MESO: Mesoscale Discussion 1743

ACUS11 KWNS 211800
SWOMCD
SPC MCD 211759
SCZ000-GAZ000-FLZ000-212030-

MESOSCALE DISCUSSION 1743
NWS STORM PREDICTION CENTER NORMAN OK
1259 PM CDT WED AUG 21 2013

AREAS AFFECTED...PORTIONS OF ERN/SRN SC...ERN/SRN GA...INTERIOR
SECTIONS OF THE WRN/CNTRL FL PENINSULA...ERN FL PANHANDLE

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY

VALID 211759Z - 212030Z

PROBABILITY OF WATCH ISSUANCE...5 PERCENT

SUMMARY...THE POTENTIAL FOR AN ISOLATED DMGG WIND GUST CANNOT BE
RULED OUT THIS AFTERNOON.

DISCUSSION...VISIBLE SATELLITE DATA INDICATE DEEPENING
BOUNDARY-LAYER CUMULUS WITHIN A DESTABILIZING...MOIST AIR MASS
CHARACTERIZED BY PW VALUES AROUND 1.75-2.00 INCHES PER GPS DATA.
DIURNAL HEATING AMIDST LOWER/MIDDLE 70S SFC DEWPOINTS HAS
CONTRIBUTED TO MODERATE TO LOCALLY STRONG INSTABILITY IN AREAS VOID
OF PRIOR CONVECTIVE OVERTURNING...AND THIS WILL SUPPORT A CONTINUED
UPTICK IN THE NUMBER/INTENSITY OF THUNDERSTORMS DURING THE NEXT FEW
HOURS WITH LITTLE CAPPING IN PLACE.

LOW-LEVEL ASCENT FOCUSING GREATER THUNDERSTORM COVERAGE WILL LIKELY
BE FOCUSED INVOF A DEVELOPING W-FLORIDA-COAST SEA BREEZE FRONT ALONG
WHICH CONVERGENCE WILL BE BOLSTERED BY IMPINGING DEEP ELY FLOW
SAMPLED BY TBW VWP DATA. STORMS WILL LIKELY BECOME NUMEROUS OVER THE
WRN FL PENINSULA DURING THE NEXT FEW HOURS...WITH WWD-MOVING COLD
POOLS EVENTUALLY SHUNTING THE GREATER CONVECTIVE POTENTIAL OFFSHORE
BY THIS EVENING. ASCENT WILL ALSO BE AUGMENTED ALONG AN OUTFLOW
BOUNDARY THAT PRECEDES A DISORGANIZED AND CONVECTIVELY-ENHANCED COLD
POOL ADVANCING INLAND OVER NRN FL AND SRN GA...WITH ADDITIONAL FOCI
FOR INCIPIENT CONVECTION EMANATING FROM SEA BREEZE CIRCULATIONS
FARTHER N TOWARD/OVER THE SC COASTAL PLAIN...WHICH WILL SPREAD
INLAND.

PER AREA VWP DATA...WEAK MID-LEVEL FLOW/DEEP SHEAR WILL LARGELY
MITIGATE CONVECTIVE ORGANIZATION...AND WEAK BACKGROUND LOW-LEVEL
FLOW WILL ASSIST IN KEEPING SFC GUSTS -- MOST LIKELY -- SUB-SEVERE.
HOWEVER...AN ISOLATED DMGG WIND GUST CANNOT BE RULED OUT WITH THE
MOST INTENSE STORMS OWING TO STRONG WATER LOADING...ESPECIALLY IN
AREAS OF LOCALIZED CONVECTIVE UPSCALE GROWTH WITH
MERGING/AGGREGATING COLD POOLS.

..COHEN/CORFIDI.. 08/21/2013

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

ATTN...WFO...ILM...CHS...CAE...MLB...TBW...JAX...FFC...TAE...

LAT...LON 26928238 27488277 29048322 30098414 30788427 31768356
34038075 34457968 34147904 33587900 32698010 31918156
30338259 28048166 27068182 26928238

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