[Tropical] Tropical Cyclone Discussion

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WTNT44 KNHC 100240
TCDAT4

TROPICAL STORM SEAN DISCUSSION NUMBER   8
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL192011
1000 PM EST WED NOV 09 2011

RECENT SATELLITE TRENDS SUGGEST THAT THE INTENSITY OF SEAN HAS
LEVELED OFF THIS EVENING. CLOUD TOP TEMPERATURES NEAR THE CENTER
HAVE WARMED...ALTHOUGH RECENT MICROWAVE IMAGERY FROM THE U.S. NAVY
FNMOC TC WEBPAGE STILL SHOWS A BANDING EYE FEATURE. BASED ON DVORAK
CURRENT INTENSITY ESTIMATE FROM TAFB AND SAB...THE INITIAL
INTENSITY REMAINS 55 KT. GIVEN THE CONTINUED PRESENCE OF SOME INNER
CORE STRUCTURE...SEAN STILL HAS AN OPPORTUNITY TO STRENGTHEN IN THE
NEXT 12 TO 24 HOURS BEFORE VERTICAL WIND SHEAR INCREASES. THE NHC
INTENSITY FORECAST REMAINS UNCHANGED FROM THE PREVIOUS ADVISORY AND
IS A LITTLE ABOVE THE LGEM AT 24 HOURS...SHOWING SEAN REACHING
HURRICANE STRENGTH. AFTER THAT TIME...SEAN SHOULD WEAKEN DUE TO
COOLER WATERS AND INCREASING SHEAR. MODEL FIELDS SHOW THE CYCLONE
BECOMING EXTRATROPICAL BY 48 HOURS AND BEING ABSORBED BY A FRONTAL
BOUNDARY SHORTLY THEREAFTER...BUT THIS COULD OCCUR EVEN SOONER.

SEAN HAS JOGGED QUICKLY NORTHWARD THIS EVENING...AND THE INITIAL
MOTION ESTIMATE IS 360/07. SEAN SHOULD TURN NORTHEASTWARD ON
THURSDAY FOLLOWED BY A STEADY INCREASE IN FORWARD SPEED THURSDAY
NIGHT AND FRIDAY AS THE CYCLONE BECOMES EMBEDDED IN THE
SOUTHWESTERLY FLOW AHEAD OF A TROUGH MOVING OFF OF THE EAST COAST
OF THE UNITED STATES. THE NEW NHC FORECAST IS A LITTLE FASTER AND A
LITTLE TO THE LEFT OF THE PREVIOUS ONE IN THE FIRST 12 TO 24 HOURS
DUE TO THE FASTER NORTHWARD MOTION THIS EVENING. AFTER THAT TIME
ONLY MINOR CHANGES WERE MADE TO THE OFFICIAL FORECAST...WHICH
REMAINS CLOSE TO THE GFS AND ECMWF MODELS UNTIL DISSIPATION.


FORECAST POSITIONS AND MAX WINDS

INIT  10/0300Z 29.5N  70.7W   55 KT  65 MPH
 12H  10/1200Z 30.3N  70.2W   60 KT  70 MPH
 24H  11/0000Z 31.8N  68.3W   65 KT  75 MPH
 36H  11/1200Z 34.5N  64.9W   55 KT  65 MPH
 48H  12/0000Z 38.5N  59.3W   45 KT  50 MPH...POST-TROP/EXTRATROP
 72H  13/0000Z...ABSORBED BY FRONT

$$
FORECASTER BRENNAN


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