MESOSCALE PRECIPITATION DISCUSSION 0146
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
323 AM EDT THU JUL 04 2013
 
AREAS AFFECTED...SOUTHERN ALABAMA...FLORIDA PANHANDLE 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 040722Z - 041222Z
 
SUMMARY...SLOW STORM MOTION AND ORGANIZED LIFT IN A TROPICAL
ENVIRONMENT MAY RESULT IN VERY HEAVY RAIN AND FLASH FLOODING.

DISCUSSION...ORGANIZED LIFT WAS INCREASING TOWARD THIS AREA AS
EVIDENCED NOT ONLY BY ONGOING DEEP CONVECTION EAST OF MOBILE AL AT
07Z...BUT ALSO BY A FLARE UP OF CELLS OFF THE LA COAST. RAP
FORECASTS CARRY A MID LEVEL VORTICITY CENTER NORTHWARD ACROSS
AL/FL THROUGH 12Z...SUGGESTING SUSTAINED LIFT WITHIN A VERY MOIST
TROPICAL ENVIRONMENT WITH PW VALUES AROUND 2.25 INCHES.

FURTHERING THE CONCERN FOR EXCESSIVE RAINFALL AMOUNTS IS THE
LIKELIHOOD OF STORM MOTIONS LESS THAN 10 KT AND NEAR ZERO AT
TIMES. SHEAR IN THE CLOUD LAYER IS SUFFICIENT FOR UPDRAFT
ROTATION...WITH BUNKERS RIGHT MOVERS E OR ENE AT 5 KT...WHILE
CORFIDI VECTORS PREDICT ANY SMALL SCALE MCS WOULD BE STATIONARY OR
MOVE EASTERLY AT 5 KT. THE RESULT MAY BE THAT THE ONGOING HEAVY
RAIN IN ESCAMBIA COUNTY FL AT 07Z DRIFTS SLOWLY EAST...PRODUCING
RAIN CAPABLE OF EXCEEDING THE 3-4 INCH FLASH FLOOD GUIDANCE IN
THIS AREA.

THE HIRES WRF-ARW AND NSSL WRF WERE PERFORMING WELL WITH RESPECT
TO TIMING AND PLACEMENT OF THIS EVENT. THEY SUGGEST THE HEAVY RAIN
THREAT SHOULD BE PRIMARILY LIMITED TO WITHIN 1 OR 2 COUNTIES OF
THE COAST...AS THE POOL OF AVAILABLE INSTABILITY IS OFFSHORE AND
BEING ADVECTED IN JUST ABOVE THE SURFACE. THE ENVIRONMENT OVER
SOUTHEAST AL AND FARTHER EAST INTO THE FL PANHANDLE MAY BECOME
MORE FAVORABLE WITH TIME...HOWEVER...AS THE LOW LEVEL JET VEERS
SHIFT THETA-E FLUX TOWARD THE NORTH AND EAST. THE FLUX OF 850 MB
MOISTURE IS FORECAST BY THE GFS TO PEAK AT 4-5 STANDARD DEVIATIONS
ABOVE CLIMATOLOGY BY 12Z OVER THE FLORIDA PANHANDLE...INCLUDING
OVER AREAS THAT RECEIVED INTENSE RAINFALL ON WEDNESDAY.

BURKE

ATTN...WFO...TAE...MOB...

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

LAT...LON   29628419 30648477 31378539 31638649 31368804 30078818
            29318688 29128496 29628419