SWODY1
SPC AC 170053
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0653 PM CST SAT JAN 16 2010
VALID 170100Z - 171200Z
...THERE IS A SLGT RISK OF SVR TSTMS SOME OF COASTAL W-CENTRAL/SWRN
FL...
...SYNOPSIS...
SPLIT-FLOW PATTERN ALOFT PREVAILS ACROSS MUCH OF CENTRAL/ERN CONUS.
MID-UPPER LEVEL LOW -- INITIALLY ANALYZED OVER NWRN/N-CENTRAL TX
NEAR RED RIVER -- IS FCST TO MOVE ESEWD ACROSS NRN LA
OVERNIGHT...OPENING INTO SMALL BUT INTENSE SHORTWAVE TROUGH NEAR END
OF PERIOD OVER SWRN MS. MEANWHILE...SEPARATE SHORTWAVE TROUGH --
NOW EVIDENT IN MOISTURE CHANNEL IMAGERY INVOF COASTAL SERN LA -- IS
EXPECTED TO EJECT NEWD ACROSS MIDDLE-ERN TN OVERNIGHT.
AT SFC...LOW ANALYZED NEAR MCB AT 23Z IS FCST TO MOVE NEWD ACROSS AL
OVERNIGHT AND OCCLUDE...AS TRAILING COLD FRONT MOVES EWD ACROSS AL
COAST AND WRN FL PANHANDLE. ADJACENT WARM FRONT HAS BECOME
ILL-DEFINED BECAUSE OF PRIOR CONVECTIVE ACTIVITY...BUT BECOMES
SHARPER AGAIN FROM NEAR OCF TO ABOUT 50 SE SAV...ENEWD TO JUST S OF
BUOY 41004 AND OFFSHORE NC. SECONDARY LOW IS FCST TO FORM DURING
09Z-12Z TIME FRAME AND MOVE NEWD ACROSS ERN SC/SERN NC. DURING LATE
OVERNIGHT HOURS -- GENERALLY AFTER ABOUT 08Z...WARM FRONT MAY
IMPINGE ON NARROW COASTAL AREA BETWEEN SAV-MHX.
...FL...
AMBIENT VERTICAL SHEAR PROFILES WILL REMAIN FAVORABLE ACROSS MOST OF
FL W COAST...ALTHOUGH SOME VEERING OF FLOW TONIGHT WILL REDUCE BOTH
LOW LEVEL CONVERGENCE AND HODOGRAPH SIZE. INITIAL LINE OF TSTMS
FROM OFFSHORE TBW AREA SWWD TO YUCATAN PENINSULA HAS SHOWN STG-SVR
CHARACTERISTICS OVER RELATIVELY WARM WATERS OF ERN GULF...AS EVIDENT
FROM SATELLITE SIGNATURES AND LONG-RANGE RADAR REFLECTIVITY
PATTERNS. HOWEVER..CONVECTION CONSISTENTLY HAS WEAKENED WHEN APCHG
COAST...BECAUSE OF RELATIVELY STABLE/LOW-THETAE BOUNDARY LAYER
PRESENT ACROSS MOST OF CENTRAL FL AND ADJACENT COASTAL WATERS. A FEW
BOW ECHOES OR SUPERCELLS MAY SURVIVE TO COAST...THEREFORE WILL
MAINTAIN NARROW AREA OF CATEGORICAL-CRITERIA PROBABILITIES.
AIR MASS OVER CENTRAL/NRN FL -- CHARACTERIZED BY SFC DEW POINTS
LOW-MID 60S F...WILL UNDERGO ENOUGH DIABATIC COOLING TO MAINTAIN
VERY STG MLCINH INLAND...ALTHOUGH TBW SOUNDING SHOWED 300-400 J/KG
OF WEAKLY CAPPED MLCAPE. MOIST ADVECTION FROM HIGHER-THETAE AIR
MASS OVER S FL AND STRAITS WILL YIELD BUOYANCY ALONG SW COAST MORE
CLOSELY RESEMBLING EYW SOUNDING WITH BETWEEN 500-700 J/KG MLCAPE.
THIS MAY SUPPORT SOME MAINTENANCE OF OFFSHORE CONVECTION A SHORT
DISTANCE INLAND BEFORE WEAKENING.
FARTHER NW ACROSS FL PANHANDLE AND COASTAL BEND...AIR MASS BEHIND
THIS LINE HAS BEEN STABILIZED BY PRIOR CONVECTION/PRECIP...AND AREA
OF RELATIVELY COLD SST CONTRIBUTES TO SHALLOW STABLE LAYER OVER AND
DOWNSTREAM FROM APALACHEE BAY. STILL...SCATTERED TO WIDELY
SCATTERED...MOSTLY ELEVATED TSTMS ARE EXPECTED TO DEVELOP PRIOR TO
COLD FROPA AND MOVE NEWD FROM GULF.
...COASTAL GA/CAROLINAS...
VERY CONDITIONAL POTENTIAL EXISTS FOR SEVERE. ALTHOUGH MORE
PROBABLE OFFSHORE...SFC-BASED SUPERCELL WITH TORNADO...OR DAMAGING
WIND FROM SMALL BOW ECHOES...CANNOT BE RULED OUT TOTALLY NEAR COAST
LATE TONIGHT. HOWEVER...UNCONDITIONAL POTENTIAL STILL APPEARS TOO
LOW TO UPGRADE TO CATEGORICAL SVR OUTLOOK...MAINLY BECAUSE IT
APPEARS THAT BUOYANCY WILL BE VERY WEAK TO NONEXISTENT FOR SFC-BASED
PARCELS.
AMBIENT VERTICAL SHEAR PROFILES WILL BE QUITE FAVORABLE...WITH 50-65
KT OF 0-6 KM SHEAR MAGNITUDE WIDESPREAD ACROSS THIS REGION.
ENLARGED HODOGRAPHS WILL EXIST INVOF SFC WARM FRONT...CONTRIBUTING
TO LIKELIHOOD OF 0-1 KM SRH EXCEEDING 300 J/KG FOR MOST PROBABLE
CELL MOTIONS. MAIN CONCERN IS LACK OF BUOYANCY AND RELATED STG
MLCINH EXPECTED. ATLANTIC AIR MASS S OF WARM FRONT STILL IS
UNDERGOING MODIFICATION...WITH SFC DEW POINTS GENERALLY MID 60S OVER
AND E OF THAT SEGMENT OF GULF STREAM OFF NRN FL...TRENDING TO LOW
60S INVOF WARM FRONT. THIS IS A FEW DEG F LESS THE EARLIER PROGS
FROM OPERATIONAL NAM-WRF...WHICH WAS MOST AGGRESSIVE IN THIS REGARD.
MOIST ADVECTION AND SEVERAL MORE HOURS OF MARINE MODIFICATION
SHOULD BOOST DEW POINTS TO MID 60S CLOSER TO WARM FRONT...BUT THIS
STILL MAY NOT YIELD SUFFICIENT THETAE TO RENDER SFC-BASED EFFECTIVE
INFLOW PARCELS. IMPORTANT LIMITING FACTOR MAY BE VERY WEAK LAPSE
RATES ALOFT...WHICH ARE NOT EXPECTED TO INCREASE APPRECIABLY FROM
THOSE IN 00Z CHS RAOB. ALSO...EXTENSIVE...LONG-LASTING...ANTECEDENT
AREA OF PRECIP WILL MITIGATE INLAND DESTABILIZATION TENDENCIES.
..EDWARDS.. 01/17/2010
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