ISABEL #21 - DISCUSSION

[AussieMark]

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WTNT43 KNHC 110900
TCDAT3
HURRICANE ISABEL DISCUSSION NUMBER 21
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
5 AM EDT THU SEP 11 2003

...CORRECTION FOR EASTERLY FLOW INSTEAD OF WESTERLY FLOW

THE CLOUD PATTERN IS EXCELLENT WITH A DISTINCT EYE SURROUNDED BY
VERY DEEP CONVECTION. WATER VAPOR IMAGES SHOW THAT ISABEL CONTINUES
TO HAVE TWO WELL-ESTABLISHED AND IMPRESSIVE OUTFLOW CHANNELS.
INITIAL INTENSITY REMAINS AT 125 KNOTS AND BECAUSE THE SHEAR IS LOW
AND THE OCEAN IS WARM...ISABEL WILL LIKELY REMAIN A MAJOR HURRICANE
THROUGH 5 DAYS.

ISABEL IS MOVING WESTWARD ABOUT 9 KNOTS EMBEDDED WITHIN A DEEP LAYER
EASTERLY FLOW SOUTH OF A HIGH PRESSURE RIDGE. THIS RIDGE IS
FORECAST TO PERSIST FORCING ISABEL TO MOVE ON A GENERAL WESTWARD
TRACK. BECAUSE THE RIDGE SHOULD BEGIN TO TEMPORARELY
WEAKEN...ISABEL COULD TURN MORE TO THE WEST-NORTHWEST IN ABOUT 24
TO 36 HOURS. GLOBAL MODELS ARE CLUSTERED AND THEY ALL SUGGEST A
WEST-NORTHWEST TURN...BRINGING THE CORE OF ISABEL PARALLEL AND JUST
TO THE NORTH OF THE BAHAMAS. IN FACT THE GFS...NO LONGER BRINGS
ISABEL STRAIGHT WESTWARD AS IN PREVIOUS RUNS AND THE GFDL...WHICH
HAS BEEN PERFORMING QUITE WELL SO FAR...HAS SHIFTED THE TRACK
SLIGHTLY NORTHWARD.

NOTE: ALL MODELS RE-DEVELOP A RIDGE OVER THE WESTERN ATLANTIC JUST
OFF THE U.S. EAST COAST IN ABOUT 5 DAYS. THE STRENGTH AND LOCATION
OF THIS RIDGE WILL BE CRITICAL IN DETERMINING HOW CLOSE ISABEL WILL
GET TO THE UNITED STATES EAST COAST.

FORECASTER AVILA

FORECAST POSITIONS AND MAX WINDS

INITIAL 11/0900Z 21.3N 53.7W 125 KT
12HR VT 11/1800Z 21.4N 55.1W 125 KT
24HR VT 12/0600Z 21.7N 57.0W 125 KT
36HR VT 12/1800Z 22.0N 59.0W 120 KT
48HR VT 13/0600Z 22.5N 61.0W 120 KT
72HR VT 14/0600Z 24.0N 65.0W 115 KT
96HR VT 15/0600Z 25.0N 69.0W 115 KT
120HR VT 16/0600Z 26.0N 72.0W 115 KT