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HURRICANE LENNY DISCUSSION NUMBER  15
NATIONAL WEATHER SERVICE MIAMI FL
10 PM EST TUE NOV 16 1999
 
A FEW HOURS AGO...A GPS DROPSONDE MEASURED A WIND SPEED OF 126 KNOTS
AT 907 MB IN THE SOUTHEAST EYEWALL.  THE MEAN BOUNDARY LAYER WIND
WAS 101 KNOTS.  A CENTER FIX BY THE NEW WC-130 MODEL J HURRICANE
HUNTER AIRCRAFT SHOWED A CENTRAL PRESSURE OF 958 MB AT 0029Z...
INDICATING A LITTLE MORE DEEPENING.  THE PRESENTATION ON THE SAN
JUAN WSR-88D RADAR IS BECOMING BETTER DEFINED WITH A 25 N MI
DIAMETER EYE SURROUNDED BY A CLOSED WALL.  THE RADAR ALSO MEASURED
CLOUD TOPS TO 60000 FEET IN AN OUTER RAINBAND ABOUT 90 N MI SOUTH OF
THE SOUTHEAST COAST OF PUERTO RICO.  THERE IS STILL THE POSSIBILITY
OF ADDITIONAL STRENGTHENING OF LENNY WITHIN THE NEXT 12 TO 24 HOURS
SINCE VERTICAL SHEAR REMAINS FAIRLY WEAK.  THE OFFICIAL FORECAST
MERELY HOLDS THE WINDS STEADY BECAUSE OF THE UNCERTAINTIES IN
INTENSITY PREDICTION.  LATER IN THE PERIOD...WEAKENING IS EXPECTED
DUE TO AN INCREASINGLY UNFAVORABLE ENVIRONMENT.
 
THE EXPECTED NORTHEASTWARD TURN HAS NOT MATERIALIZED YET.  INITIAL
MOTION IS 070/14.  THE OFFICIAL FORECAST TRACK IS SHIFTED SLIGHTLY
EAST ON ACCOUNT OF THE CONTINUED EAST-NORTHEASTWARD MOTION OVER THE
PAST SEVERAL HOURS.  MOST OF THE MODELS STILL INDICATE A MORE
NORTHEASTWARD MOTION WITHIN 12 TO 24 HOURS...AND THE OFFICIAL
FORECAST IS ROUGHLY IN THE MIDDLE OF THE GUIDANCE ENSEMBLE.  SINCE
THE WESTERN ATLANTIC DEEP-LAYER TROUGH IS EXPECTED TO DE-AMPLIFY
DURING THE NEXT COUPLE OF DAYS...SOME SLOWING OF THE FORWARD SPEED
IS FORECAST.
 
DANGEROUS WINDS EXTEND MUCH FARTHER TO THE SOUTHEAST OF THE
CENTER THAN TO THE NORTHWEST.  THE HURRICANE WARNING IS EXTENDED
EASTWARD AND SOUTHWARD TO INCLUDE ANTIGUA...BARBUDA AND MONTSERRAT.
 
BECAUSE OF THE SIZE OF THE HURRICANE AND THE TRACK FORECAST
UNCERTAINTIES...ONE MUST NOT FOCUS ON THE EXACT FORECAST TRACK.
 
PASCH
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     17/0300Z 16.2N  67.0W   100 KTS
12HR VT     17/1200Z 17.5N  65.2W   100 KTS
24HR VT     18/0000Z 18.9N  63.2W   100 KTS
36HR VT     18/1200Z 20.4N  61.3W    90 KTS
48HR VT     19/0000Z 21.5N  60.0W    80 KTS
72HR VT     20/0000Z 24.0N  58.0W    65 KTS
 
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