ZCZC MIATCDAT4 ALL TTAA00 KNHC DDHHMM TROPICAL STORM SEAN DISCUSSION NUMBER 12 NWS NATIONAL HURRICANE CENTER MIAMI FL AL192011 1100 PM AST THU NOV 10 2011 SATELLITE TRENDS HAVE PROVIDED MIXED SIGNALS REGARDING THE INTENSITY OF SEAN OVER THE PAST FEW HOURS. ON ONE HAND...VERTICAL SHEAR OF ABOUT 20 KT AS ANALYZED BY UW-CIMSS HAS DISPLACED THE MID-LEVEL CENTER EAST OF THE LOW-LEVEL CENTER...AS SEEN IN RECENT MICROWAVE IMAGERY FROM THE FNMOC TC WEBPAGE. HOWEVER...CONVECTIVE CLOUD TOPS HAVE COOLED AND EXPANDED IN COVERAGE OVER THE PAST FEW HOURS. THEREFORE...THE INITIAL INTENSITY WILL BE HELD AT 55 KT IN AGREEMENT WITH 00Z DVORAK CI-NUMBERS FROM TAFB AND SAB. THE NHC FORECAST SHOWS NO CHANGE IN INTENSITY DURING THE NEXT 12 HOURS...IN AGREEMENT WITH MOST OF THE GUIDANCE. BY 24 HOURS...SEAN SHOULD BE ABSORBED BY THE FRONTAL BOUNDARY NOW MOVING OFFSHORE OF THE EAST COAST OF THE UNITED STATES. RECENT DVORAK AND MICROWAVE FIXES SUGGEST THAT THE LOW-LEVEL CENTER HAS BEEN MOVING A BIT TO THE RIGHT OF THE PREVIOUS FORECAST...WITH AN INITIAL MOTION OF 060/11. THIS RIGHTWARD JOG SHOULD BE TEMPORARY HOWEVER...AS ALL OF THE GUIDANCE SHOWS A NORTHEASTWARD MOTION DEVELOPING OVERNIGHT AS THE DEEP-LAYER FLOW BECOMES SOUTHWESTERLY AHEAD OF THE MID/UPPER-LEVEL TROUGH MOVING OFF THE U.S. EAST COAST. GIVEN THE INITIAL POSITION AND MOTION...THE NEW NHC TRACK FORECAST HAS BEEN ADJUSTED TO THE RIGHT...OR SOUTHEAST...OF THE PREVIOUS ONE...AND LIES A LITTLE TO THE RIGHT OF THE GFS AND ECMWF AND CLOSE TO THE GEFS ENSEMBLE MEAN. FORECAST POSITIONS AND MAX WINDS INIT 11/0300Z 31.5N 68.2W 55 KT 65 MPH 12H 11/1200Z 33.6N 65.3W 55 KT 65 MPH 24H 12/0000Z...ABSORBED BY FRONT $$ FORECASTER BRENNAN NNNN
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Page last modified: Tuesday, 17-Jul-2012 13:44:10 UTC