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HURRICANE LENNY DISCUSSION NUMBER  24
NATIONAL WEATHER SERVICE MIAMI FL
4 AM EST FRI NOV 19 1999
 
DATA FROM WSR-88D DOPPLER RADAR IN SAN JUAN...AN AIR FORCE RESERVE
HURRICANE HUNTER...AND SURFACE OBSERVATIONS IN ST. MAARTEN INDICATE
THE EYE OF LENNY DRIFTED ERRATICALLY SOUTHEAST EARLIER TONIGHT. IT
NOW APPEARS TO BE STATIONARY. ST. MAARTEN IS VERY NEAR THE WESTERN
EYEWALL...AS THE REPORTED WINDS HAVE BEEN VARYING BETWEEN SUSTAINED
HURRICANE FORCE AND LESS THAN 20 KT. THE AIRCRAFT REPORTS INDICATE A
CENTRAL PRESSURE OF 982 MB ALONG WITH 86 KT WINDS AT 700 MB. AN
EYEWALL DROPSONDE INDICATES 91 KT WINDS AT 951 MB. BASED ON
THIS...THE INITIAL INTENSITY IS REDUCED TO 85 KT...AND THIS MIGHT BE
A LITTLE GENEROUS.

LENNY APPEARS TO BE TRAPPED BETWEEN LOW/MID LEVEL RIDGES...AND THERE
APPARENTLY IS A LOW LEVEL TROUGH TO THE NORTH-NORTHEAST OF THE
HURRICANE. A MID/UPPER LEVEL SHORTWAVE TROUGH SEEN IN WATER VAPOR
IMAGERY BETWEEN FLORIDA AND BERMUDA APPEARS WEAK...AND THEREFORE MAY
NOT HAVE AS MUCH IMPACT ON THE MOTION AS THE AVN MODEL OR AVN-BASED
HURRICANE GUIDANCE SUGGESTS. THE UKMET AND NOGAPS HAVE SLOWER
NORTHEASTWARD MOTIONS THAN THE AVN...PERHAPS DUE TO THE WEAKNESS OF
THE TROUGH. THE OFFICIAL FORECAST IS ALONG THE LEFT SIDE OF THE
HURRICANE GUIDANCE...SIMILAR TO BUT SLOWER THAN THE GFDL.

LENNY CONTINUES TO WEAKEN IN SPITE OF WHAT APPEARS TO BE A FAVORABLE
UPPER LEVEL OUTFLOW PATTERN.  HOWEVER...THERE ARE HINTS OF
SOUTHWESTERLY SHEAR UNDERCUTTING THE OUTFLOW.  PROLONGED EXPOSURE TO
THE SAME PATCH OF WATER MAY ALSO BE PLAYING A ROLE IN THE WEAKENING.
THE SHIPS MODEL CONTINUES TO SUGGEST RAPID WEAKENING TO NEAR
MINIMAL HURRICANE STRENGTH IN 24 HOURS...PARTLY DUE TO INCREASED
VERTICAL SHEAR. THE INTENSITY FORECAST CALLS FOR A MORE CONSERVATIVE
WEAKENING...DELAYING RAPID WEAKENING UNTIL LENNY MOVES INTO THE
STRONGER WESTERLIES NORTH OF 20N.
 
BEVEN
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     19/0900Z 18.1N  62.8W    85 KTS
12HR VT     19/1800Z 18.2N  62.4W    80 KTS
24HR VT     20/0600Z 18.4N  61.9W    75 KTS
36HR VT     20/1800Z 18.9N  61.0W    70 KTS
48HR VT     21/0600Z 19.5N  60.0W    65 KTS
72HR VT     22/0600Z 22.0N  58.0W    55 KTS
 
 
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