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#39923 (Received by flhurricane at: 10:31 PM 15.Aug.2005) TCDAT4 HURRICANE IRENE DISCUSSION NUMBER 46 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 11 PM EDT MON AUG 15 2005 THE CENTER HAS BEEN MOSTLY INDISTINCT ON SATELLITE IMAGERY THIS EVENING...AND AN SSMI OVERPASS AT 23Z SHOWED THE EYEWALL HAS ERODED SLIGHTLY COMPARED TO THIS MORNING. HOWEVER...DVORAK INTENSITY ESTIMATES ARE UNCHANGED AND I WILL LEAVE THE ADVISORY INTENSITY AT 80 KT. THERE IS CURRENTLY NO OUTFLOW IN THE NORTHWEST QUADRANT AS IRENE IS BEGINNING TO BE AFFECTED BY THE UPPER-LEVEL WESTERLIES. BASED LARGELY ON THAT SSMI OVERPASS...THE INITIAL MOTION IS ESTIMATED TO BE 085/12...FASTER THAN BEFORE...AND FASTER THAN PREDICTED BY THE 18Z GUIDANCE MODELS. IN ADDITION...MUCH OF THE CURRENT GUIDANCE IS SIGNIFICANTLY SLOWER THAN THE PREVIOUS OFFICIAL FORECAST. GIVEN THE CURRENT ACCELERATION TREND...I WILL ONLY SLOW THE PREVIOUS FORECAST A LITTLE BIT AND THE NEW FORECAST IS FAIRLY CLOSE TO THE FSU SUPERENSEMBLE. SHOULD IRENE TAKE A PATH FARTHER SOUTH THAN EXPECTED...IT COULD MOVE QUITE A BIT SLOWER THAN FORECAST. IRENE STILL HAS ABOUT 36 HOURS OVER WARM WATER...BUT THE SHEAR IS EXPECTED TO INCREASE BEFORE THEN. THIS SHEAR SHOULD INDUCE A WEAKENING TREND...AND INDEED THE MICROWAVE DATA SUGGEST THIS TREND HAS ALREADY BEGUN. WEAKENING WOULD LIKELY BE SLOWER THAN FORECAST SHOULD IRENE TAKE A MORE SOUTHERLY TRACK. COOLER WATERS AND AN APPROACHING MID-LATITUDE TROUGH ARE EXPECTED TO RESULT IN AN EXTRATROPICAL TRANSITION WITHIN ABOUT 48 HOURS. FORECASTER FRANKLIN FORECAST POSITIONS AND MAX WINDS INITIAL 16/0300Z 36.6N 64.4W 80 KT 12HR VT 16/1200Z 37.1N 62.4W 75 KT 24HR VT 17/0000Z 38.2N 59.8W 65 KT 36HR VT 17/1200Z 40.4N 56.3W 55 KT 48HR VT 18/0000Z 43.5N 51.5W 50 KT...EXTRATROPICAL 72HR VT 19/0000Z 52.0N 40.0W 45 KT...EXTRATROPICAL 96HR VT 20/0000Z 58.0N 32.0W 40 KT...EXTRATROPICAL 120HR VT 21/0000Z...ABSORBED INTO EXTRATROPICAL LOW |