Hurricane IVAN

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HURRICANE IVAN DISCUSSION NUMBER  17
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
11 AM EDT MON SEP 06 2004

A SMALL EYE IS EVIDENT ON THE VISIBLE IMAGERY.  THERE IS A SMALL CDO
AND SOMEWHAT RAGGED-LOOKING BANDING FEATURES.  ESTIMATES OF THE
DATA T-NUMBER RANGE FROM 4.5 TO 5.5 SO THERE IS CONSIDERABLE
UNCERTAINTY IN THE CURRENT INTENSITY.  SINCE THE HURRICANE APPEARED
TO BE SO INTENSE LAST NIGHT...WE ARE HOLDING THE WIND SPEED AT 110
KT IN GENERAL AGREEMENT WITH DVORAK RULES.  AN AIR FORCE HURRICANE
HUNTER AIRCRAFT IS SCHEDULED TO INVESTIGATE IVAN AROUND 18Z AND
THIS SHOULD PROVIDE A MUCH BETTER ESTIMATE OF THE STRENGTH OF THIS
HURRICANE.  THE SHIPS GUIDANCE SHOWS SOME SLIGHT WESTERLY SHEAR IN
THE ENVIRONMENT OF IVAN...PROBABLY DUE TO A WEAK UPPER-LEVEL LOW
OVER THE EAST-CENTRAL CARIBBEAN.  HOWEVER THAT MODEL ALSO SHOWS
INTENSIFICATION OF IVAN.  SINCE THE SHEAR IS NOT EXPECTED TO BECOME
VERY HIGH...THE OFFICIAL FORECAST ALSO INDICATES INTENSIFICATION. 
THE INTENSITY PREDICTION AT DAYS 4 AND 5 HAS THE ADDED UNCERTAINTY
OF HOW IVAN WILL INTERACT WITH THE LAND MASSES OF HISPANIOLA AND
EASTERN CUBA.

INITIAL MOTION ESTIMATE IS SLIGHTLY NORTH OF DUE WEST...280/19. 
THERE HAS BEEN LITTLE CHANGE TO THE TRACK FORECAST PHILOSPHY. IVAN
IS EMBEDDED IN A WELL-DEFINED EASTERLY STEERING CURRENT AND SHOULD
REMAIN SO OVER THE NEXT FEW DAYS.  LATE IN THE FORECAST
PERIOD...THE MOTION OF THE HURRICANE WILL DEPEND ON THE STRENGTH
AND POSITIONS OF A RIDGE OVER THE EXTREME SOUTHWEST ATLANTIC AND A
TROUGH OVER THE EAST-CENTRAL UNITED STATES.  IT IS STILL TO EARLY
TO CONFIDENTLY PREDICT WHETHER IVAN WILL BE SOUTH OF...OVER...OR
NORTH OF CUBA AROUND 5 DAYS.  THE CURRENT NHC TRACK FORECAST IS
VERY CLOSE TO THE LATEST DYNAMICAL MODEL CONSENSUS.  IT SHOULD BE
NOTED THAT THE LATEST FSU SUPERENSEMBLE RUN IS TO THE SOUTH OF THE
OFFICIAL TRACK BEYOND 3 DAYS.

HURRICANE WARNINGS HAVE BEEN ISSUED FOR SEVERAL OF THE WINDWARD
ISLANDS.
 
FORECASTER PASCH
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      06/1500Z 11.2N  53.4W   110 KT
 12HR VT     07/0000Z 11.8N  56.1W   115 KT
 24HR VT     07/1200Z 12.7N  59.5W   115 KT
 36HR VT     08/0000Z 13.7N  62.7W   120 KT
 48HR VT     08/1200Z 15.0N  65.5W   125 KT
 72HR VT     09/1200Z 17.5N  71.0W   125 KT
 96HR VT     10/1200Z 20.5N  75.0W    75 KT...INLAND
120HR VT     11/1200Z 23.5N  78.5W    90 KT...OVER WATER
 
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