000 WTNT41 KNHC 292031 TCDAT1 TROPICAL STORM KIRK DISCUSSION NUMBER 5 NWS NATIONAL HURRICANE CENTER MIAMI FL AL112012 500 PM AST WED AUG 29 2012 DEEP CONVECTION HAS BLOSSOMED OVER THE CENTER OF KIRK THIS AFTERNOON...BUT CLOUD TOP TEMPERATURES HAVE BEGUN TO WARM AGAIN OVER THE PAST HOUR OR SO. THE INITIAL INTENSITY IS SET TO 45 KT BASED ON THE LATEST DVORAK ESTIMATES FROM TAFB AND SAB. IN THE SHORT TERM...MODERATE SHEAR VALUES AND SOME DRY AIR IN THE ENVIRONMENT WOULD SEEM TO SUPPORT ONLY GRADUAL STRENGTHENING IN THE NEXT DAY OR SO. BEYOND 36 HOURS...THE SHEAR IS EXPECTED TO DECREASE AS KIRK MOVES AROUND THE WESTERN SIDE OF THE SUBTROPICAL RIDGE... AND MOST OF THE GUIDANCE SHOWS KIRK BECOMING A HURRICANE BY 72 HOURS. WEAKENING IS EXPECTED BY DAY 4 AS THE SHEAR INCREASES DRAMATICALLY AND KIRK MOVES OVER COOLER WATERS BEFORE THE CYCLONE IS ABSORBED BY DAY 5. THROUGH THE PERIOD THE NHC FORECAST IS CLOSE TO THE VARIOUS INTENSITY CONSENSUS AIDS. THE CENTER NOW APPEARS TO BE EMBEDDED UNDER THE DEEP CONVECTION AND IS ABOUT A HALF A DEGREE TO THE RIGHT OF THE PREVIOUS FORECAST. THE INITIAL MOTION ESTIMATE IS A RATHER UNCERTAIN 300/09. OVERALL THE TRACK FORECAST REASONING REMAINS UNCHANGED...AS KIRK WILL MOVE AROUND THE WESTERN SIDE OF THE SUBTROPICAL RIDGE IN THE NEXT 24 HOURS AND THEN BEGIN TO ACCELERATE NORTHWARD AND NORTHEASTWARD AS THE CYCLONE RECURVES AHEAD OF AN AMPLIFYING MID-LATITUDE TROUGH. MOST OF THE GUIDANCE HAS SHIFTED TOWARD A SHARPER RECURVATURE THIS CYCLE WITH A FASTER FORWARD SPEED LATE IN THE PERIOD. FOR EXAMPLE...THE ECMWF...WHICH WAS ON THE LEFT SIDE OF THE GUIDANCE ENVELOPE EARLIER NOW LIES CLOSER TO THE MIDDLE OF THE ENVELOPE BUT IS EAST OF THE CONSENSUS. OVERALL THE MODEL CONSENSUS HAS SHIFTED RIGHTWARD THIS CYCLE...AND THIS...IN COMBINATION WITH THE ADJUSTMENT IN THE INITIAL POSITION AND MOTION...RESULTS IN A RIGHTWARD SHIFT OF ABOUT A DEGREE IN THE NHC TRACK IN THE FIRST 36 HOURS. BEYOND THAT TIME...THE NHC FORECAST IS BLENDED BACK TOWARD THE OLD TRACK...BUT IS FASTER. THROUGHOUT THE PERIOD THE NHC TRACK IS NEAR THE TVCA CONSENSUS. FORECAST POSITIONS AND MAX WINDS INIT 29/2100Z 25.3N 47.6W 45 KT 50 MPH 12H 30/0600Z 26.1N 48.9W 50 KT 60 MPH 24H 30/1800Z 27.7N 50.4W 50 KT 60 MPH 36H 31/0600Z 29.6N 51.3W 55 KT 65 MPH 48H 31/1800Z 31.9N 51.1W 60 KT 70 MPH 72H 01/1800Z 38.0N 46.0W 70 KT 80 MPH 96H 02/1800Z 45.5N 37.0W 60 KT 70 MPH 120H 03/1800Z...ABSORBED $$ FORECASTER BRENNAN