Hurricane ISABEL

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HURRICANE ISABEL DISCUSSION NUMBER  22
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
11 AM EDT THU SEP 11 2003
 
ISABEL IS MORE SYMMETRICAL-LOOKING THAN IT WAS YESTERDAY...AND IT
HAS A TEXTBOOK APPEARANCE ON VISIBLE AND INFRARED SATELLITE IMAGES.
THE WELL-DEFINED 25 N MI DIAMETER EYE IS EMBEDDED IN VERY DEEP
CONVECTION.  DVORAK T-NUMBERS AVERAGE ABOUT 6.7 GIVING A CURRENT
INTENSITY ESTIMATE OF 130 KT.  THERE ARE NO OBVIOUS IMPEDIMENTS IN
THE ENVIRONMENT...SO CHANGES IN STRENGTH ARE LIKELY TO BE DICTATED
PRIMARILY BY INNER-CORE PROCESSES.  ISABEL SHOULD REMAIN A MAJOR
HURRICANE THROUGH THE FORECAST PERIOD.
 
THE HURRICANE IS MOVING WEST NEAR 8 KT AS IT REMAINS EMBEDDED IN
DEEP LAYER EASTERLIES TO THE SOUTH OF A HIGH PRESSURE SYSTEM.
GLOBAL AND GFDL MODEL GUIDANCE INDICATE A GRADUAL TURN TOWARD THE
WEST-NORTHWEST OVER THE NEXT FEW DAYS AS ISABEL NEARS THE WESTERN
SIDE OF THE HIGH.  THIS IS ALSO SHOWN IN THE OFFICIAL TRACK
FORECAST...WHICH IS QUITE CLOSE TO THE PREVIOUS ONE.  THE NHC TRACK
IS ALSO FAIRLY CLOSE TO THE GUNA CONSENSUS AND TO THE FSU
SUPERENSEMBLE TRACK.  THE LATEST GFDL RUN IS A LITTLE NORTHEAST OF
THE OFFICIAL TRACK...AND THAT MODEL HAS BEEN TRENDING MORE AND MORE
TO THE RIGHT IN THE LAST FEW RUNS.
 
LATE IN THE FORECAST PERIOD...THE TWO MOST IMPORTANT PLAYERS IN THE
STEERING OF ISABEL APPEAR TO BE THE RIDGE NEAR THE U.S. EAST COAST
AND A MID-LATITUDE TROUGH OVER THE EAST-CENTRAL UNITED STATES.
THERE IS SOME DIFFERENCE IN THE WAY THE DYNAMICAL GUIDANCE HANDLES
THESE FEATURES.  SOME OF THE MODELS...SUCH AS THE GFS...NOW SHOW
THE TROUGH AS THE MORE DOMINANT SYSTEM.  IF THIS TURNS OUT TO BE
THE CASE...THEN THE HURRICANE COULD TURN MORE NORTHWARD THAN SHOWN
HERE.
 
FORECASTER PASCH
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      11/1500Z 21.4N  54.5W   130 KT
 12HR VT     12/0000Z 21.5N  56.0W   130 KT
 24HR VT     12/1200Z 21.8N  58.0W   130 KT
 36HR VT     13/0000Z 22.2N  60.0W   125 KT
 48HR VT     13/1200Z 22.8N  61.9W   120 KT
 72HR VT     14/1200Z 24.0N  65.5W   115 KT
 96HR VT     15/1200Z 25.0N  69.0W   115 KT
120HR VT     16/1200Z 26.5N  72.0W   115 KT
 
 
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