MESOSCALE DISCUSSION 0757
   NWS STORM PREDICTION CENTER NORMAN OK
   1259 PM CDT THU MAY 12 2011
   
   AREAS AFFECTED...SOUTH FL
   
   CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY 
   
   VALID 121759Z - 122000Z
   
   ISOLATED SVR STORMS WITH LARGE HAIL AND DMGG WINDS WILL BE POSSIBLE
   OVER SOUTH FLORIDA THIS AFTERNOON.
   
   THE AIR MASS OVER SOUTH FLORIDA CONTINUES TO DESTABILIZE THIS
   AFTERNOON...WITH THE 12Z MIAMI SOUNDING ASSIMILATED WITH 17Z SFC
   OBSERVATIONS YIELDING MLCAPE VALUES ON THE ORDER OF 2500-3000 J/KG.
   THIS HAS OCCURRED AS SFC TEMPERATURES WARMED INTO THE UPPER 80S TO
   LOWER 90S...WITH DEWPOINTS FROM THE MIDDLE 60S TO LOWER
   70S...BENEATH A MODESTLY STEEP MID-LEVEL LAPSE RATE ENVIRONMENT --
   I.E. 700-500-MB LAPSE RATE OF 6.6 C PER KM BASED ON 12Z MIAMI
   SOUNDING.
   
   MEANWHILE...VISIBLE SATELLITE IMAGERY REVEALS SEVERAL BOUNDARIES
   THAT WILL LIKELY PLAY A ROLE IN INITIATING/ENHANCING CONVECTION THIS
   AFTERNOON. FIRSTLY...AN ELONGATED NW-SE-ORIENTED CONVERGENCE BAND
   EMANATING FROM A LARGE CYCLONIC GYRE CENTERED OVER THE WRN ATLC
   CURRENTLY EXTENDS OVER THE SERN PENINSULA...AND IS SHIFTING SWWD.
   INTERSECTING THIS BAND ARE N-S-ORIENTED CONVERGENCE-ENHANCED CUMULUS
   LINES OVER THE SRN PENINSULA. DEEP CONVECTION HAS ALREADY STARTED
   INITIATING AT THE INTERSECTION POINTS OVER PORTIONS OF MIAMI-DADE
   COUNTY. MEANWHILE...A LAKE BREEZE OFF LAKE OKEECHOBEE IS MOVING
   SWD...AND WILL ALSO LIKELY ENHANCE CONVECTION.
   
   WITH CONTINUED DIABATIC HEATING...THE PRESENCE OF THE AFOREMENTIONED
   BOUNDARIES...AND THE POTENTIAL DEVELOPMENT OF A SEA BREEZE OFF THE
   WRN FLORIDA COAST...SCATTERED THUNDERSTORMS WILL LIKELY ERUPT DURING
   THE NEXT COUPLE OF HOURS OVER SOUTH FLORIDA. THE DEGREE OF UPWARD
   POTENTIAL BUOYANCY WILL LIKELY RESULT IN VIGOROUS UPDRAFTS. SOME
   MULTICELLULAR ORGANIZATION IS ANTICIPATED...GIVEN EFFECTIVE BULK
   SHEAR MAGNITUDES OF 25 TO 30 KT. THIS IS IN ASSOCIATION WITH
   ENHANCED NNWLY FLOW OVER THE ERN PERIPHERY OF THE SERN CONUS RIDGE.
   ISOLATED INSTANCES OF LARGE HAIL AND DMGG WINDS WILL BE POSSIBLE.
   DUE TO THE LIMITED AREAL EXTENT OF ANY SVR THREAT...A WW IS
   UNLIKELY.
   
   ..COHEN.. 05/12/2011
   
   
   ATTN...WFO...MFL...MLB...KEY...TBW...
   
   LAT...LON   24668057 25068124 25918178 26948212 27188180 27468130
               27438068 26928024 25158003 24668057