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TROPICAL STORM ISIDORE DISCUSSION NUMBER  14
NATIONAL WEATHER SERVICE MIAMI FL
11 AM EDT THU SEP 19 2002
 
A DROPSONDE JUST BEFORE 12Z REPORTED MEAN WINDS IN ITS LOWEST LAYERS 
OF 75 KT.  ADJUSTMENT OF THIS OB TO THE SURFACE GIVE 59 KT...AND IS 
THE BASIS FOR AN INCREASE IN THE ADVISORY WINDS TO 60 KT.  A 
MICROWAVE OVERPASS AT 12Z SHOWED A PRETTY SOLID EYEWALL.  THE NEXT 
RECONNAISSANCE AIRCRAFT WILL BE IN THE SYSTEM AT 18Z...AND THEY WILL 
PROBABLY FIND A HURRICANE.  

THE CYCLONE HAS NOT MOVED MUCH OVER THE PAST FEW HOURS WHILE THIS 
EYEWALL HAS BEEN FORMING...BUT AN AVERAGE MOTION OVER THE LAST 6 TO 
12 HOURS IS 290/7.  THE SHORT-TERM MODEL GUIDANCE REMAINS IN GOOD 
AGREEMENT ON A WNW-NW TRACK TOWARDS WESTERN CUBA.  NEAR THE END OF 
THE FORECAST PERIOD ISIDORE SHOULD STALL AS THE TROUGH CURRENTLY 
OVER THE CENTRAL U.S. BYPASSES THE CYCLONE.  THIS LEAVES ISIDORE IN 
A VERY WEAK STEERING ENVIRONMENT IN THE SOUTHEASTERN GULF OF MEXICO. 
THE SOUTHEASTERN GULF SOUTH OF 25N HAS AMPLE WARM WATER TO 
SIGNIFICANT DEPTHS...SO A STALL THERE WOULD NOT HINDER DEVELOPMENT.  
AN ADDITIONAL CONCERN IS THE ALREADY EXPANDING WIND FIELD TO THE 
EAST OF ISIDORE...AND SO THERE IS A RISK OF TROPICAL STORM FORCE 
WINDS IN THE LOWER KEYS EVEN IF THE CENTER REMAINS ON TRACK.  A 
WATCH OR WARNING MAY BE REQUIRED THERE LATER TODAY.

DUST OFF THE CHAOS BUTTERFLIES OF MIT PROFESSOR ED LORENZ.  BEYOND 
THREE DAYS...THERE IS COMPLETE DIVERGENCE OF THE MODEL GUIDANCE...AS 
A SERIES OF SHORT WAVES IN THE WESTERLIES SLIDE ALONG SOUTH OF THE 
MEAN TROUGH THAT SHOULD LINGER OVER THE GREAT LAKES.  EACH MODEL HAS 
ITS OWN PERSONAL INTERACTION OF ISIDORE WITH A SHORT WAVE OF ITS 
CHOOSING...LEADING TO 5 DAY FORECAST POSITIONS RANGING FROM THE 
YUCATAN TO JACKSONVILLE.  IT IS SIMPLY NOT POSSIBLE YET TO BE 
CONFIDENT IN WHICH EVOLUTION WILL TURN OUT TO BE CORRECT...AS VERY 
SUBTLE CHANGES IN THE POSITION OF ISIDORE THREE DAYS FROM NOW COULD 
TURN OUT TO BE VERY IMPORTANT. 
 
FORECASTER FRANKLIN
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     19/1500Z 20.0N  81.2W    60 KTS
12HR VT     20/0000Z 20.9N  82.2W    70 KTS
24HR VT     20/1200Z 22.0N  83.6W    75 KTS
36HR VT     21/0000Z 23.0N  84.5W    75 KTS
48HR VT     21/1200Z 23.5N  85.0W    85 KTS
72HR VT     22/1200Z 24.5N  86.0W    95 KTS
 
 
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