ZCZC MIATCDAT4 ALL TTAA00 KNHC DDHHMM TROPICAL STORM SEAN DISCUSSION NUMBER 6 NWS NATIONAL HURRICANE CENTER MIAMI FL AL192011 1000 AM EST WED NOV 09 2011 DURING THE PAST FEW HOURS...CONVECTION HAS BECOME BETTER ORGANIZED IN A BROKEN RING AROUND THE CENTER OF SEAN...WITH THE POSSIBILITY THAT AN EYE FEATURE IS FORMING. SUBJECTIVE SATELLITE INTENSITY ESTIMATES FROM TAFB/SAB ARE 45/55 KT...AND A BLEND OF THESE DATA GIVES AN INITIAL WIND SPEED OF 50 KT. SEAN HAS ABOUT 24 TO 36 HOURS OF RELATIVELY LOW SHEAR CONDITIONS...WHICH WOULD SEEM TO FAVOR SOME INTENSIFICATION. MODEL GUIDANCE IS A BIT HIGHER...AND THE OFFICIAL WIND SPEED FORECAST IS RAISED FROM THE LAST ONE... BETWEEN THE STATISTICAL MODELS AND THE INTENSITY CONSENSUS. THE OFFICIAL FORECAST MIGHT BE CONSERVATIVE IF A CENTRAL CORE BECOMES WELL ESTABLISHED. THE GRADUAL POLEWARD TURN OF THE CYCLONE HAS BEGUN...WITH AN INITIAL MOTION ESTIMATE OF 320/3. SHORTWAVE RIDGING OVER THE WESTERN ATLANTIC WILL MOVE TO THE EAST LATER TODAY...STEERING SEAN ON A PATH TOWARD THE NORTH AND NORTH-NORTHEAST BY EARLY TOMORROW. AS A TROUGH OVER THE EASTERN UNITED STATES APPROACHES THE STORM...AN INCREASE IN MID-TROPOSPHERIC FLOW SHOULD CAUSE THE TROPICAL CYCLONE TO ACCELERATE NORTHEASTWARD. THERE CONTINUES TO BE A FAIR AMOUNT OF SPREAD...HOWEVER...ON HOW FAR SEAN MOVES FROM BERMUDA. THE GFS AND ECMWF HAVE BEEN MORE CONSISTENT THAN THE REST OF THE GUIDANCE SHOWING A CLOSER TRACK TO BERMUDA...SO THE OFFICIAL FORECAST WILL STAY NEAR THOSE HISTORICALLY RELIABLE MODELS. MOST OF THE GLOBAL MODELS SHOW THIS SYSTEM BEING ABSORBED WITHIN A FRONT BETWEEN DAY 3 AND DAY 4...AND THE NHC FORECAST CONTINUES TO FOLLOW THIS SCENARIO. FORECAST POSITIONS AND MAX WINDS INIT 09/1500Z 27.9N 70.5W 50 KT 60 MPH 12H 10/0000Z 28.4N 70.6W 55 KT 65 MPH 24H 10/1200Z 29.6N 70.2W 55 KT 65 MPH 36H 11/0000Z 31.5N 68.4W 55 KT 65 MPH 48H 11/1200Z 33.8N 65.3W 50 KT 60 MPH 72H 12/1200Z 41.0N 53.0W 45 KT 50 MPH...POST-TROP/EXTRATROP 96H 13/1200Z...ABSORBED $$ FORECASTER BLAKE NNNN
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