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TROPICAL STORM IVAN DISCUSSION NUMBER   5
NATIONAL WEATHER SERVICE MIAMI FL
11 AM EDT MON SEP 21 1998
 
A MODERATE SHEARING PATTERN PERSISTS WITH THE CIRCULATION CENTER
ESTIMATED TO BE UNDER THE WESTERN PART OF THE SMALL CENTRAL DENSE
OVERCAST.  THE INITIAL HEADING IS ADJUSTED TO 310 DEGREES AT 12 KT.
 
AN ELONGATED TROUGH EXTENDING SOUTHWARD FROM 30N TO SOUTHWEST OF
IVAN IS INDUCING THE CURRENT SHEAR.  IF THE DEPTH OF THIS FEATURE IS
GREAT ENOUGH IT WILL TURN THE STORM MORE TOWARD THE NORTH IN TIME
WITH THE SHEAR POTENTIALLY DECREASING.  ALTERNATELY...IF IT IS
RATHER SHALLOW...THEN IVAN COULD CONTINUE TO MOVE TOWARD THE WEST-
NORTHWEST BUT BECOME EVEN MORE SHEARED.  MOST OF THE TRACK GUIDANCE
AND THE NHC FORECAST IS BETWEEN THESE EXTREMES...SUGGESTING A NW
MOTION AND LITTLE CHANGE IN INTENSITY.
 
RAPPAPORT
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     21/1500Z 18.8N  36.2W    35 KTS
12HR VT     22/0000Z 19.9N  37.6W    35 KTS
24HR VT     22/1200Z 21.5N  39.1W    35 KTS
36HR VT     23/0000Z 22.9N  40.8W    35 KTS
48HR VT     23/1200Z 24.5N  42.6W    35 KTS
72HR VT     24/1200Z 27.5N  45.5W    40 KTS
 
 
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