MESOSCALE DISCUSSION 2153
   NWS STORM PREDICTION CENTER NORMAN OK
   0612 AM CDT THU AUG 14 2003
   
   AREAS AFFECTED...PORTIONS CENTRAL/SRN FL
   
   CONCERNING...SEVERE THUNDERSTORM POTENTIAL...HEAVY RAINFALL 
   
   VALID 141112Z - 141415Z
   
   SCATTERED-NUMEROUS TSTMS IN BROKEN BANDS AND CLUSTERS SHOULD CROSS
   MUCH OF S FL THROUGH AT LEAST 14Z.  RAIN RATES 1.5-2.5 INCHES/HOUR
   POSSIBLE WITH LOCALLY 3-4 INCHES/HOUR. GREATEST SUSTAINED THREAT
   WILL BE OVER MAINLAND FROM INDIAN RIVER/MARTIN/ST LUCIE/PALM
   BEACH/BROWARD COUNTIES...SHIFTING WWD ACROSS LAKE OKEECHOBEE REGION
   TOWARD SRQ/FMY BY LATE MORNING.  ALSO...STRENGTHENING VERTICAL SHEAR
   EXPECTED TO SHIFT WWD FROM ATLANTIC...RESULTING IN INCREASING BUT
   STILL LOW TORNADO PROBABILITIES.  SEVERE THREAT APPEARS
   MARGINAL/ISOLATED ENOUGH ATTM THAT WW IS NOT REQUIRED.
   
   STRONGEST LOW LEVEL CONVERGENCE SHOULD REMAIN INVOF CONVECTIVE BAND
   -- EVIDENT AT 11Z FROM JUST W OF ANDROS ISLAND NNWWD TO NEAR COASTAL
   MARTIN COUNTY. IN ADDITION TO AMBIENT WARM-CLOUD PRECIP PRODUCTION
   PROCESSES...MUCAPE ESTIMATED IN 1000-2000 J/KG RANGE SHOULD SUPPORT
   CONTINUED ENHANCEMENT TO PRECIP PRODUCTION BY DEEP CONVECTIVE
   PROCESSING OF PW ABOVE 2 INCHES AND 17-18 G/KG MEAN MIXING RATIOS.
   
   ALTHOUGH AVAILABLE VWP DATA AND RUC/ETA FCST SOUNDINGS SUGGEST WEAK
   TO NEGATIVE 0-3 KM AGL SHEAR ANOTHER 1-2 HOURS...STRONGER GRADIENT
   FLOW E OF TROUGH SHOULD MOVE OVER AREA AFTER 12Z -- PARTICULARLY
   FROM FLL AREA NWD.  OVER THAT CORRIDOR...0-1 KM SRH 100-150 J/KG AND
   0-3 KM SRH 150-200 J/KG ARE POSSIBLE WITH RIGHTWARD-DEVIANT CELL
   MOTIONS TOWARD NNW OR N.
   
   REF NHC OUTLOOK UNDER WMO HEADER ABNT20 KNHC FOR FCST GUIDANCE
   REGARDING PARENT TROPICAL WAVE.
   
   ..EDWARDS.. 08/14/2003
   
   
   ATTN...WFO...MFL...MLB...EYW...TBW...
   
   27058248 27688042 26788001 25508019 24748087 24458187
   24558214 24718155 25068074 25188118 25568124 25828144
   25878171 26348187 26478220