Tornado Threat for SE FL
Posted by JAC on 9/29/2010, 7:38 am
 MESOSCALE DISCUSSION 1904 NWS STORM PREDICTION CENTER NORMAN OK 0600 AM CDT WED SEP 29 2010 AREAS AFFECTED...PORTIONS SE FL. CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE VALID 291100Z - 291330Z TORNADO POTENTIAL...THOUGH BRIEF/MRGL AT FIRST...MAY BEGIN TO AFFECT NEAR-COAST AREAS FROM UPPER KEYS TO PALM BEACH COUNTY DURING NEXT FEW HOURS...SLOWLY SHIFTING INLAND TO INCLUDE METRO CORRIDOR FROM HST-PBI. MIA VWP HODOGRAPHS HAVE BEEN SMALL...BUT STEADILY INCREASING IN SIZE AND IN CURVATURE DURING PAST COUPLE OF HOURS AS CENTER OF TD 16 BEGAN CROSSING FL STRAITS BETWEEN CUBA AND KEYS. WEAKER HODOGRAPHS HAVE BEEN EVIDENT IN OBSERVED VWP AND MODEL FCST SOUNDINGS WITH WWD EXTENT THROUGH KEYS...CONCURRENT WITH MORE NEBULOUS/WEAKER CONVECTIVE STRUCTURES. THIS TENDENCY SHOULD CONTINUE...REDUCING TORNADO THREAT FROM N THROUGH NW OF CENTER. FURTHER STRENGTHENING OF BOUNDARY-LAYER SHEAR IS EXPECTED NE OF CENTER ALONG SERN FL COAST AND UPPER KEYS AS LOW-LEVEL FLOW INTENSIFIES SLIGHTLY OVER ERN SEMICIRCLE OF SYSTEM...ESPECIALLY IF IT BUILDS TO TS STRENGTH PER NHC FCSTS. OVERNIGHT RADAR DATA HAVE SHOWN OCNL TSTM-SCALE CIRCULATIONS OFFSHORE WITH MOST PERSISTENT/DEEPEST ECHOES...ALSO INDICATING THAT GREATER SRH IS IN PLACE OFFSHORE. SO IS GREATEST BUOYANCY...MLCAPE ESTIMATED 1000-1500 J/KG OVER WATER...OWING TO RELATIVELY MAXIMIZED THETAE THAT IS RELATED TO MARINE HEAT FLUXES OFF GULF STREAM. STRENGTHENING SELY SFC WINDS WOULD ADVECT MORE OF THIS AIR MASS AT LEAST A FEW MILES INLAND...PERHAPS ACROSS MUCH OF MIAMI-DADE/BROWARD/PALM BEACH COUNTIES WITH TIME. MEANWHILE 0-1 KM SRH 150-200 J/KG SHOULD OVERSPREAD GREATER MERIDIONAL EXTENT OF COASTLINE AS FLOW JUST OFF SFC INTENSIFIES. ..EDWARDS.. 09/29/2010  |
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