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HURRICANE LENNY DISCUSSION NUMBER  11
NATIONAL WEATHER SERVICE MIAMI FL
10 PM EST MON NOV 15 1999

THERE IS NO EYE EVIDENT EITHER ON MICROWAVE OR INFRARED IMAGERY AND
THE OVERALL CLOUD PATTERN...EVEN THOUGH IT CONTAINS CONSIDERABLE AND
VERY DEEP CONVECTION...IS NOT THAT WELL ORGANIZED.  EARLIER RECON
DATA IMPLIED CONSIDERABLE WEAKENING AND CURRENT DVORAK DATA T-
NUMBERS ARE ALSO DOWN FROM WHERE THEY WERE EARLIER TODAY.  CURRENT
INTENSITY IS REDUCED TO 70 KNOTS.  WE DO NOT UNDERSTAND WHY LENNY
WEAKENED TODAY...EXCEPT THAT ITS VERY SMALL INNER CORE REGION MAY BE
VERY SENSITIVE TO SUBTLE ENVIRONMENTAL CHANGES.  DROPSONDE DATA FROM
THE NOAA G-IV JET MISSION THIS EVENING SHOW A FAIRLY IMPRESSIVE
UPPER-TROPOSPHERIC OUTFLOW PATTERN BUT THIS SEEMS TO BE CONFINED TO
A SHALLOWER LAYER...AROUND 200 MB...THAN WE NORMALLY SEE.  BOTH THE
SHIPS AND THE TRIPLY-NESTED GFDL MODEL INDICATE THAT SOME RE-
STRENGTHENING COULD OCCUR...AND THIS IS ALLOWED FOR IN THE OFFICIAL
FORECAST.

CENTER FIXES ARE RATHER UNCERTAIN...BUT USING A BLEND OF INFRARED
AND MICROWAVE-BASED POSITION ESTIMATES...INITIAL MOTION ESTIMATE IS
080/12.  THE OFFICIAL TRACK FORECAST IS QUITE SIMILAR TO THE
PREVIOUS ONE.  LENNY IS LIKELY TO BE STEERED BY THE FLOW AROUND THE
SOUTHERN PORTION OF A DEEP-LAYER TROUGH.  WIND DATA FROM THE G-IV
SUPPORT THIS SCENARIO AS WELL.  THE NCEP GLOBAL MODEL SHOWS SOME
AMPLIFICATION OF A MID-TROPOSPHERIC ANTICYCLONE TO THE EAST OF THE
LEEWARD ISLAND IN 2-3 DAYS.  THIS SHOULD CAUSE A MORE NORTHEASTWARD
TRACK IN THE LATTER PART OF THE PERIOD.

SINCE THE FORECAST TRACK AND WIND RADII BRING TROPICAL STORM FORCE
WINDS TO PUERTO RICO IN 24 HOURS...IT IS PRUDENT TO ISSUE HURRICANE
WARNINGS FOR THAT AREA AT THIS TIME.  THE SLIGHTLY LARGER EXTENT OF
34-KNOT WINDS TO THE NORTH SHOWN ON THIS ADVISORY ALSO NECESSITATES
THE ISSUANCE OF A TROPICAL STORM WARNING FOR THE SOUTH COAST OF THE
DOMINICAN REPUBLIC.

PASCH
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     16/0300Z 15.2N  73.0W    70 KTS
12HR VT     16/1200Z 15.5N  71.1W    75 KTS
24HR VT     17/0000Z 16.6N  68.9W    80 KTS
36HR VT     17/1200Z 18.0N  67.0W    80 KTS
48HR VT     18/0000Z 19.5N  65.0W    80 KTS
72HR VT     19/0000Z 22.0N  62.0W    75 KTS
 
 
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