Sunday, August 30, 2009

MESO: Mesoscale Discussion 1983

ACUS11 KWNS 301752
SWOMCD
SPC MCD 301752
SCZ000-GAZ000-FLZ000-ALZ000-MSZ000-301945-

MESOSCALE DISCUSSION 1983
NWS STORM PREDICTION CENTER NORMAN OK
1252 PM CDT SUN AUG 30 2009

AREAS AFFECTED...PORTIONS CENTRAL/SRN AL...GA...SC...FL
PANHANDLE...EXTREME SERN MS.

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 301752Z - 301945Z

TSTMS ARE FCST TO INCREASE IN COVERAGE AND INTENSITY THROUGH AT
LEAST MID-AFTERNOON ACROSS DISCUSSION AREA...WITH MAIN CONCERNS
BEING STG-SVR GUSTS AND HEAVY RAINFALL OF 2-3 INCHES/HOUR WITH MOST
INTENSE CELLS.

PRIMARY CONCENTRATIONS OF CONVECTION ARE FCST TO REMAIN IN BANDS OF
ENHANCED DEEP-LAYER ASCENT...AHEAD OF SHORTWAVE TROUGH THAT NOW IS
EVIDENT OVER PORTIONS MS. TROUGH IS FCST TO LIFT ENEWD THROUGH
REMAINDER AFTERNOON...WHILE BANDS OF LIFT -- INITIALLY OVER SERN MS
AND S-CENTRAL AL -- LIKEWISE MOVE ENEWD ACROSS PORTIONS AL/GA.
ADDITIONAL TSTMS ARE DEVELOPING WITHIN BROAD/DIFFUSE BAROCLINIC ZONE
RELATED TO DIFFERENTIAL HEATING FROM SERN AL NEWD ACROSS
W-CENTRAL-NERN GA. COVERAGE WILL REMAIN MORE ISOLATED TO WIDELY
SCATTERED EWD AND SWD TOWARD ATLANTIC/GULF SEA BREEZES AND AHEAD OF
UVV BANDS INITIALLY OVER MS/AL. PRECONVECTIVE AIR MASS CONTINUES TO
DESTABILIZE FAVORABLY...WITH STG SFC HEATING AND MOISTURE RICH
BOUNDARY LAYER -- E.G. DEW POINTS LOW-MID 70S F -- CONTRIBUTING TO
MLCAPE 2000-3000 J/KG BY 20Z. LOW LEVEL FLOW WILL REMAIN
WEAK...LIMITING HODOGRAPH SIZE AND SRH. HOWEVER...ENHANCED
MID-UPPER LEVEL GRADIENT FLOW AHEAD OF TROUGH ALOFT WILL CONTRIBUTE
TO EFFECTIVE SHEAR 35-40 KT OVER BROAD SWATH FROM COASTAL MS/AL TO
CAROLINAS...IN SUPPORT OF ORGANIZATION WITHIN PREDOMINANT
MULTICELLULAR STORM MODE. MRGL SUPERCELL STRUCTURES ALSO ARE
POSSIBLE...BUT GIVEN WEAKNESS OF AMBIENT SHEAR...SUCH MORPHOLOGY
LIKELY WILL REQUIRE LOCALIZED...LOW-LEVEL VORTICITY SUPPLEMENTATION
BY FAVORABLY ORIENTED SEA BREEZE OR OUTFLOW BOUNDARIES WITH WHICH
STORMS CAN INTERACT MORE THAN BRIEFLY.

..EDWARDS.. 08/30/2009

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...CHS...CAE...GSP...JAX...FFC...TAE...BMX...MOB...
LIX...

LAT...LON 32728034 30928284 30448382 30118464 30108504 30598608
30388780 30508936 32278778 32328686 33098506 34508260
34298017 32728034

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