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TROPICAL DEPRESSION TEN DISCUSSION NUMBER   4
NATIONAL WEATHER SERVICE MIAMI FL
11 AM EDT SUN SEP 15 2002

HIGH-RESOLUTION VISIBLE SATELLITE IMAGES AND SURFACE OBSERVATIONS 
SUGGEST THAT THE SYSTEM HAS NOT YET STRENGTHENED...AND THE LOW-LEVEL 
CENTER IS NOT WELL DEFINED.  AN AIR FORCE RESERVE UNIT AIRCRAFT 
SHOULD BE IN THE SYSTEM SHORTLY TO GIVE A BETTER MEASUREMENT OF ITS 
INTENSITY.  THE KEY TO THE FUTURE INTENSITY OF THE TROPICAL CYCLONE 
IS THE EVOLUTION OF THE UPPER-LEVEL TROUGH CURRENTLY OVER THE 
WEST-CENTRAL CARIBBEAN.  THE TROUGH IS MOVING WESTWARD...AND GLOBAL 
MODELS SUGGEST THAT IT WILL CONTINUE TO MOVE WESTWARD AND BECOME 
MORE OF A CUTOFF LOW OR INVERTED TROUGH.  IF THIS OCCURS...IT WOULD 
PROVIDE A FAVORABLE UPPER-LEVEL ENVIRONMENT FOR STRENGTHENING OVER 
THE NEXT FEW DAYS.  IN THE LATTER PART OF THE FORECAST PERIOD...HIGH 
UPPER OCEANIC HEAT CONTENT MAY ALSO BE A CONTRIBUTING FACTOR FOR 
INTENSIFICATION AS SUGGESTED BY THE EXPERIMENTAL SHIPS MODEL.  THUS 
EVEN THOUGH THE CURRENT STATE OF THE SYSTEM IS NOT ALL THAT 
IMPRESSIVE...THE OFFICIAL FORECAST CALLS FOR STRENGTHENING AS IN THE 
PREVIOUS ADVISORY.

CENTER FIXES HAVE A LOT OF SCATTER BUT MY BEST ESTIMATE OF INITIAL 
MOTION IS 285/19 AS A STRONG MID-LEVEL RIDGE TO THE NORTH CONTINUES 
TO DOMINATE THE STEERING.  MUCH OF THE TRACK GUIDANCE HAS CONTINUED 
TO SHIFT WESTWARD IN COMPARISON TO THE PREVIOUS ADVISORY PACKAGES. 
THE RIDGE TO THE NORTH OF THE CYCLONE IS FORECAST TO GRADUALLY 
WEAKEN AND SHIFT WESTWARD LATE IN THE PERIOD.  THUS THE OFFICIAL 
FORECAST SHOWS SOME SLOWING OF THE FORWARD SPEED AN A GRADUAL TURN 
TO THE NORTHWEST.  ALTHOUGH A LOT OF THE MODELS HAVE SHIFTED 
WESTWARD...THE OFFICIAL FORECAST TRACK IS ONLY SLIGHTLY WEST OF THE 
PREVIOUS ONE OUT OF RESPECT FOR THE NCEP AND U.K. MET MODEL 
FORECASTS WHICH FAVOR A TRACK TO THE NORTH AND EAST OF THE REST OF 
THE GUIDANCE.

FORECASTER PASCH
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     15/1500Z 11.5N  67.2W    25 KTS
12HR VT     16/0000Z 12.6N  70.2W    30 KTS
24HR VT     16/1200Z 14.5N  73.7W    40 KTS
36HR VT     17/0000Z 16.2N  76.5W    50 KTS
48HR VT     17/1200Z 17.5N  78.5W    60 KTS
72HR VT     18/1200Z 19.5N  80.5W    75 KTS
 
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