SWODY1
SPC AC 110559
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1159 PM CST WED DEC 10 2008
VALID 111200Z - 121200Z
...THERE IS A SLGT RISK OF SVR TSTMS TIDEWATER TO WRN/NRN FL...
...SYNOPSIS...
LARGE-SCALE UPPER TROUGH FCST TO REMAIN OVER E-CENTRAL NORTH AMERICA
THROUGH PERIOD...FROM HUDSON BAY REGION SSWWD ACROSS WRN/CENTRAL
GULF. SHORTWAVE MID-UPPER LEVEL CYCLONE -- INITIALLY ANALYZED OVER
SE TX VICINITY GLS BAY -- IS ACCOMPANIED BY AT LEAST 100 M PER 12
HOUR 500 MB HEIGHT FALLS AS ANALYZED OVER LOWER TX COAST...WITH
GREATER FALLS LIKELY OVER WRN GULF RAOB DATA VOID. THIS LOW IS
EXPECTED TO PIVOT EWD THROUGH BEGINNING OF THIS DAY-1 PERIOD...THEN
LIFT NEWD ACROSS SRN AL AND OUT OF MEAN TROUGH POSITION. AS THIS
OCCURS...EXPECT PERTURBATION TO DEAMPLIFY AND BECOME OPEN-WAVE IN
CHARACTER AFTER ABOUT 12/00Z. RESULTING TROUGH THEN WILL WEAKEN
CONSIDERABLY AND ACCELERATE ACROSS CAROLINAS DURING 12/06Z-12/12Z
TIME FRAME.
ASSOCIATED SFC CYCLONE -- NOW ANALYZED OVER GULF SW PNS -- IS
EXPECTED TO MOVE INLAND BEFORE 11/12Z...THEN NEWD ALONG INITIALLY
QUASISTATIONARY FRONTAL ZONE ACROSS ERN AL AND NWRN GA EARLY IN
PERIOD...OCCLUDING INVOF NRN GA. OCCLUSION/TRIPLE-POINT LOW THEN
SHOULD LIFT NEWD FROM UPSTATE SC TO SERN VA...WHILE TRAILING COLD
FRONT SWEEPS EWD FROM ERN GULF ACROSS FL PENINSULA. NRN SEGMENT OF
FRONT SHOULD MOVE OFFSHORE NC BY AROUND 12/06Z.
...EARLY PERIOD...FL AND CENTRAL/SRN GA...
EARLY IN PERIOD...SCATTERED-NUMEROUS TSTMS ARE POSSIBLE AHEAD OF
COLD FRONT OVER SC/GA...THEN ALONG OR JUST AHEAD OF FRONT OVER NERN
GULF...MOVING ASHORE FL W COAST. AS SFC LOW MOVES INLAND EARLY IN
PERIOD...ASSOCIATED ISALLOBARIC FORCING AND NEAR-SFC BACKING WILL
CONTRIBUTE TO FAVORABLE VERTICAL SHEAR PROFILES ACROSS PORTIONS FL
PANHANDLE....NRN/WRN FL PENINSULA AND SRN GA.
INITIAL DEVELOPMENT OF GULF LINE HAS OCCURRED ALREADY -- AS EVIDENT
IN IR IMAGERY. FLOW ALONG FL W COAST THEN SHOULD VEER SLIGHTLY WITH
TIME PRIOR TO FROPA...WHICH WILL REDUCE LOW LEVEL SHEAR SLIGHTLY BUT
WHICH ALSO SHOULD INCREASE MOISTURE AND BUOYANCY BY MEANS OF ONSHORE
ADVECTION OF GULF MARINE LAYER. THIS SHOULD ALLOW CONVECTION TO
SURVIVE INLAND....PERHAPS LONG ENOUGH TO BE ENHANCED BY
PRECURSORY/GRADUAL DIURNAL HEATING DURING MID-LATE MORNING HOURS.
SVR POTENTIAL BECOMES WEAKER AND MORE CONDITIONAL WITH SWD EXTENT
OVER FL PENINSULA BECAUSE OF CONTINUING VEERING...AND RESULTING
WEAKENING TRENDS OF SHEAR/CONVERGENCE WITH TIME. THEREFORE...SVR
PROBABILITIES ARE KEPT AT MRGL LEVELS ATTM FOR SRN PENINSULA. MRGL
BUOYANCY AND PERHAPS MESSY...CLUSTERED OR LINEAR CONVECTIVE MODES
WILL TEMPER BUT NOT REMOVE SVR THREAT...WHICH CONSISTS MAINLY OF
DAMAGING GUSTS AND A FEW TORNADOES POSSIBLE WITH BOW/LEWP FORMATIONS
AND PERHAPS EMBEDDED SUPERCELLS.
...TIDEWATER TO SRN ATLANTIC COAST REGION...
STRENGTHENING SHEAR AND AT LEAST MRGLLY FAVORABLE BUOYANCY WILL
SUPPORT SVR THREAT FROM ERN GA NEWD TO TIDEWATER AREA DURING
AFTERNOON...PRIOR TO PASSAGE OF FRONT OR PREFRONTAL
CONVECTIVE/CONVERGENCE BELT. ATTM IT APPEARS THAT
ONGOING/PRECURSORY PRECIP...CLOUD COVER...RESULTING SUPPRESSION OF
DIABATIC SFC HEATING...AND LACK OF STEEPER MIDLEVEL LAPSE RATES WILL
RESTRICT DESTABILIZATION ACROSS THIS REGION...KEEPING MLCAPES BELOW
ABOUT 750 J/KG MOST AREAS. HOWEVER...EVIDENCE OF GREATER
DESTABILIZATION MAY COMPEL UPGRADE IN SUCCEEDING OUTLOOKS...GIVEN
STRENGTH OF KINEMATIC FIELDS EXPECTED.
MOST SUITABLE JUXTAPOSITION OF SUSTAINED/FAVORABLE SFC
THETAE...DEEP-LAYER SHEAR AND FOCI FOR RELATIVELY DENSE CONVECTIVE
COVERAGE SHOULD BE ACROSS MUCH OF CENTRAL/SRN CAROLINAS DURING
AFTERNOON...HENCE MAXIMIZED WIND PROBABILITIES IN THAT REGION.
50-60 KT LLJ IS FCST JUST ABOVE SFC...AND STG MOMENTUM ALOFT MAY BE
BROUGHT TO SFC IN DOWNDRAFTS TO YIELD WIND DAMAGE. FCST SOUNDINGS
INDICATE 50-60 KT EFFECTIVE SHEAR MAGNITUDES ARE POSSIBLE...WITH 0-1
KM SRH 200-300 J/KG...SUPPORTING BOTH BOWING AND SUPERCELLULAR
STRUCTURES CONCURRENT WITH SFC-BASED EFFECTIVE LIFTED PARCELS.
THEREFORE THREAT FOR A FEW TORNADOES ALSO EXISTS.
..EDWARDS.. 12/11/2008
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