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#633097 (Received by flhurricane at: 4:44 PM 18.Sep.2013) TCDAT4 TROPICAL STORM HUMBERTO DISCUSSION NUMBER 34 NWS NATIONAL HURRICANE CENTER MIAMI FL AL092013 500 PM AST WED SEP 18 2013 CONVECTION HAS INCREASED A LITTLE NEAR THE CENTER OF HUMBERTO... MAINLY IN SKELETAL BANDS IN THE NORTHEASTERN SEMICIRCLE. WATER VAPOR AND AIRMASS IMAGERY SHOWS THAT THE LOW-LEVEL CENTER IS STILL IN CLOSE PROXIMITY TO AN UPPER-LEVEL LOW...AND THIS MAY BE SLOWING THE DEVELOPMENT OF THE CENTRAL CONVECTION. RECENT OSCAT DATA SHOWED A FEW 30-35 KT WIND VECTORS ABOUT 150 N MI FROM THE CENTER IN THE EASTERN SEMICIRCLE. IN ADDITION...RECENT AMSU INTENSITY ESTIMATES FROM CIRA AND CIMSS ARE 37 KT AND 32 KT RESPECTIVELY. BASED ON THESE DATA...THE INITIAL INTENSITY REMAINS A POSSIBLY GENEROUS 35 KT. HUMBERTO HAS MADE ITS EXPECTED NORTHWARD TURN WITH THE INITIAL MOTION NOW 355/5. THE SYSTEM IS EXPECTED TO CONTINUE NORTHWARD DURING THE NEXT 12 HOURS OR SO...FOLLOWED BY AN ACCELERATION TOWARD THE NORTH-NORTHEAST AS THE CYCLONE ENTERS THE WESTERLIES. THE TRACK MODEL GUIDANCE REMAINS TIGHTLY CLUSTERED...AND THE NEW TRACK FORECAST IS AGAIN SIMILAR TO THE PREVIOUS FORECAST. THERE IS STILL TIME FOR HUMBERTO TO STRENGTHEN SOME AS IT MOVES INTO A MORE FAVORABLE UPPER-LEVEL WIND ENVIRONMENT NORTH OF THE UPPER-LEVEL LOW. THE CYCLONE SHOULD APPROACH A FRONTAL ZONE IN 36-48 HOURS. HOWEVER...THE MODELS ARE IN POOR AGREEMENT ON WHETHER HUMBERTO WILL UNDERGO EXTRATROPICAL TRANSITION...OR WHETHER IT WILL DEGENERATE TO A TROUGH AS ANOTHER LOW BECOMES THE PREDOMINANT SYSTEM. THE INTENSITY FORECAST FOLLOWS THE PREVIOUS FORECAST IN CALLING FOR HUMBERTO TO BECOME EXTRATROPICAL IN 48 HOURS. THAT BEING SAID...REGARDLESS OF THE EXACT EVOLUTION THERE IS LIKELY TO BE A STORM-FORCE EXTRATROPICAL LOW NEAR THE 72 HOUR POINT. FORECAST POSITIONS AND MAX WINDS INIT 18/2100Z 31.8N 43.7W 35 KT 40 MPH 12H 19/0600Z 33.0N 43.6W 35 KT 40 MPH 24H 19/1800Z 34.9N 42.9W 40 KT 45 MPH 36H 20/0600Z 37.4N 41.0W 40 KT 45 MPH 48H 20/1800Z 41.6N 37.1W 45 KT 50 MPH...POST-TROP/EXTRATROP 72H 21/1800Z 54.0N 23.5W 50 KT 60 MPH...POST-TROP/EXTRATROP 96H 22/1800Z...ABSORBED BY EXTRATROPICAL LOW $$ FORECASTER BEVEN |