SWODY2
SPC AC 251726
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1126 AM CST TUE DEC 25 2007
VALID 261200Z - 271200Z
..NO SVR TSTM AREAS FORECAST...
..SYNOPSIS...
PROGRESSIVE MID/UPPER LEVEL SHORTWAVE PATTERN FCST TO CONTINUE
ACROSS CONUS...AMIDST LARGER SCALE CYCLONIC FLOW FIELD. LEADING
SHORTWAVE TROUGH -- NOW EVIDENT IN MOISTURE CHANNEL IMAGERY AND
VWP/PROFILER WINDS OVER N-CENTRAL GULF AND MS -- CONTAINS CLOSED LOW
OVER MS THAT SHOULD MOVE ENEWD OVER CAROLINAS AT 26/12Z...BEFORE
MOVING OFFSHORE TIDEWATER REGION. ACCOMPANYING TROUGH SHOULD
DEAMPLIFY SLIGHTLY...AS UPSTREAM PERTURBATION NOW OVER W-CENTRAL
ROCKIES...SRN GREAT BASIN...AND NWRN MEX...PIVOTS EWD. ABOUT 1/3 OF
LATEST SREF MEMBERSHIP...AS WELL AS OPERATIONAL NAM...INDICATES
DISTINCT 500 MB LOW WILL EVOLVE WITHIN TROUGH ACROSS NM LATE DAY-1
AND OVER W TX DAY-2...WITH 90-100 KT FLOW AROUND ITS SWRN QUADRANT
AT SAME LEVEL. COMPARISON OF RAOB ANALYSES WITH MODEL
INITIALIZATIONS...AS WELL AS CURRENT SATELLITE TRENDS...SUPPORT THIS
SOMEWHAT STRONGER SOLUTION AS OPPOSED TO REMAINDER OF GUIDANCE.
AS A RESULT...FRONTOGENESIS AND CYCLOGENESIS THAT IS FCST TO OCCUR
ACROSS CENTRAL/SRN TX EARLY IN PERIOD MAY BE SOMEWHAT STRONGER THAN
PROGGED IN MOST MODELS. PRIND SFC LOW SHOULD MOVE FROM CENTRAL TX
ENEWD ACROSS SRN AR...TO NRN MS/WRN TN REGION BY 27/00Z...BEFORE
WEAKENING FARTHER NE AS RELATED MIDLEVEL WAVE LIKEWISE DEAMPLIFIES.
BY END OF PERIOD...ACCELERATING/WEAKENING MIDLEVEL TROUGH IS
EXPECTED OVER CENTRAL APPALACHIANS...AS YET ANOTHER UPSTREAM WAVE --
NOW OFFSHORE PACIFIC NW -- DIGS SEWD ACROSS 4-CORNERS REGION.
MEANWHILE...ATLANTIC SFC LOW -- ASSOCIATED WITH LEADING TROUGH --
SHOULD BRUSH OUTER BANKS OR REMAIN BARELY OFFSHORE...IN KEEPING WITH
SPECTRAL/ECMWF GUIDANCE AND CONSENSUS OF SREF RSM/WRF RUNS...AS
OPPOSED TO MORE WRN OPERATIONAL NAM PROG AND WRN-BIASED ETA MEMBERS
OF SREF SUITE. OUR MORE ERN FCST TRACK SHOULD KEEP SFC WARM SECTOR
AND RICHEST MARINE AIR PREDOMINANTLY OVER WATER...MITIGATING SVR
THREAT. HOWEVER...GEN TSTM POTENTIAL SHOULD CARRY OVER FOR A FEW
HOURS FROM DAY-1 ALONG COAST BEFORE DEEP-LAYER PERTURBATION EJECTS
SEAWARD.
..W GULF COASTAL PLAIN TO LOWER MS VALLEY...
FAVORABLE FRONTOGENETIC FORCING AND AT LEAST MRGL LOW LEVEL MOISTURE
MAY JUXTAPOSE SUFFICIENTLY TO SUPPORT ELEVATED TSTMS ACROSS PORTIONS
CENTRAL/SRN TX AS EARLY AS AROUND 26/12Z. BAND OF CONVECTION SHOULD
SHIFT ENEWD-NEWD WHILE BACKBUILDING ON SRN END THROUGH MUCH OF
DAY...YIELDING NET EXPANSION ACROSS AR/LA...MS DELTA REGION AND NWRN
GULF...THROUGH AT LEAST 26/21Z. REGIME INLAND THEN SHOULD WEAKEN
OVERNIGHT AS LOW-MIDLEVEL PERTURBATION ALSO WEAKENS...AND RETURN
FLOW DIMINISHES. RELATIVELY RICH LOW LEVEL THETAE SHOULD MAINTAIN
LINE OF TSTMS ACROSS GULF...POSSIBLY EXTENDING NWD ACROSS SRN LA.
SATELLITE-DERIVED PW IMAGERY AND VIS LOW CLOUD CHARACTERISTICS
SUPPORT SFC OBSERVATIONAL INDICATIONS OF RICH LOW LEVEL MOISTURE
ACROSS S-CENTRAL/SWRN GULF...NEAR AND S OF OLD FRONTAL ZONE. AS
FRONTOLYSIS CONTINUES OVER WRN GULF...PRIND RETURN FLOW SHOULD BE
STRONG ENOUGH THROUGH MIDDLE OF PERIOD TO BRING INCREASINGLY MOIST
TRAJECTORIES ABOVE SFC...INLAND ACROSS SE TX AND LOWER MS VALLEY.
THIS WILL SUPPORT MUCAPES AROUND 500 J/KG NEAR COAST...DIMINISHING
AND BECOMING PROGRESSIVELY MORE ELEVATED WITH NWD EXTENT. FCST
SOUNDINGS SUGGEST EFFECTIVE BULK SHEARS 40-55 KT MAY SUPPORT AT
LEAST MRGL SVR POTENTIAL WITH SOME OF THIS ACTIVITY...PRIMARILY
HAIL. STG GUSTS MAY OCCUR VERY CLOSE TO COAST...HOWEVER...WHERE
NEAR-SFC STABLE LAYER BECOME VERY SHALLOW.
THERE ALSO IS SMALL BUT NON-NEGLIGIBLE POTENTIAL FOR SFC--BASED
EFFECTIVE LIFTED PARCELS ALONG SE TX/SWRN LA COAST...WHICH WOULD
OCCUR IN ENVIRONMENT OF ENLARGED HODOGRAPHS AND STG LOW LEVEL SRH.
THIS COULD YIELD POTENTIAL FOR DAMAGING GUSTS OR A FEW TORNADOES
GIVEN FAVORABLE SUPERCELLULAR/BOWING STORM MODES WITHIN CONVECTIVE
BAND. THREAT APPEARS TOO MRGL/CONDITIONAL TO WARRANT CATEGORICAL
OUTLOOK ATTM...BUT WILL BE MONITORED FOR POSSIBLE UPGRADE.
.EDWARDS.. 12/25/2007
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