000 WTNT44 KNHC 100836 TCDAT4 TROPICAL STORM SEAN DISCUSSION NUMBER 9 NWS NATIONAL HURRICANE CENTER MIAMI FL AL192011 400 AM EST THU NOV 10 2011 INFRARED AND MICROWAVE SATELLITE IMAGERY THIS MORNING SHOWS THAT SEAN IS SLOWLY BECOMING BETTER ORGANIZED...WITH INCREASING CONVECTIVE BANDING AROUND THE CENTER AND OCCASIONAL ATTEMPTS AT EYE FORMATION. SATELLITE INTENSITY ESTIMATES FROM SAB AND TAFB ARE 55 KT...AND THAT REMAINS THE INITIAL INTENSITY. THE CYCLONE CURRENTLY HAS GOOD CIRRUS OUTFLOW IN THE NORTH SEMICIRCLE. SEAN CONTINUES ITS NORTHERLY TRACK WITH AN INITIAL MOTION OF 355/7. WATER VAPOR IMAGERY SHOWS SOUTHWESTERLY MID/UPPER-LEVEL FLOW ASSOCIATED WITH A TROUGH OVER THE EASTERN UNITED STATES APPROACHING THE CYCLONE...AND THE GUIDANCE IS IN GOOD AGREEMENT THAT THIS SHOULD CAUSE SEAN TO TURN NORTHEASTWARD IN THE NEXT 12 HOURS. AFTER THAT...THE CYCLONE SHOULD ACCELERATE NORTHEASTWARD DURING THE REMAINDER OF ITS LIFETIME. THE NEW FORECAST TRACK FOLLOWS THIS SCENARIO AND IS SIMILAR TO...BUT NORTH OF...THE PREVIOUS TRACK. THE FORECAST TRACK IS NEAR THE CENTER OF THE TRACK GUIDANCE ENVELOPE. THERE IS PERHAPS 12-24 HOURS FOR SEAN TO STRENGTHEN BEFORE STRONG VERTICAL WIND SHEAR IMPACTS THE STORM. GIVEN THE CURRENT STRUCTURE...THE INTENSITY FORECAST CALLS FOR SEAN TO REACH HURRICANE STRENGTH IN 24 HOURS IN AGREEMENT WITH THE PREVIOUS FORECAST. AFTER THAT...STRONG SHEAR AND THE START OF EXTRATROPICAL TRANSITION SHOULD CAUSE WEAKENING. EXTRATROPICAL TRANSITION IS EXPECTED TO BE COMPLETE BY 48 HOURS...AND BY 72 HOURS SEAN IS EXPECTED TO BE ABSORBED BY A LARGER BAROCLINIC SYSTEM TO ITS NORTH. AS NOTED IN THE PREVIOUS DISCUSSION...IT IS POSSIBLE THAT SEAN COULD DISSIPATE EARLIER THAN CURRENTLY FORECAST. FORECAST POSITIONS AND MAX WINDS INIT 10/0900Z 30.2N 70.9W 55 KT 65 MPH 12H 10/1800Z 31.2N 69.8W 60 KT 70 MPH 24H 11/0600Z 33.4N 67.2W 65 KT 75 MPH 36H 11/1800Z 37.0N 63.0W 55 KT 65 MPH 48H 12/0600Z 41.5N 56.5W 45 KT 50 MPH...POST-TROP/EXTRATROP 72H 13/0600Z...ABSORBED BY EXTRATROPICAL LOW $$ FORECASTER BEVEN