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HURRICANE LILI DISCUSSION NUMBER 38
NATIONAL WEATHER SERVICE MIAMI FL
11 PM EDT MON SEP 30 2002
LILI CONTINUES TO LOOK MORE IMPRESSIVE IN SATELLITE IMAGERY WITH THE
CENTER NOW EMBEDDED IN THE MIDDLE OF A VERY COLD-TOPPED CENTRAL
DENSE OVERCAST FEATURE. SATELLITE INTENSITY ESTIMATES ARE T4.5...OR
77 KT FROM BOTH TAFB AND AFWA...WHILE 3-HR OBJECTIVE DVORAK
T-NUMBERS ARE ABOUT 80 KT...OR T4.8. HOWEVER...NONE OF THIS APPEARS
TO BE TRANSLATING DOWN TO THE SURFACE AS AN INCREASE IN WIND SPEED.
WHILE THE SURFACE PRESSURE OF 978 MB SUPPORTS ABOUT 78 KT...THE
INITIAL INTENSITY WAS HELD AT 70 KT BASED ON A 700 MB FLIGHT-LEVEL
WIND OF 77 KT AND A 934 MB DROPSONDE WIND OF 94 KT. THESE WINDS
CORRESPOND TO APPROXIMATELY 69 KT AND 71 KT SURFACE WINDS...
RESPECTIVELY. UPPER-LEVEL OUTFLOW IS EXCELLENT IN THE SOUTHERN
SEMICIRCLE AND FAIR TO GOOD TO THE NORTH.
THE INITIAL MOTION REMAINS 300/9. LILI APPEARS TO HAVE STEADIED ON
THIS GENERAL COURSE AND IT LOOKS LIKE THERE WILL BE LITTLE DEVIATION
ABOUT THIS MEAN COURSE FOR THE NEXT 36 TO 48 HOURS. THE DEEP LAYER
SUBTROPICAL RIDGE THAT EXTENDS FROM BERMUDA ACROSS THE SOUTHEAST
UNITED STATES IS FORECAST TO REMAIN IN PLACE THROUGHOUT THE FORECAST
PERIOD. THE 500 MB RIDGE AXIS IS FORECAST TO LIE ALONG 31-32N
LATITUDE AND SHOULD BE THE AXIS OF RECURVATURE AT OR BEYOND 72
HOURS. THE NHC MODEL GUIDANCE REMAINS REMARKABLY CONVERGENT ON A
TRACK ACROSS EXTREME WESTERN CUBA IN ABOUT 18 HOURS AND THEN ENDING
UP NEAR THE SOUTHWEST COAST OF LOUISIANA IN 72 HOURS. THE ONLY
UNNERVING PART OF THE MODEL GUIDANCE IS THE GFS/AVN 10-MEMBER
ENSEMBLE MODEL WHICH TAKES LILI DUE NORTH AFTER 48 HOURS TO A
POSITION JUST SOUTH OF NEW ORLEANS. WATER VAPOR IMAGERY INDICATES
THE DEEP MID- TO UPPER-LEVEL TROUGH OVER THE WESTERN U.S. CONTINUES
TO DIG SOUTHWARD. MORE AMPLIFICATION OF THE TROUGH THAN THE GLOBAL
MODELS ARE INDICATING COULD CAUSE THE SUBTROPICAL RIDGE OVER THE
SOUTHEAST U.S. TO LIFT A LITTLE MORE NORTHWARD. THE INCREASING
SOUTHWESTERLY MID-LEVEL FLOW AHEAD OF THE TROUGH COULD ALSO PUSH
LILI A LITTLE MORE INTO THE WESTERN PERIPHERY OF THE RIDGE...MAKING
THE GFS/AVN ENSEMBLE MODEL A VIABLE FORECAST. THE OFFICIAL FORECAST
TRACK IS JUST AN EXTENSION OF THE PREVIOUS FORECAST TRACK THROUGH 48
HOURS...WITH JUST A SLIGHT SHIFT EASTWARD AT 72 HOURS OUT OF RESPECT
FOR THE GFS/AVN ENSEMBLE MODEL.
THE CENTRAL PRESSURE HAS DECREASED 6 MB IN THE PAST 6 HOURS...SO
LILI MAY BE STARTING TO RAPIDLY INTENSIFY. THE SATELLITE SIGNATURES
ALSO SUGEGST THIS...SO THE INTENSIFICATION RATE WAS INCREASED DURING
THE NEXT 12 HOURS...AFTER WHICH LAND INTERACTION WITH CUBA SHOULD
DISRUPT THE STRENGTHENING PROCESS. THE WATER OVER THE GULF OF MEXICO
HAS BEEN CHURNED UP PRETTY GOOD BY FORMER HURRICANE ISIDORE...BUT
THE WATER IS WARM ENOUGH FOR CONTINUED INTENSIFICATION AND ALSO
SUPPORTS MAJOR HURRICANE INTENSITY. THE GFDL MODEL NOW BRINGS LILI
TO 103 KT IN ABOUT 60 HOURS. THE FSU SUPERENSEMBLE BRINGS LILI UP TO
148 KT IN 72 HOURS...WHICH SEEMS MUCH TOO HIGH GIVEN THE COLD
UPWELLING THAT HAS OCCURRED IN THE WAKE OF ISIDORE.
FORECASTER STEWART
FORECAST POSITIONS AND MAX WINDS
INITIAL 01/0300Z 20.7N 81.5W 70 KTS
12HR VT 01/1200Z 21.8N 83.2W 85 KTS
24HR VT 02/0000Z 23.1N 85.8W 90 KTS
36HR VT 02/1200Z 24.5N 88.3W 95 KTS
48HR VT 03/0000Z 25.8N 90.8W 100 KTS
72HR VT 04/0000Z 29.5N 93.0W 105 KTS
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