DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 261221
SWODY1
SPC AC 261219

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0719 AM CDT SUN AUG 26 2012

VALID 261300Z - 271200Z

...THERE IS A SLGT RISK OF SVR TSTMS SOUTH AND CNTRL FL PENINSULA
AND THE FL KEYS...

...SYNOPSIS...
THE CENTER OF STRENGTHENING TROPICAL STORM ISAAC IS FORECAST TO
TRACK WNWWD TO NWWD ACROSS THE STRAITS OF FL AND MOVE NEAR OR OVER
THE FL KEYS LATER TODAY AND TONIGHT BEFORE EMERGING INTO THE ERN
GULF OF MEXICO. ISAAC IS FORECAST TO BECOME A HURRICANE BY MONDAY
MORNING. PLEASE REFERENCE THE LATEST FORECAST/ADVISORY PACKAGE FROM
THE NATIONAL HURRICANE CENTER FOR ADDITIONAL DETAILS. ELSEWHERE...A
MID-LEVEL VORT MAX WILL SLOWLY MOVE NEWD ACROSS THE MID-ATLANTIC...
WHILE A POSITIVELY TILTED TROUGH COVERS THE MID-SECTION OF THE
COUNTRY.

...SOUTH AND CNTRL FL PENINSULA AND THE FL KEYS...
AS THE NORTHEAST QUADRANT OF ISAAC CROSSES PARTS OF THE FL PENINSULA
AND THE FL KEYS...LOW-LEVEL CURVED HODOGRAPHS WILL ELONGATE.
OBSERVED MIAMI/KEY WEST RAOBS DURING THE PAST 12 HOURS HAVE ALREADY
INDICATED A STEADY RAMP-UP OF SRH LAST NIGHT...AND THIS WILL
CONTINUE THROUGH THE DAY AS THE STRONGER WIND FIELD AROUND ISAAC
NEARS. WITH A GRADIENT IN THE MAGNITUDE OF LOW-LEVEL SRH ORIENTED
SWD ACROSS THE PENINSULA...THE LATEST FORECAST SOUNDINGS ARE IN
AGREEMENT THAT UPWARDS OF AROUND 500 M2/S2 EFFECTIVE SRH WILL
OVERLAY SOUTH FL AND THE KEYS BY THIS AFTERNOON.

BOUNDARY-LAYER HEAT CONTENT WITHIN THE NERN QUADRANT OF ISAAC IS
EXPECTED TO BE SUPPORTED BY...
/1/ MOIST TRAJECTORIES SUBJECTED TO OCEANIC HEAT FLUXES ATOP 29-30C
SST/S OVER THE SW N ATLC...
/2/ ANTICIPATED POCKETS OF INSOLATION/DIABATIC HEATING ASSOCIATED
WITH THE INFLUENCE OF DRY AIR SAMPLED BY THE 06Z MIAMI RAOB AND
WATER VAPOR IMAGERY IN THE WAKE OF A LEAD WAVE.
AND...WITH RICH DEEP MOISTURE WITH SFC DEWPOINTS IN THE MIDDLE
70S...MODIFIED FORECAST SOUNDINGS INDICATE 1000-1500 J/KG OF MLCAPE
LIKELY BECOMING JUXTAPOSED WITH THE AFOREMENTIONED STRONG SRH.

CONSISTENT WITH THE CONSENSUS AMONGST CONVECTION-ALLOWING MODEL
GUIDANCE...MULTIPLE FEEDER BANDS WILL PIVOT AROUND THE NERN QUADRANT
OF ISAAC THROUGH MUCH OF TODAY AND INTO TONIGHT. GIVEN THE STRONG
SRH AND POTENTIALLY MODERATE INSTABILITY...EMBEDDED TORNADIC
SUPERCELLS ARE POSSIBLE WITH THE FEEDER BANDS...WITH ADDITIONAL
DISCRETE SUPERCELLS ALSO POSSIBLE DISPLACED FROM THE CORE OF ISAAC.
THE THREAT FOR TORNADOES WILL EXPAND NWD ACROSS THE FL PENINSULA
THROUGH THE PERIOD GIVEN THE ANTICIPATED TRACK OF ISAAC. THE MOST
FAVORABLE ENVIRONMENT FOR TORNADOES...AND MOST PROLONGED DURATION OF
THIS ENVIRONMENT...WILL EXIST OVER SOUTH FL AND THE FL KEYS...WHERE
TORNADO PROBABILITIES HAVE BEEN INCREASED WITHIN THE SLIGHT RISK
CATEGORY.

PLEASE REFERENCE MCD NUMBER 1813 FOR ADDITIONAL NEAR-TERM CONVECTIVE
TRENDS.

...MID-ATLANTIC REGION...
THE MID-ATLANTIC VORT MAX IS ACCOMPANIED BY A WEAK SFC WAVE AND
MODESTLY UNSTABLE SECTOR EXTENDING INLAND. LOW THREATS FOR A SVR
WIND GUST OR TWO AND PERHAPS A WEAK TORNADO WILL EXIST WITH
REGENERATING CONVECTION WITHIN THE UNSTABLE SECTOR AS FORECAST
SOUNDINGS DEPICT SOME LOW-LEVEL DIRECTIONAL SHEAR. HOWEVER...WEAK
MID-LEVEL FLOW AND WEAK MID-LEVEL LAPSE RATES WILL BE THE MAIN
INHIBITORS FOR A GREATER SVR THREAT.

...FAR ERN OK NEWD INTO CNTRL IL...
MLCAPE OF 700-1100 J/KG EAST OF A CONVECTIVELY REINFORCED BOUNDARY
ATTENDANT TO THE POSITIVELY TILTED TROUGH WILL BE AIDED BY UPPER
60S-NEAR 70F SFC DEWPOINTS AND POCKETS OF INSOLATION. MODEST DEEP
SHEAR SUPPORTED BY 20-25 KT OF MID-LEVEL FLOW MAY YIELD A FEW
MULTICELL CLUSTERS WITH SPORADIC STRONG/SVR WIND GUSTS. HOWEVER...
WEAK MID-LEVEL LAPSE RATES WILL GREATLY MITIGATE THE SVR THREAT.

...CNTRL HIGH PLAINS...
LOW-LEVEL ASCENT WITH A SFC LEE TROUGH MAY BE SUFFICIENT FOR
ISOLATED THUNDERSTORM DEVELOPMENT THIS AFTERNOON. WITH 20-35 KT OF
DEEP SHEAR AMIDST MARGINAL INSTABILITY...A CONDITIONAL THREAT FOR
ORGANIZED/LOCALLY SVR STORMS CANNOT BE RULED OUT WITH STRONG
WINDS/HAIL. LIMITED FORCING FOR ASCENT AND LIMITED LOW-LEVEL
MOISTURE WILL BE THE MAIN INHIBITORS FOR A MORE SUBSTANTIAL SVR
THREAT.

..COHEN/THOMPSON/EDWARDS.. 08/26/2012

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