HOME	ACTIVE CYCLONES	FORECASTS	IMAGERY	ABOUT TPC	RECONNAISSANCE

ZCZC MIATCDAT1 ALL
TTAA00 KNHC DDHHMM
HURRICANE LENNY DISCUSSION NUMBER  23
NATIONAL WEATHER SERVICE MIAMI FL
10 PM EST THU NOV 18 1999
 
INFORMATION FROM DUTCH ST. MAARTEN THIS EVENING INCLUDES AN
UNOFFICIAL REPORT OF 100 MPH FROM A SHIP IN SIMSON BAY...AND
MULTIPLE REPORTS OF CALM WINDS...INDICATING THAT A PORTION OF THE
EYE PASSED OVER THE ISLAND.  MORE RECENTLY THE WIND HAS BEGUN TO
PICK UP FROM THE SOUTHWEST...BUT AT SPEEDS THAT SUGGEST THEY ARE NOT
YET FULLY IN THE SOUTHERN EYEWALL...AS THE CALM IS NOW BEING
REPORTED IN ANGUILLA.  THE MOST RECENT RECONNAISSANCE REPORTS SHOW
THAT THE MINIMUM PRESSURE CONTINUES TO RISE...UP 23 MB IN TWELVE
HOURS...AND THE MAXIMUM WINDS CONTINUE TO FALL.  THE AIRCRAFT
REPORTED 107 KT AND ON THIS BASIS THE INTENSITY IS LOWERED
TO 95 KT.  THIS BRINGS LENNY DOWN TO CATEGORY TWO STATUS ON THE
SAFFIR/SIMPSON SCALE.

LENNY HAS BEEN MEANDERING OVER THE PAST FEW HOURS. MODEL GUIDANCE IS
WIDELY DIVERGENT THIS EVENING...WITH AN IMPORTANT DISAGREEMENT
BETWEEN THE UKMET AND THE AVN.  BOTH MODELS INITIALIZE A MID-LEVEL
TROUGH OFF THE SOUTHEASTERN STATES.  WHILE THE AVN BRINGS A PIECE OF
THIS TROUGH SOUTHEASTWARD...RESULTING IN AN ACCELERATION OF LENNY
AWAY FROM THE ISLANDS...THE UKMET KEEPS THE TROUGH AWAY FROM THE
CYCLONE.  THIS RESULTS IN A MUCH SLOWER...AND LESS EASTWARD MOTION
OVER THE NEXT THREE DAYS.  IN ADDITION...THE AVN ANALYZES ANOTHER
VORTEX ABOUT 400 NM NORTHEAST OF LENNY WHICH APPEARS TO CONTRIBUTE
TO THE ACCELERATION.  INTERESTINGLY...THE UKMET HAS BEEN MUCH CLOSER
TO THE ACTUAL TRACK OVER THE PAST FEW DAYS THAN THE AVN-BASED
GUIDANCE.  IN VIEW OF THIS...THE OFFICIAL FORECAST IS A COMPROMISE
BETWEEN THE PREVIOUS FORECAST AND THE UKMET.  

LENNY HAS BEEN WEAKENING IN SPITE OF WHAT APPEARS TO BE A FAVORABLE
UPPER LEVEL OUTFLOW PATTERN.  THERE ARE SOME HINTS OF SOUTHWESTERLY
SHEAR UNDERCUTTING THE OUTFLOW HOWEVER.  PROLONGED EXPOSURE TO THE
SAME PATCH OF WATER MAY ALSO BE PLAYING A ROLE IN THE WEAKENING. 
THE SHIPS INTENSITY FORECAST MODEL SUGGESTS RAPID WEAKENING TO NEAR
MINIMAL HURRICANE STRENGTH IN 24 HOURS...BUT THIS IS BASED ON THE
AVN FORECAST SHEAR WHICH MAY NOT VERIFY.  I AM FORECASTING CONTINUED
SLOW WEAKENING.

FRANKLIN
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     19/0300Z 18.2N  63.1W    95 KTS
12HR VT     19/1200Z 18.3N  62.8W    90 KTS
24HR VT     20/0000Z 18.7N  62.2W    85 KTS
36HR VT     20/1200Z 19.4N  61.4W    80 KTS
48HR VT     21/0000Z 20.5N  60.0W    75 KTS
72HR VT     22/0000Z 23.0N  58.5W    70 KTS
 
 
NNNN