SWODY1
SPC AC 181630
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1030 AM CST FRI DEC 18 2009
VALID 181630Z - 191200Z
...THERE IS A SLGT RISK OF SVR TSTMS OVER FLORIDA...
...SYNOPSIS...
SURFACE LOW IS FORECAST TO TRACK INLAND FROM FL PNHDL TO GA/FL
BORDER THROUGH LATE THIS AFTERNOON WITH SECONDARY CYCLOGENESIS
LIKELY ALONG SC COASTAL FRONT BY THIS EVENING. THIS PROCESS OCCURS
AS A SHORT WAVE TROUGH...NOW APPROACHING THE LOWER MS VALLEY...LENDS
DYNAMIC SUPPORT AND PHASES WITH A VIGOROUS SRN STREAM DISTURBANCE
NOW LIFTING NEWD ACROSS NERN GULF OF MEXICO AND FL. RAPIDLY
INTENSIFYING DEEP-LAYER COASTAL CYCLONE WILL MOVE TO THE NC OUTER
BANKS BY SATURDAY MORNING WITH ASSOCIATED COLD FRONT WELL EAST OF FL
BY THAT TIME.
...N FL INTO SRN GA...
DESPITE STRONG FORCING FOR ASCENT WITH THE DEVELOPING TROUGH AND
SURFACE LOW OVER THE NRN GULF THIS MORNING...DEEP CONVECTION NEAR
THE LOW CENTER HAS BEEN ABSENT. DRY SLOT AND WEAK INSTABILITY OVER
THE NRN GULF HAVE LIKELY CONTRIBUTED TO A LACK OF GREATER TSTM
COVERAGE. PRIMARY CONCERN IS DEVELOPMENT OF WEAK SURFACE-BASED
INSTABILITY WITH DIURNAL HEATING NEAR THE SURFACE LOW AND ALONG
STRONG BAROCLINIC ZONE INTO NRN FL/SRN GA THIS AFTERNOON. CURRENT
INDICATIONS SUGGEST THERE REMAINS A LOW PROBABILITY TORNADO
POTENTIAL ACROSS THESE AREAS IF ANY DISCRETE LONGER-LIVED TSTMS CAN
DEVELOP COINCIDENT WITH AN INCREASE IN SURFACE-BASED INSTABILITY.
THE WINDOW IN TIME/SPACE FOR ANY TORNADO WOULD BE LIMITED BY BOTH
COVERAGE OF SURFACE-BASED INSTABILITY AND THE FACT THAT LARGE SCALE
MASS TRANSPORT...AND MORE FAVORABLE SHEAR AND FORCING...WILL QUICKLY
TRANSITION TO THE EAST COAST LATER TODAY.
...NRN TO CNTRL FL...
THERE IS A GREATER CHANCE FOR AT LEAST WEAK SURFACE-BASED
DESTABILIZATION /MLCAPE 250-500 J PER KG/ ACROSS PORTIONS OF
NRN/CNTRL FL THROUGH LATER THIS AFTERNOON. SOME OF THIS AREA HAS
BEEN PRECIPITATION-FREE THIS MORNING...AND CLOUD COVER MAY DIMINISH
OVER THE NEXT FEW HOURS AS DRY SLOT MOVES EAST AHEAD OF SURFACE COLD
FRONT. IF THIS CAN OCCUR...CONVECTION ASSOCIATED WITH LIFT ALONG THE
ADVANCING FRONT MAY POSE SOME WIND/TORNADO THREAT...GIVEN MAGNITUDE
OF DEEP-LAYER WIND FIELDS...AS THE FRONT MOVES ACROSS THIS PART OF
THE PENINSULA BETWEEN 21 AND O3 UTC.
...SOUTH FL...
RADAR AND SATELLITE IMAGERY SUGGEST THE BACK EDGE OF MID-LEVEL
DISTURBANCE IS NOW SHIFTING EWD ACROSS S FL. AT LEAST TWO MCV-TYPE
ROTATIONAL CLUSTERS APPEAR IN RADAR DATA MOVING
STEADILY TOWARD THE EAST COAST. AHEAD OF THIS ORGANIZED
ACTIVITY...NUMEROUS SUPERCELLS WITH SOME TORNADO POTENTIAL CONTINUE
OFF THE SE COAST INLAND TO DADE COUNTY. WITH THE PASSAGE OF THIS
FIRST AREA OF DISTURBED WEATHER...A BREAK IN DEEP CONVECTION IS
LIKELY BEFORE SEVERE POTENTIAL INCREASES AGAIN LATER TODAY WITH
APPROACH OF POSSIBLE PRE-FRONTAL SQUALL LINE.
..CARBIN.. 12/18/2009
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