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Hurricane ISABEL


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HURRICANE ISABEL DISCUSSION NUMBER  25
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
5 AM EDT FRI SEP 12 2003
 
THERE ARE NO NEW CHANGES TO REPORT OR THAT CAN BE ADDED TO THE
STRUCTURE AND INTENSITY OF ISABEL AFTER THE PREVIOUS DISCUSSION.
BASED ON THE OUSTANDING CLOUD PATTERN...SATELLITE INTENSITY
ESTIMATES STILL SUPPORT 140 KNOTS. REGARDLESS OF HOW THE CORE
STRUCTURE EVOLVES IN THE NEAR TERM...ISABEL IS EXPECTED TO REMAIN A
MAJOR HURRICANE THROUGHOUT THE FORECAST PERIOD.
 
HERE COMES A LITTLE DISCUSSION ABOUT THE FOUR MAIN MODELS. THE GFDL
WHICH HAS BEEN PERFORMING QUITE WELL...TURNS THE HURRICANE MORE TO
THE NORTHWEST AND NORTH-NORTHWEST...AND DEPENDING UPON THE RUN YOU
PICK...THE TURN OCCURS FARTHER TO THE WEST OR FARTHER TO THE EAST.
ON THE OTHER HAND...THE UK MODEL WHICH HAS HAS BEEN MORE CONSISTENT
...MOVES THE HURRICANE FASTER AND BRING ISABEL DANGEROUSLY CLOSE TO
THE U.S. COAST IN 5 DAYS. THE GFS WHICH HAS BEEN CHANGING ITS TUNE
FROM RUN TO RUN...IS MUCH SLOWER AND IN 5 DAYS PLACES THE HURRICANE
ABOUT 450 N MI FROM THE U.S COAST. THE GFS EVENTUALLY BRINGS THE
CENTER NEAR THE COAST OF NORTH CAROLINA IN SEVERAL MORE DAYS.
FINALLY...THE NOGAPS IS VERY SIMILAR TO THE GFS UP TO 5 DAYS.
 
NOTE: THEY ALL HAVE IN COMMON THE DEVELOPMENT AND THE WESTWARD
EXPANSION OF A STRONG RIDGE TO THE NORTH OF THE HURRICANE BEYOND 5
DAYS. IF THIS PATTERN EVOLVES...THE HURRICANE COULD POSE A
SIGNIFICANT THREAT TO THE U.S. EAST COAST.
 
HAVING SAID ALL THAT...HERE COMES THE OFFICIAL FORECAST. ISABEL HAS
BEEN MOVING TOWARD THE WEST OR 270 DEGREES AT 8 KNOTS AROUND A
DEEP-LAYER SUBTROPICAL HIGH.  THIS PATTERN WOULD FAVOR A WEST TO
WEST-NORTHWEST TRACK THROUGH 5 DAYS WITH NO SIGNIFICANT CHANGE IN
FORWARD SPEED.  MOST IMPORTANTLY...DUE TO THE LARGE VARIATION IN
MODELS FROM RUN TO RUN...IT IS TOO EARLY TO SPECULATE WHAT PORTIONS
OF THE U.S. EAST COAST MIGHT BE AFFECTED BY ISABEL.
 
FORECASTER AVILA
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      12/0900Z 21.7N  57.0W   140 KT
 12HR VT     12/1800Z 22.0N  58.4W   130 KT
 24HR VT     13/0600Z 22.5N  60.5W   135 KT
 36HR VT     13/1800Z 23.0N  62.5W   130 KT
 48HR VT     14/0600Z 23.5N  64.5W   125 KT
 72HR VT     15/0600Z 25.0N  69.0W   115 KT
 96HR VT     16/0600Z 26.0N  71.5W   115 KT
120HR VT     17/0600Z 27.5N  74.0W   110 KT
 
 
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