAIN. 

THE OBSERVED SOUNDING AND SHORT TERM FORECASTS INDICATE SOUTHEAST
FLOW FROM THE SURFACE TO 700 MB WITH LITTLE DIRECTIONAL SHEAR.
THIS SHOULD FAVOR TRAINING IN THE BANDS OF SHOWERS/STORMS THAT
FORM OVER THE REGION...LEADING TO POTENTIAL FOR LOCALLY HEAVY RAIN
AND RESULTANT RUNOFF PROBLEMS...PARTICULARLY FOR ROADS IN THE
AREA...INCLUDING INTERSTATE 95. FLASH FLOOD GUIDANCE VALUES ARE
HIGH AT 4-5 INCHES IN 6 HOURS...SO ONLY ISOLATED LOCATIONS ARE
EXPECTED TO EXCEED THE FLASH FLOOD  GUIDANCE.

THE 09-13Z RUNS OF THE HIGH RESOLUTION RAPID REFRESH
(HRRR)/EXPERIMENTAL HRRR AS WELL AS THE WRF ARW AND NSSL WRF ALL
INDICATE 3-4 INCHES OF RAIN WITH LOCALLY HIGHER MAXIMA IN THE
BANDS OF RAINFALL.  

PETERSEN

ATTN...WFO...JAX...MLB...

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

LAT...LON   30928128 30418086 29408038 28688034 28118060 
            28378103 29128165 30058191 30828192