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HURRICANE ISIDORE DISCUSSION NUMBER  18
NATIONAL WEATHER SERVICE MIAMI FL
11 AM EDT FRI SEP 20 2002
 
THERE HAVE BEEN NO ADDITIONAL RECONNAISSANCE REPORTS THIS MORNING...
AND THERE HAVE BEEN NO SIGNIFICANT CHANGES SEEN ON SATELLITE
IMAGERY...SO THE INITIAL INTENSITY REMAINS AT 90 KT.  ISIDORE
REMAINS ON TRACK...300/7...TOWARD WESTERN CUBA.
 
TO ITS CREDIT...THE FORECAST FROM THE AVN YESTERDAY OF A STRONG
CUTOFF EAST OF FLORIDA SEEMS TO BE DEVELOPING ACCORDING TO ITS
PLAN...AND THE GUIDANCE ENVELOPE KEEPS SLIDING WESTWARD...INCREASING
THE THREAT TO THE YUCATAN AND DELAYING ANY THREAT TO THE UNITED
STATES GULF COAST.  THE SMALL UPPER-LEVEL LOW CURRENTLY WEST OF
ISIDORE IS SLIDING EAST IN ADVANCE OF THE FIRST TROUGH...BUT I DO
NOT BELIEVE THIS FEATURE IS DEEP ENOUGH TO PLAY A MAJOR ROLE IN THE
TRACK OF ISIDORE.  THERE SHOULD BE ENOUGH RIDGING IN THE NORTHERN
GULF TO KEEP ISIDORE BOTTLED UP AT LEAST UNTIL THE NEXT MID-LEVEL
SHORT WAVE MOVES INTO THE GULF IN ABOUT 72 HOURS.  WHERE ISIDORE
ACTUALLY TURNS OUT TO BE IN 72 HOURS WILL BE KEY IN DETERMINING
WHETHER IT GETS PICKED UP BY THE SECOND TROUGH OR NOT.  SHOULD THE
AVN BE RIGHT IN TAKING ISIDORE SOUTHWESTWARD OVER THE YUCATAN THEN
THE CYCLONE WILL LIKELY BE LEFT BEHIND...AGAIN.  HOWEVER...THERE
REMAINS CONSIDERABLE GUIDANCE...IN THE FORM OF THE GFDL...NOGAPS...
AND CANADIAN...THAT SUGGESTS THAT ISIDORE WILL BE FAR ENOUGH NORTH
TO BE PICKED UP AND BEGIN A NORTHWARD MOTION IN THE THREE TO FIVE
DAY TIME FRAME.  BUT IT IS STILL TOO CLOSE TO CALL.

THERE ARE INDICATIONS IN THE RADAR IMAGERY AND FLIGHT-LEVEL DATA 
THAT ISIDORE HAS A CONCENTRIC EYEWALL STRUCTURE.  GIVEN THIS...THE 
NEARBY LANDMASS...AND AN EXPECTED SQUEEZING OF THE UPPER-LEVEL 
OUTFLOW BY THE NEIGHBORING UPPER LOWS...I DO NOT EXPECT ANY MORE 
SIGNIFICANT STRENGTHENING OVER THE NEXT DAY OR SO.  AFTER 
THAT...THERE WILL BE AN OPPORTUNITY FOR ISIDORE TO BECOME A MAJOR 
HURRICANE.

FORECASTER FRANKLIN
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     20/1500Z 21.7N  83.9W    90 KTS
12HR VT     21/0000Z 22.1N  84.7W    90 KTS
24HR VT     21/1200Z 22.5N  85.5W    95 KTS
36HR VT     22/0000Z 22.8N  86.4W   100 KTS
48HR VT     22/1200Z 23.0N  87.5W   105 KTS
72HR VT     23/1200Z 23.0N  88.5W   105 KTS
 
 
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