Hurricane ISABEL

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HURRICANE ISABEL DISCUSSION NUMBER   6
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
11 AM EDT SUN SEP 07 2003
 
SATELLITE IMAGERY THIS MORNING INDICATES THAT ISABEL HAS DEVELOPED A
VERY LARGE RAGGED EYE. SATELLITE INTENSITY ESTIMATES ARE 65 KT FROM
TAFB AND SAB...AND 77 KT FROM AFWA...SO THE INITIAL INTENSITY IS
SET AT 65 KT. THE UPPER-LEVEL OUTFLOW PATTERN IS NEARLY CIRCULAR
AND APPEARS TO BE UNRESTRICTED AND EXPANDING.
 
THE INITIAL MOTION IS 295/09...BASED ON ABOUT A 9 HOUR MOTION
BETWEEN SUCCESSIVE MICROWAVE POSITIONS. THE EYE FEATURE IS RAGGED
AND NOT REALLY A TRUE EMBEDDED EYE. CONVENTIONAL WATER VAPOR AND
SSMI VAPOR SATELLITE IMAGERY INDICATE DRY AIR HAS BEEN WRAPPING
INTO THE CENTER FROM THE SOUTHEAST THROUGH NORTHEAST...WHICH HAS
ACTUALLY ERODED THE CONVECTION ON THE NORTH SIDE. FOR THIS REASON
...THE INITIAL POSITION WAS PLACED NEAR THE SOUTHERN EDGE OF THE
'EYE' AND CLOSER TO THE DEEPEST CONVECTION. EVEN WITH THAT...THE
INITIAL POSITION IS STILL MORE THAN 40 NMI NORTH OF THE PREVIOUS
ADVISORY POSITION. THE GLOBAL MODELS ARE IN FAIRLY GOOD AGREEMENT
AND THERE IS GOOD CONVERGENCE ON A WEST-NORTHWESTWARD TRACK THROUGH
48-72 HOURS...WITH A MORE WESTWARD MOTION AFTER THAT. THIS IS
CONSISTENT WITH THE DEVELOPING SYNOPTIC PATTERN...WHICH INDICATES
THAT THE SUBTROPICAL RIDGE ALONG 32N LATITUDE SHOULD GRADUALLY
SHIFT WESTWARD AND PERHAPS EVEN CLOSE OFF A 500 MB HEIGHT CENTER A
COUPLE HUNDRED MILES SOUTHEAST OF BERMUDA. THE OFFICIAL TRACK IS
SIMILAR TO BUT TO THE RIGHT OF THE PREVIOUS TRACK...MAINLY DUE TO
THE MORE NORTHERLY INITIAL POSITION.

AT LEAST STEADY STRENGTHENING SHOULD OCCUR SINCE ISABEL NOW HAS AN
EYE FEATURE...IS OVER 82F WATER WITH WARMER SSTS AHEAD...AND HAS AN
IMPRESSIVE OUTFLOW PATTERN. BOTH THE SHIPS AND GFDL INTENSITY
MODELS BRING ISABEL UP TO 96 KT IN 42-60 HOURS...SO THIS TREND WAS
CLOSELY FOLLOWED. THE INTENSITY WAS LEVELED OFF AFTER 48 HOURS
SINCE ISABEL IS FORECAST TO BEGIN CROSSING A POSSIBLE COLD WAKE
LEFT BEHIND BY HURRICANE FABIAN LAST WEEK.
 
FORECASTER STEWART
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      07/1500Z 14.5N  37.7W    65 KT
 12HR VT     08/0000Z 15.1N  39.2W    75 KT
 24HR VT     08/1200Z 15.8N  41.3W    85 KT
 36HR VT     09/0000Z 16.6N  43.8W    95 KT
 48HR VT     09/1200Z 17.3N  46.3W   100 KT
 72HR VT     10/1200Z 18.5N  51.0W   100 KT
 96HR VT     11/1200Z 19.0N  55.5W   100 KT
120HR VT     12/1200Z 19.5N  60.0W   100 KT
 
 
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