MESO: Mesoscale Discussion 1817

ACUS11 KWNS 270244
SWOMCD
SPC MCD 270244
FLZ000-270445-

MESOSCALE DISCUSSION 1817
NWS STORM PREDICTION CENTER NORMAN OK
0944 PM CDT SUN AUG 26 2012

AREAS AFFECTED...SRN FLORIDA

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 270244Z - 270445Z

PROBABILITY OF WATCH ISSUANCE...60 PERCENT

SUMMARY...IT IS NOT YET CERTAIN THAT A TORNADO WATCH WILL BE NEEDED
THIS EVENING/OVERNIGHT...BUT TRENDS ARE BEING MONITORED FOR A
CONTINUED INCREASE IN SEVERE POTENTIAL THAT COULD POSSIBLY REQUIRE
ONE.

DISCUSSION...WITH TROPICAL STORM ISAAC TAKING A GRADUAL TURN TO THE
NORTHWEST AS IT PROGRESSES WEST OF THE LOWER KEYS INTO THE
SOUTHEASTERN GULF OF MEXICO...LOW-LEVEL FLOW FIELDS HAVE VEERED
SOME...TO A MORE SOUTHERLY COMPONENT...ACROSS SOUTHERN
FLORIDA...WITH SOME STRENGTHENING TO 50+ KT IN THE LOWEST 1-2 KM
EVIDENT IN VAD WIND PROFILER DATA. THIS HAS COINCIDED WITH
INTENSIFICATION OF CONVECTIVE BANDS...AS REFLECTED BY
EXPANDING/COOLING CLOUD TOPS AND INCREASING CLOUD TO GROUND
LIGHTNING...ON THE OUTER PERIPHERY OF ISAAC...ACROSS COASTAL AREAS
NEAR/NORTH OF MIAMI...INTO THE INTERIOR SOUTH CENTRAL PENINSULA.
ALTHOUGH LATEST OBJECTIVE ANALYSES SUGGEST THAT APPRECIABLE BOUNDARY
LAYER INSTABILITY REMAINS CONFINED TO THE MORE IMMEDIATE SOUTHEAST
COASTAL AREAS...POTENTIAL APPEARS TO EXIST FOR THE INLAND ADVECTION
OF A MORE MOIST/DEEPER BOUNDARY LAYER OVERNIGHT...AS LOW-LEVEL WINDS
CONTINUE TO VEER TO THE SOUTH. IF THIS OCCURS...IN THE PRESENCE OF
CONTINUING STRONG LOW-LEVEL SHEAR...IT MAY NOT BE OUT OF THE
QUESTION THAT THE POTENTIAL COULD INCREASE FOR THE DEVELOPMENT OF
SUPERCELLS CAPABLE OF PRODUCING TORNADOES.

..KERR/CORFIDI.. 08/27/2012

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

ATTN...WFO...MFL...MLB...TBW...

LAT...LON 27158244 27358161 27138024 26478007 25618016 25488045
25498112 26048177 26468190 27158244

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