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TROPICAL STORM LISA DISCUSSION NUMBER   3
NATIONAL WEATHER SERVICE MIAMI FL
5 AM EDT TUE OCT 06 1998
 
TONIGHT COULD BE A TRIUMPH FOR NEW...OR RELATIVELY NEW...
TECHNOLOGY.  THE CENTER OF LISA WAS IMPOSSIBLE TO PINPOINT ON
CONVENTIONAL IR METEOSAT AND GOES8 IMAGERY...WITH SOME ANALYSES OF
THAT DATA GIVING A MISLEADING IMPRESSION THAT THE CENTER HAD
ACCELERATED TO ABOUT 14 KT ALONG 305 DEGREES.  ON THE OTHER
HAND...THE SPECIAL NIGHT IR CHANNEL ON THE GOES8 SPACECRAFT PROVIDES
A CLEARER VIEW. IT SHOWS THE SYSTEM TO HAVE SLOWED...TO 6 KT...AND
PERHAPS TO HAVE BEGUN ITS TURN TOWARD THE NORTH.  INITIAL HEADING IS
ESTIMATED TO BE 335 DEGREES OVER THE PAST FEW HOURS.
 
WATER VAPOR IMAGERY SHOWS AN UPPER-LEVEL LOW NEAR 23N 54W.  FLOW
AROUND THE SOUTH SIDE OF THE LOW CONTINUES TO SHEAR LISA.  THE
00Z AVN AND NOGAPS INDICATE THAT BOTH FEATURES ARE LIKELY TO BE
FORCED N TO NE BY THE DEEP LOW TO CUTOFF FROM THE WESTERLIES OVER
THE CENTRAL ATLANTIC.  TRACK GUIDANCE MODELS GENERALLY FOLLOW SUIT. 
BY 72 HOURS...THE AVN SHOWS LISA MERGING WITH THE ASSOCIATED
BAROCLINIC ZONE...BUT THERE IS SOME DOUBT AS TO WHETHER A TROPICAL
STORM AS LARGE AS THIS CAN BE SO QUICKLY AND COMPLETELY ABSORBED AT
SUCH A LOW LATITUDE...NEAR 30N.  THE NOGAPS SHOWS A HYBRID SYSTEM
EVENTUALLY DEVELOPING FROM THE INTERACTION.  EITHER WAY...
SIGNIFICANT NORTHWARD ACCELERATION IS LIKELY BY 72 HOURS.
 
ALTHOUGH DEEP CONVECTION HAS RECENTLY DIMINISHED IN COVERAGE...
INTENSIFICATION IS POSSIBLE IN THE SHORT TERM IF LISA BEGINS TO MOVE
TOWARD THE NE.  THE STORM COULD ALSO STRENGTHEN LATER ON IN RESPONSE
TO BAROCLINIC EFFECTS.  BOTH THE SHIPS AND GFDL SCHEMES INDICATE
STRENGTHENING.
 
RAPPAPORT
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     06/0900Z 17.2N  49.4W    40 KTS
12HR VT     06/1800Z 18.0N  49.4W    40 KTS
24HR VT     07/0600Z 19.6N  49.0W    40 KTS
36HR VT     07/1800Z 21.3N  47.8W    40 KTS
48HR VT     08/0600Z 23.9N  45.5W    45 KTS
72HR VT     09/0600Z 31.0N  41.0W    50 KTS
 
 
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