SWODY2
SPC AC 241730
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1130 AM CST MON DEC 24 2007
VALID 251200Z - 261200Z
..NO SVR TSTM AREAS FORECAST...
..SYNOPSIS...
IN MID/UPPER LEVELS...BROADLY CYCLONIC FLOW ACROSS CONUS WILL
CONTINUE ON LARGE SCALE -- PUNCTUATED BY SEVERAL PROGRESSIVE
SHORTWAVE TROUGHS. PRIMARY PERTURBATION OF CONCERN FOR THIS
FORECAST IS EVIDENT IN MOISTURE CHANNEL IMAGERY ATTM OVER SRN
PLAINS. THIS TROUGH IS FCST TO STRENGTHEN THROUGH EARLY DAY-2 AND
PIVOT EWD LATE IN PERIOD ACROSS DIXIE AS TROUGH NOW OVER PACIFIC NW
DIGS SEWD. STG CONSENSUS EXISTS AMONGST LATEST OPERATIONAL
MODELS...AS WELL AS SREF MEMBERS...THAT THIS FEATURE WILL ASSUME
NEUTRAL TO SLIGHTLY NEGATIVE TILT AS IT CROSSES AL/GA AND SC...AND
ALSO...WILL LOSE AMPLITUDE AND EJECT NEWD OVERNIGHT OVER CAROLINAS.
AT SFC...LOW LEVEL BAROCLINIC ZONE IS ANALYZED IN SFC-925 MB CHARTS
AND IS EVIDENT IN VIS IMAGERY FROM NEAR 30N77W SWWD ACROSS CENTRAL
FL AND SERN GULF. APCH OF UPPER WAVE SHOULD FOMENT SFC CYCLOGENESIS
ALONG THIS FRONT...WHICH SHOULD REMAIN QUASISTATIONARY UNTIL AT
LEAST FIRST 6 HOURS OF PERIOD. CONSIDERABLE UNCERTAINTY EXISTS
REGARDING SPECIFIC LOCATION OF INITIAL CYCLOGENESIS...PARTLY BECAUSE
OF POOR OBSERVATIONAL SAMPLING OF CURRENT FRONTAL CHARACTERISTICS
OVER OCEAN WATERS AND PARTLY BECAUSE OF WIDE DISPARITIES IN
TIMING/PLACEMENT OF LOW FORMATION IN SHORT-RANGE GUIDANCE.
HOWEVER...MOST MODELS REASONABLY CONVERGE ON SOLUTION OF DEEPENING
SFC LOW OFF SC/GA COASTS...AND OVER GULF STREAM...BY 26/06Z-26/09Z
TIME FRAME.
..SERN CONUS...
ZONE OF STRONGEST LARGE SCALE ASCENT/DESTABILIZATION -- IMMEDIATELY
PRECEDING MID/UPPER SHORTWAVE TROUGH -- SHOULD CROSS AL...FL
PANHANDLE AND GA BEFORE 25/12Z-26/00Z TIME FRAME. FCST SOUNDINGS
SUGGEST ACCOMPANYING COOLING ALOFT MAY STEEPEN MIDLEVEL LAPSE RATES
SUFFICIENTLY -- IN ENVIRONMENT OF AT LEAST MRGL MOISTURE ABOVE SFC
-- TO SUPPORT ELEVATED MUCAPES UP TO ABOUT 100 J/KG ACROSS SERN
AL...FL PANHANDLE AND GA DURING DAYLIGHT HOURS. WHILE THUNDER
CANNOT BE RULED OUT TOTALLY WITH SUCH A PRECIP BAND...FCST SOUNDINGS
SUGGEST MOST OR ALL THE BUOYANCY WILL REMAIN UNDERNEATH OPTIMAL
CHARGE SEPARATION LAYERS FOR LIGHTNING. GIVEN THIS PROFILE AND
WEAKNESS OF BUOYANCY...WILL REFRAIN FROM GEN THUNDER OUTLOOK FOR
INITIAL BAND FOR NOW.
SECOND AREA OF CONVECTIVE DEVELOPMENT IS LIKELY OFFSHORE ATLANTIC
COAST OF GA AND CAROLINAS -- AND PERHAPS OFF NERN FL -- LATE IN
PERIOD. LARGE SCALE ASCENT ALOFT...WITH APCH OF MIDLEVEL TROUGH --
WILL BECOME INCREASINGLY JUXTAPOSED WITH STRENGTHENING LOW LEVEL WAA
AND MOIST ADVECTION ASSOCIATED WITH WARM CONVEYOR NE-NW OF DEEPENING
SFC LOW. SFC-BASED CONVECTION SHOULD REMAIN OFFSHORE -- ALONG AND
SE OF FRONTAL ZONE WHERE STRONGEST VERTICAL HEAT FLUXES AND BUOYANCY
ARE EXPECTED. HOWEVER...SOME THUNDER SHOULD DEVELOP INVOF COAST
WHERE ELEVATED MUCAPES UP TO ABOUT 250 J/KG ARE POSSIBLE.
.EDWARDS.. 12/24/2007
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