Tropical Storm HANNA

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TROPICAL STORM HANNA DISCUSSION NUMBER  41
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL082008
1100 PM EDT SAT SEP 06 2008
 
THE CENTER OF HANNA IS MOVING OVER THE WEST-CENTRAL PORTION OF LONG
ISLAND. THE INITIAL MOTION ESTIMATE IS 050/26...AND HANNA IS RIGHT
ON TRACK. GRADUAL ACCELERATION IS FORECAST DURING THE NEXT 48 HOURS
AS HANNA GETS CAUGHT UP IN THE FAST UPPER-LEVEL WESTERLIE...AND THE
NEW NHC MODEL GUIDANCE IS TIGHTLY CLUSTERED ABOUT THE PREVIOUS
FORECAST TRACK. THEREFORE...NO SIGNIFICANT CHANGES HAVE BEEN MADE
AND HANNA IS EXPECTED TO CLEAR THE U.S. COASTLINE AROUND CAPE COD
MASSACHUSETTS BY 07/0900Z.

HANNA'S FAST FORWARD MOTION HAS LIKELY CONTRIBUTED TO SOME OF
INCREASE IN OBSERVED SURFACE WINDS OBTAINED FROM SHIPS AND BUOYS
SOUTH OF LONG ISLAND. TWO UNCONFIRMED SHIP REPORTS OF 64 KT AND 60
KT HAVE BEEN RECEIVED DURING THE PAST COUPLE OF HOURS...ONE OF
WHICH OCCURRED IN A RAIN BAND. HOWEVER...THESE COULD HAVE BEEN
ISOLATED GUSTS AND THE RAIN BANDS HAVE SINCE DISSIPATED.
THEREFORE...THE INITIAL INTENSITY WILL BE 50 KT FOR THIS ADVISORY
BASED ON EARLIER DOPPLER VELOCITY VALUES OF 70 KT AT 5000 TO 7000
FT THAT COVERED A SIGNIFICANT PORTION OF THE SOUTHEASTERN QUADRANT
OF HANNA IN SEVERAL RAIN BANDS. LITTLE CHANGE IN STRENGTH IS
EXPECTED THROUGHOUT THE FORECAST PERIOD...AND HANNA COULD EASILY BE
AN EXTRATROPICAL STORM WITH 50-KT SUSTAINED WINDS AT ANY OF THE
FORECAST TIMES.
  
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      07/0300Z 40.5N  73.4W    50 KT...BECOMING EXTRATROPICAL
 12HR VT     07/1200Z 43.0N  68.8W    50 KT...EXTRATROPICAL
 24HR VT     08/0000Z 46.4N  61.1W    45 KT...EXTRATROPICAL
 36HR VT     08/1200Z 48.8N  53.2W    45 KT...EXTRATROPICAL
 48HR VT     09/0000Z 50.0N  45.0W    45 KT...EXTRATROPICAL
 72HR VT     10/0000Z 52.5N  28.3W    45 KT...EXTRATROPICAL
 96HR VT     11/0000Z 56.5N  15.5W    45 KT...EXTRATROPICAL
120HR VT     12/0000Z 61.5N  11.5W    45 KT...EXTRATROPICAL
 
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FORECASTER STEWART
 
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