MESOSCALE DISCUSSION 0196 NWS STORM PREDICTION CENTER NORMAN OK 0752 AM CDT MON MAR 17 2014 AREAS AFFECTED...THE CENTRAL FLORIDA PENINSULA CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE VALID 171252Z - 171515Z PROBABILITY OF WATCH ISSUANCE...60 PERCENT SUMMARY...THE RISK FOR SEVERE THUNDERSTORMS...INCLUDING TORNADOES...IS EXPECTED TO GRADUALLY INCREASE THIS MORNING. THIS MAY NECESSITATE THE ISSUANCE OF A TORNADO WATCH DURING THE NEXT COUPLE OF HOURS OR SO. DISCUSSION...A CORRIDOR OF DEEP CONVECTION HAS PERSISTED THROUGH MUCH OF THE NIGHT OVER THE EAST GULF/LOOP CURRENT INVOF A NE/SW-ORIENTED LOW-LEVEL CONFLUENCE AXIS WITHIN A WARM CONVEYOR IMPLIED BY OVERNIGHT MOISTURE-CHANNEL IMAGERY. SFC ANALYSIS REVEALS A QUASI-STATIONARY FRONT ROUGHLY ALIGNING WITH THIS ACTIVITY THAT EXTENDS FROM BROAD LOW PRESSURE IN THE MIDDLE GULF TO NRN FL. THETA-E DEFICITS OWING TO PERSISTENT CONVECTIVE OVERTURNING ROUGHLY N OF A LINE FROM CITRUS TO FLAGLER/VOLUSIA COUNTIES ARE REINFORCING THIS BOUNDARY. S OF THE BOUNDARY...POSITIVE MOISTURE ADVECTION IS SUPPORTING AN INFLUX OF MIDDLE-UPPER 60S DEWPOINTS AMIDST SFC-BASED EFFECTIVE INFLOW LAYERS PER 12Z TBW...MFL...AND KEY RAOBS. SLIGHTLY HIGHER DEWPOINTS LIE ALONG THE W FL COAST NEAR AND S OF TAMPA WHERE SOME ONSHORE FLOW COMPONENT OFF THE E GULF IS BREEDING AN INLAND MANIFESTATION OF LATENT HEAT FLUXES ATOP THE WARMER GULF WATERS. TBW VWP DATA INDICATE 50-65 KT OF SWLY/WSWLY FLOW IN THE 4-7-KM-AGL LAYER -- I.E. POSSESSING SOME /ALBEIT LIMITED/ COMPONENT ORTHOGONAL TO THE AMALGAMATION OF E-GULF MESO-BETA-SCALE CONVECTIVE ELEMENTS. THIS WILL CONTINUE TO FOSTER A GRADUAL NET EWD MOTION OF THE STRONGER CONVECTION TOWARD THE W FL COAST THROUGH THE MORNING. MEANWHILE...MODEST DIURNAL SFC-LAYER HEATING BENEATH THE MID/HIGH-LEVEL CLOUD CANOPY...SHED DOWNSTREAM OF ONGOING CONVECTION...WILL CONTRIBUTE TO CONTINUED DESTABILIZATION TO THE S OF THE AFOREMENTIONED SFC BOUNDARY. ALREADY...THE 12Z TBW RAOB INDICATES AROUND 1000 J/KG OF MLCAPE WITH NEGLIGIBLE MLCINH. THE JUXTAPOSITION OF THE PREVIOUSLY MENTIONED STRONG MID-LEVEL FLOW WITH A 35 KT LLJ SAMPLED BY THE TBW AND MLB VWP/S AND THE 12Z TBW RAOB WILL MAINTAIN THE POTENTIAL FOR ORGANIZED CONVECTION. CONVECTIVE MODE WILL LIKELY CONSIST OF QUASI-LINEAR SEGMENTS WITH EMBEDDED LEWP/BOWING STRUCTURES COMING OFF THE GULF WATERS AND SPREADING ACROSS THE CNTRL FL PENINSULA THROUGH THE DAY -- ESPECIALLY AFTER 1430Z. AS THE LLJ STRENGTHENS WITH THE APPROACH OF A SHORTWAVE IMPULSE ENTERING THE NW GULF...HIGH-MOMENTUM AIR JUST ABOVE THE SFC WILL FAVOR THE POTENTIAL FOR DAMAGING WIND GUSTS. FURTHERMORE...THE 12Z TBW RAOB ALREADY INDICATES AROUND 30 KT OF 0-1-KM SHEAR...AND THE MAGNITUDE OF SHEAR IN THIS LAYER SHOULD INCREASE AS THE LLJ STRENGTHENS. THIS WILL POTENTIALLY FOSTER LINE-EMBEDDED MESOVORTICES/POSSIBLE SUPERCELLS WITH TORNADOES. AT THIS TIME...THERE IS SOME UNCERTAINTY REGARDING THE TIMING OF INITIATION OF MORE ROBUST UPDRAFTS SUPPORTED BY INLAND DIURNAL DESTABILIZATION. VISIBLE SATELLITE IMAGERY SUGGESTS THAT CLOUDS COULD IMPEDE THIS PROCESS TO SOME EXTENT IN THE SHORT-TERM...THOUGH AT LEAST SOME GRADUAL INCREASE IN THE SVR POTENTIAL WILL OCCUR THROUGH THE MORNING. ..COHEN/EDWARDS.. 03/17/2014
Posted on: Mon, 17 Mar 2014 13:58:07 +0000
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