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TROPICAL STORM JEANNE DISCUSSION NUMBER  34
NATIONAL WEATHER SERVICE MIAMI FL
11 PM EDT TUE SEP 29 1998
 
THE INITIAL MOTION ESTIMATE IS 060/09.
 
MODEL GUIDANCE...
THE AVIATION MODEL AND NOGAPS SHOW A MOSTLY NORTHEASTWARD MOTION
THROUGH 72 HOURS WHILE THE GFDL AND LBAR SHOW A TURN TOWARD THE
EAST.  THE UKMET SHOWS A TURN TOWARD THE NORTH APPARENTLY IN
RESPONSE TO A FRONTAL LOW TO THE WEST OF THE STORM OVERTAKING IT AND
ADVECTING IT NORTHWARD.  THE BAM MODELS SUGGEST THAT A STRONGER
SYSTEM WITH MORE VERTICAL EXTENT WILL HAVE MORE OF AN EASTWARD
COMPONENT THAN A WEAKER SHEARED SYSTEM.
 
THE OFFICIAL FORECAST TRACK IS A CONSENSUS OF THE MODELS AND IS A
LITTLE LEFT OF THE PREVIOUS NHC FORECAST...BASED ON A CONTINUATION
OF THE SHEARING WHICH IS OCCURRING.
 
THIS SHEARING IS CAUSING THE LOW LEVEL CENTER TO BE EXPOSED TO THE
WEST OF THE CONVECTION AND IS THE BASIS FOR DECREASING THE CURRENT
WIND SPEED TO 50 KNOTS AND FOR FORECASTING CONTINUED WEAKENING.
COOLER SSTS ALSO ARE PART OF THE REASONING FOR WEAKENING.  THE
OVERTAKING FRONTAL LOW MAY ALSO BE THE MECHANISM FOR CAUSING JEANNE
TO BECOME EXTRATROPICAL...PERHAPS IN 24 TO 36 HOURS...IF NOT SOONER.
 
LAWRENCE
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     30/0300Z 37.2N  33.2W    50 KTS
12HR VT     30/1200Z 37.8N  31.8W    45 KTS
24HR VT     01/0000Z 38.6N  30.0W    40 KTS
36HR VT     01/1200Z 39.5N  27.5W    35 KTS...EXTRATROPICAL
48HR VT     02/0000Z 40.5N  25.0W    30 KTS...EXTRATROPICAL
72HR VT     03/0000Z 41.0N  19.0W    30 KTS...EXTRATROPICAL
 
 
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