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HURRICANE LENNY DISCUSSION NUMBER  12
NATIONAL WEATHER SERVICE MIAMI FL
4 AM EST TUE NOV 16 1999
 
HERE WE GO AGAIN! REPORTS FROM AN AIR FORCE RESERVE HURRICANE HUNTER
AIRCRAFT INDICATE LENNY IS STRENGTHENING WITH A MINIMUM CENTRAL
PRESSURE OF 971 MB AND MAXIMUM 850 MB WINDS OF 109 KT. THE PLANE
ALSO REPORTED A 45 NM WIDE EYE. ALTHOUGH NO EYE IS VISIBLE IN
SATELLITE IMAGERY...THE CLOUD TOPS NEAR THE CENTER ARE -80C TO -85C
AND SATELLITE INTENSITY ESTIMATES ARE AS HIGH AS 102 KT. THE INITIAL
INTENSITY IS SET TO 85 KT...AND THIS MAY BE A BIT CONSERVATIVE.

THE INITIAL MOTION IS 085/13...ALTHOUGH THE TWO AIRCRAFT FIXES HINT
AT A POSSIBLE FASTER MOTION OF 15-16 KT. THE ENVIRONMENT IS LITTLE
CHANGED FROM 24 HOURS AGO...WITH A LARGE DEEP LAYER TROUGH NORTH OF
THE HURRICANE. LARGE SCALE GUIDANCE SUGGESTS A RIDGE SHOULD BUILD
EAST OF THE LESSER ANTILLES...WHICH SHOULD TURN LENNY TO A
NORTHEASTWARD TRACK IN THE NEXT 12-24 HOURS. ALL MODEL FORECASTS ARE
CLUSTERED AROUND A TRACK THROUGH PUERTO RICO AND/OR THE VIRGIN
ISLANDS...WITH THE ONLY DIFFERENCES BEING IN HOW FAST LENNY MOVES.
THE OFFICIAL FORECAST IS SIMILAR TO THE PREVIOUS PACKAGE. IT IS
NOTABLE THAT IF LENNY DOES NOT TURN SOON...THE FORECAST MAY NEED TO
BE ADJUSTED EASTWARD...INCREASING THE THREAT TO THE LEEWARD ISLANDS.
AFTER PASSAGE THROUGH THE ISLANDS...THE NOGAPS AND ECMWF MODELS
BUILD A SHORTWAVE RIDGE NORTH OF LENNY WHICH COULD SLOW THE SYSTEM
DOWN. THIS IS REFLECTED IN THE OFFICIAL FORECAST.

THE FIRST PART OF THE INTENSITY FORECAST IS TRICKY. WITH THE COLD
TOPS AND GENERALLY FAVORABLE OUTFLOW...IT IS POSSIBLE THAT LENNY
COULD BECOME A MAJOR HURRICANE LATER TODAY. ON THE OTHER HAND...THE
RAPID INTENSIFICATION SEEN LAST NIGHT STOPPED RATHER ABRUPTLY DURING
THE DAY. THE INTENSITY FORECAST COMPROMISES BETWEEN THESE TWO
EXTREMES AND TAKES LENNY ACROSS PUERTO RICO AT 95 KT. THINGS ARE
SIMPLER AFTER PASSAGE THROUGH THE ISLANDS...AS A COMBINATION OF
COOLER WATER AND INCREASING VERTICAL SHEAR SHOULD WEAKEN THE
HURRICANE.

BEVEN
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     16/0900Z 15.2N  71.5W    85 KTS
12HR VT     16/1800Z 15.7N  69.9W    90 KTS
24HR VT     17/0600Z 17.0N  67.8W    95 KTS
36HR VT     17/1800Z 18.7N  65.8W    90 KTS
48HR VT     18/0600Z 20.0N  64.0W    85 KTS
72HR VT     19/0600Z 22.5N  61.0W    75 KTS
 
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