MESOSCALE DISCUSSION 0317
   NWS STORM PREDICTION CENTER NORMAN OK
   0951 AM CST FRI MAR 21 2003
   
   AREAS AFFECTED...CNTRL FL PEN
   
   CONCERNING...SEVERE THUNDERSTORM POTENTIAL 
   
   VALID 211551Z - 211745Z
   
   WW IS NOT CURRENTLY ANTICIPATED DUE TO EXPECTED SHORT TERM
   DURATION OF SEVERE THREAT...BUT TRENDS WILL CONTINUE TO BE
   MONITORED.
   
   CONVECTIVE ACTIVITY HAS INTENSIFIED SOME DURING THE PAST HOUR
   ALONG PRE-FRONTAL WIND SHIFT ACROSS THE CENTRAL FLORIDA
   PENINSULA... ROUGHLY ALONG/WEST OF INTERSTATE 4.  THIS APPEARS TO
   BE IN RESPONSE PRIMARILY TO DAYTIME HEATING/BOUNDARY LAYER
   DESTABILIZATION...AND INCREASE IN MID/UPPER FORCING FOR UPWARD
   VERTICAL MOTION ASSOCIATED WITH UPSTREAM SHORT WAVE TROUGH.  THIS
   FEATURE IS EVIDENT IN LATEST WATER VAPOR LOOPS LIFTING ACROSS THE
   WESTERN FLORIDA PANHANDLE AND NORTHEASTERN GULF OF MEXICO...AND
   PROGGED TO RAPIDLY CONTINUE NORTHEASTWARD ACROSS GEORGIA AND THE
   REMAINDER OF NORTHERN FLORIDA BY EARLY AFTERNOON.
   
   SUBSTANTIAL LOW-LEVEL CONVERGENCE IS NOT READILY APPARENT IN
   SURFACE DATA ALONG PRE-FRONTAL BOUNDARY...AND AS BOUNDARY LAYER
   FLOW VEERS TO A MORE WESTERLY COMPONENT ACROSS THE CENTRAL
   PENINSULA WITH PASSAGE OF UPPER SYSTEM...THIS SHOULD WEAKEN
   FURTHER.  THIS MAY LIMIT CONVECTIVE THREAT.  HOWEVER...GIVEN
   PRESENCE OF MODERATE INSTABILITY WITH CAPE ON THE ORDER OF 1000
   TO 2000 J/KG...MODERATELY STRONG VERTICAL SHEAR PROFILES ON
   SOUTHERN FRINGE OF WESTERLIES WILL PROVIDE AT LEAST SOME SEVERE
   THREAT WITH ONGOING ACTIVITY THROUGH 18-20Z TIME FRAME.
   
   ..KERR.. 03/21/2003
   
   
   ATTN...WFO...MLB...TBW...MLB...TBW...
   
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