MESO: Mesoscale Discussion 1904

ACUS11 KWNS 291101
SWOMCD
SPC MCD 291100
FLZ000-291330-

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

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...MFL...KEY...

LAT...LON 24958062 25148042 25238036 25258038 25208051 25238064
25458055 25958045 26638021 26878010 26848002 26508004
25928011 25658015 25738021 25558030 25388032 25318030
25498018 25468015 25168035 24958062

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