MESOSCALE DISCUSSION 2256
   NWS STORM PREDICTION CENTER NORMAN OK
   0339 AM CDT MON OCT 17 2011
   
   AREAS AFFECTED...PORTIONS LOWER-MIDDLE FL KEYS.
   
   CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY 
   
   VALID 170839Z - 171115Z
   
   RADAR AND SATELLITE TRENDS SHOW COVERAGE OF RELATIVELY DISCRETE
   CONVECTION INCREASING FROM LOWER KEYS SEWD ACROSS STRAITS AT LEAST
   180 NM PAST CAY SAL BANK AND JUST OFFSHORE N-CENTRAL CUBA. 
   WATERSPOUTS FROM ROTATING SHOWERS ARE POSSIBLE OVER WATERS NEAR
   KEYS...AND A BRIEF TORNADO CANNOT BE RULED OUT OVER LOWER-MIDDLE
   KEYS THROUGH REMAINDER MORNING.
   
   DISCRETE CONVECTIVE ELEMENTS SHOULD REMAIN RELATIVELY SHALLOW AND
   SMALL WITH LITTLE OR NO LIGHTNING PRODUCTION -- I.E. OCNL
   WARM-CLOUD/MINI-SUPERCELLULAR SHOWERS.  EXPECT WEAK MID-UPPER LEVEL
   LAPSE RATES AND RELATIVELY BOTTOM-HEAVY PROFILE OF BUOYANCY.  RICH
   LOW-LEVEL THETAE AND 2.25-2.5 INCH PW SUPPORTS MLCAPE AROUND 500
   J/KG OVER STRAITS...DECREASING NWD ACROSS FL BAY.  LOWER-MIDDLE KEYS
   AND ADJACENT WATERS LIE WITHIN NERN FRINGE OF ENHANCED
   BOUNDARY-LAYER SHEAR...BASED ON EYW/MIA VWP...OBSERVED SFC WINDS AND
   LOW-LEVEL MODEL ANALYSES.  0-1 KM SRH HAS BEEN HOLDING STEADY IN
   250-300 J/KG RANGE FOR SEVERAL HOURS AROUND EYW...BENEATH 20-30 KT
   SELY LLJ THAT LIKELY STRENGTHENS SOMEWHAT FARTHER SW TOWARD AREAS
   OFFSHORE NWRN CUBA.  BULK OF STRONGER AND MORE CONSISTENTLY
   ORGANIZED CONVECTION SHOULD REMAIN S AND W OF LOWER KEYS...WHERE RUC
   AND ETA-KF FCST SOUNDINGS SUGGEST COMPARABLE BUOYANCY AND LARGER
   LOW-LEVEL HODOGRAPHS.  HOWEVER...WIND PROFILES WILL CONTINUE TO
   SUPPORT INTERMITTENT CONVECTIVE-SCALE ROTATION WITH CELLS APCHG
   LOWER-MIDDLE KEYS.
   
   REF NHC TROPICAL WEATHER OUTLOOKS -- WMO HEADER ABNT20 KNHC -- FOR
   LATEST FCST GUIDANCE ON RELATED AREA OF LOW PRESSURE INVOF NERN
   YUCATAN PENINSULA AND ITS POTENTIAL FOR TROPICAL DEVELOPMENT.
   
   ..EDWARDS.. 10/17/2011
   
   
   ATTN...WFO...KEY...
   
   LAT...LON   24908058 24758090 24628122 24628146 24538172 24538181
               24528221 24608220 24578199 24598172 24768145 24758131
               24738114 24868082 24948067 24908058