MESO: Mesoscale Discussion 0547

ACUS11 KWNS 211655
SWOMCD
SPC MCD 211654
FLZ000-211930-

MESOSCALE DISCUSSION 0547
NWS STORM PREDICTION CENTER NORMAN OK
1154 AM CDT SUN APR 21 2013

AREAS AFFECTED...PORTIONS CENTRAL/SRN FL.

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY

VALID 211654Z - 211930Z

PROBABILITY OF WATCH ISSUANCE...20 PERCENT

SUMMARY...SEA BREEZE CONVECTION FCST TO INCREASE IN
COVERAGE/INTENSITY...BECOMING NUMEROUS THIS AFTN PER SPC ENHANCED
TSTM OUTLOOK. MAIN THREAT WILL BE ISOLATED DAMAGING
DOWNDRAFTS...WITH MRGL SVR HAIL ALSO POSSIBLE. FOCI FOR LOCALLY
ENHANCED RISK SHOULD BE INVOF OUTFLOW-OUTFLOW AND OUTFLOW-SEA BREEZE
BOUNDARY INTERSECTIONS. ATTM...POTENTIAL ORGANIZATION/COVERAGE
APPEARS TOO LOW FOR WW.

DISCUSSION...16Z SFC MESOANALYSIS INDICATES WEAKENING/ORIGINAL
SYNOPTIC FRONT IS QUASISTATIONARY OVER SRN FL...ACROSS PORTIONS PALM
BEACH/HENDRY/COLLIER COUNTIES...AND MAINLY IS MANIFEST AS WIND SHIFT
LINE AWAY FROM SEA BREEZE/OUTFLOW BOUNDARIES. SECOND/STRONGER
BAROCLINIC ZONE...WHICH ALSO WAS EVIDENT IN 12Z 925-MB
ANALYSIS...HAS BECOME BETTER EVIDENT AT SFC AMIDST DIFFERENTIAL
DIABATIC HEATING AND DEEP ELYS TO ITS S. LATTER FRONTAL ZONE WAS
LOCATED NEAR I-4 CORRIDOR DAB-TBW AND MAY DRIFT NWWD. VIS IMAGE
LOOPS AND SFC DATA INDICATE OUTFLOW BOUNDARIES FROM EARLIER
CONVECTION OVER GULF STREAM HAS EFFECTIVELY BOWED SEA BREEZE
BOUNDARY INLAND FROM NRN ST LUCIE INTO ERN OSCEOLA COUNTIES...AS
WELL AS OVER SRN PALM BEACH...CENTRAL BROWARD AND NRN MIAMI-DADE
COUNTIES. CONVECTION ALREADY HAS FORMED ALONG THAT BOUNDARY OVER
INTERIOR BROWARD/MIAMI-DADE COUNTY LINE...WITH ADDITIONAL TSTMS
EXPECTED FARTHER N UP E COAST SEA BREEZE IN NEXT 2-3 HOURS.

PW S OF NRN FRONT AND INLAND FROM SEA BREEZES COMMONLY IS IN
1.5-1.75 INCH RANGE AND LOCALLY GREATER...BASED ON GPS-PW
READINGS...MODIFIED RAOBS AND FCST SOUNDINGS. CONTINUED DIABATIC
HEATING IN MOISTURE-RICH/PRECONVECTIVE/INLAND AIR MASS ALREADY IS
RAISING 0-3 KM CAPE SUBSTANTIALLY AND REMOVING CINH...AND SHOULD
BOOST MLCAPE INTO 1500-2000 J/KG RANGE AWAY FROM TSTMS/OUTFLOW.
THIS...ALONG WITH DEPTH OF BUOYANT LAYER IN SOUNDINGS...INDICATES
POTENTIAL FOR LOCALLY STG PRECIP LOADING AND RELATED RISK FOR
DOWNBURSTS NEAR SVR LEVELS AND CAPABLE OF CAUSING DAMAGE.
KINEMATICALLY...WEAK/CHAOTIC 0-3 KM AGL FLOW YIELDS WEAK LOW-LEVEL
SHEAR FROM VWP. HOWEVER...STG UPPER/ANVIL-LEVEL WINDS IN MORNING
RAOBS AND FCST SOUNDINGS SUGGESTS ENHANCED CONVECTIVE VENTILATION
ALOFT AND RELATED CONTRIBUTION TO STORM MAINTENANCE/ORGANIZATION.

..EDWARDS/MEAD.. 04/21/2013

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

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

LAT...LON 28368080 27188023 26718031 26298044 25868043 25498040
25238058 25308083 25668112 25968162 26148180 26428188
26418204 26508219 26888230 27288255 27638258 28098159
28458091 28368080

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