[Tropical] Tropical Cyclone Discussion

[Nashville EMWIN]

WTNT44 KNHC 110844
TCDAT4
HURRICANE IVAN DISCUSSION NUMBER  36
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
5 AM EDT SAT SEP 11 2004

A U.S. AIR FORCE RESERVE UNIT AIRCRAFT IS CURRENTLY FLYING IN THE
HURRICANE.  THE CENTRAL PRESSUURE IS 924 MB AND FLIGHT LEVEL WINDS
SUPPORT 125 KT SURFACE WINDS.  HOWEVER THE HURRICANE IS UNDERGOING
AN EYEWALL REPLACEMENT CYCLE AND MAY SOON BE INTENSIFYING AND THE
INITIAL WIND SPEED IS SET AT 130 KT.  WITH LIGHT VERTICAL SHEAR AND
WARM SSTS...CONDITIONS APPEAR FAVORABLE FOR STRENGHENING FOR THE
NEXT DAY OR TWO AS IVAN THREATENS THE CAYMAN ISLANDS AND THEN CUBA.

THE EYE TOOK A WESTWARD WOBBLE OVERNIGHT AND REMAINED FAR ENOUGH
SOUTH OF JAMAICA SO THAT THE STRONGEST WINDS ARE BELIEVED TO HAVE
REMAINED OFFSHORE.  NEVERTHELESS...JAMAICA EXPERIENCED HURRICANE
FORCE WINDS AND IS STILL DOING SO.

THE GUIDANCE CONTINUES TO SHOW THE SAME FORECAST SCENARIO OF A TURN
TOWARD THE NORTHWEST AND THEN NORTH THROUGH A WEAKNESS IN THE
SUBTROPICAL RIDGE.  THE RUNS OF THE FOUR GLOBAL TRACK GUIDANCE
MODELS...GFS...GFDL...UKMET...NOGAPS...ALL SHIFTED THEIR TRACK A
LITTLE TO THE LEFT.  SOME OR ALL OF THE SHIFT COULD BE DUE TO THE
SHORT TERM WESTWARD WOBBLE.  THE OFFICIAL TRACK FORECAST IS
ADJUSTED A LITTLE LEFT OF THE PREVIOUS ADVISORY BUT IS STILL TO THE
RIGHT OR EAST OF ALL THE MODELS THROUGH 48 HOURS AND THEN IS CLOSER
TO A CONSENSUS OF THE MODELS AFTER 48 HOURS.  THE GUIDANCE MODELS
INDICATE A DECREASE IN FORWARD SPEED FOR THE NEXT DAY OR SO AND SO
DOES THE OFFICIAL FORECAST.

FORECASTER LAWRENCE

FORECAST POSITIONS AND MAX WINDS

INITIAL      11/0900Z 17.5N  78.0W   130 KT
 12HR VT     11/1800Z 18.3N  79.0W   135 KT
 24HR VT     12/0600Z 19.3N  80.1W   140 KT
 36HR VT     12/1800Z 20.6N  81.4W   140 KT
 48HR VT     13/0600Z 22.0N  82.5W   140 KT
 72HR VT     14/0600Z 25.9N  83.8W   115 KT
 96HR VT     15/0600Z 30.5N  84.0W    90 KT...INLAND
120HR VT     16/0600Z 36.0N  83.0W    30 KT...INLAND


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