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TROPICAL STORM LISA DISCUSSION NUMBER   4
NATIONAL WEATHER SERVICE MIAMI FL
11 AM EDT TUE OCT 06 1998
 
LISA HAS BEGUN TO MOVE TOWARD THE NORTHEAST ABOUT 10 KNOTS AHEAD OF
A MAJOR MID-TROPOSPHERIC TROUGH OVER THE MIDDLE ATLANTIC AND AROUND
A LARGE UPPER-LOW CENTERED NEAR 21N 55W.  THIS PATTERN IS PRODUCING
MID TO UPPER LEVEL WESTERLIES BASICALLY OVER MOST OF THE WESTERN
ATLANTIC AND THE CARIBBEAN AS CLEARLY SEEN ON WV IMAGES.  IN
RESPONSE TO THAT PATTERN...LISA HAS RECURVED AND IS FORECAST TO
CONTINUE ON THIS GENERAL NORTHEASTWARD TRACK WITH A GRADUAL INCREASE
IN FORWARD SPEED OVER OPEN WATER THROUGH 72 HOURS.  THIS IS
CONSISTENT WITH MOST OF THE TRACK MODELS.
 
SINCE LISA IS MOVING NORTHEASTWARD...ON THE SAME DIRECTION OF THE
UPPER FLOW...THE RELATIVE SHEAR HAS DECREASED AND CONSEQUENTLY THE
LOW-LEVEL CENTER IS CURRENTLY BACK UNDER THE CONVECTION. THIS
SUGGESTS THAT LISA COULD BE A LITTLE STRONGER THAN INDICATED BUT WE
WOULD RATHER WAIT TO SEE IF THE CENTER REMAINS UNDER THE OVERCAST TO
ADJUST THE INITIAL INTENSITY.  NEVERTHELESS...ONLY A SMALL
STRENGTHENING IS FORECAST.
 
AVILA
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     06/1500Z 18.0N  48.3W    40 KTS
12HR VT     07/0000Z 19.0N  47.3W    45 KTS
24HR VT     07/1200Z 21.0N  46.0W    45 KTS
36HR VT     08/0000Z 23.5N  44.0W    45 KTS
48HR VT     08/1200Z 26.5N  41.0W    45 KTS
72HR VT     09/1200Z 33.0N  37.0W    45 KTS
 
 
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