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HURRICANE ISIDORE DISCUSSION NUMBER  17
NATIONAL WEATHER SERVICE MIAMI FL
5 AM EDT FRI SEP 20 2002
 
THE INITIAL MOTION ESTIMATE IS 305/7.  THE CENTER CAN BE SEEN ON THE
KEY WEST AND HAVANA RADARS AS WELL AS BEING TRACKED BY AIRCRAFT.
THE 00Z NWS GLOBAL FORECAST SYSTEM MODEL SHOWS A BIT OF MID LEVEL
RIDGE HOLDING TO THE NORTH OF ISIDORE FOR THE NEXT 72 HOURS.  FOR
THE FIRST 24 HOURS THE GLOBAL MODELS ARE IN GOOD AGREEMENT ABOUT A
CONTINUED SLOW MOSTLY NORTHWESTWARD.  THE AVIATION MODEL AND UKMET
SHOW A WEST TO WEST-SOUTHWESTWARD MOTION AFTER 48 HOURS WHILE THE
GFDL AND NOGAPS SHOW A MUCH SLOWER WESTWARD MOTION. AFTER THAT...THE
NEXT SHORT WAVE IN THE WESTERLIES IS FORECAST TO BE NORTH OF THE
GULF OF MEXICO IN ABOUT 72 HOURS AND WE WILL AGAIN STRUGGLE WITH
WHETHER OR NOT THE NEXT TROUGH WILL PICK UP ISIDORE.  IN ANY CASE
...ISIDORE WILL BE WITH US FOR QUITE SOME TIME.  THE OFFICIAL
FORECAST IS ADJUSTED SLIGHTLY TO THE LEFT OF THE PREVIOUS ADVISORY
AND WITH AN EVEN SLOWER FORWARD SPEED...BUT IS STILL TO THE RIGHT OF
ALMOST ALL THE GLOBAL GUIDANCE. ONLY THE CANADIAN MODEL IS TO THE
RIGHT OF THE OFFICIAL FORECAST TRACK.
 
THE LAST FIX FROM AN AIR FORCE PLANE NEAR 08Z REPORTED 967 MB
CENTRAL PRESSURE.AND A RECENT DROPSONDE INDICATED THAT SURFACE WINDS 
ARE NEAR 90 KNOTS NEAR THE 12 NMI DIAMETER EYEWALL.  AS SUGGESTED BY 
THE SHIPS STATISTICAL-DYNAMICAL MODEL...THE INTENSIFICATION PROCESS
COULD BE TEMPORARILY HALTED DURING THE NEXT 24 HOURS AS THE CORE OF
THE HURRICANE INTERACTS WITH WESTERN CUBA.  BUT INTENSIFICATION IS
EXPECTED TO RESUME BY 36 HOURS AS THE HURRICANE MOVES INTO THE
SOUTHEASTERN GULF OF MEXICO.  THERE ARE ONLY 3 OUT OF 5 REQUIRED
PARAMETERS MET FOR RAPID INTENSIFICATION COMPARED TO 4 OUT OF 5 SIX
HOURS AGO.  ALSO THE SHIPS DIAGNOSED INITIAL VERTICAL SHEAR IS UP TO
20 KNOTS FROM 14 KNOTS SIX HOURS AGO.
 
THE CENTER OF THE HURRICANE IS NEAR ITS POINT OF CLOSEST APPROACH TO
THE FLORIDA KEYS.  SO UNLESS THE WIND FIELD EXPANDS TOWARD FLORIDA
...THE WIND SPEEDS IN THE KEYS SHOULD REMAIN IN THE 25-KNOT RANGE
AND THE TROPICAL STORM WATCH WILL NOT BE UPGRADED TO A WARNING ON
THIS ADVISORY.
 
FORECASTER LAWRENCE
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     20/0900Z 21.3N  83.3W    90 KTS
12HR VT     20/1800Z 22.0N  84.1W   100 KTS
24HR VT     21/0600Z 22.7N  85.2W    95 KTS
36HR VT     21/1800Z 23.0N  86.0W   100 KTS
48HR VT     22/0600Z 23.2N  86.8W   105 KTS
72HR VT     23/0600Z 23.5N  87.5W   105 KTS
 
 
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