[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT43 KNHC 241445
TCDAT3
TROPICAL DEPRESSION LISA DISCUSSION NUMBER  21
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
11 AM EDT FRI SEP 24 2004

EARLY MORNING VISIBLE SATELLITE IMAGERY SHOWED THAT THE CENTER OF
THE TROPICAL CYCLONE WAS NEAR THE NORTH EDGE OF THE DEEP
CONVECTION...AND AN 0852 UTC QUIKSCAT DATA SUGGESTED THAT LISA WAS
LIKELY A TROPICAL STORM OVERNIGHT.  12Z DVORAK INTENSITY ESTIMATES
WERE 35 KT FROM ALL AGENCIES.  HOWEVER...SINCE THEN THE LOW LEVEL
CENTER HAS ONCE AGAIN BECOME EXPOSED AND IS NOW LOCATED ABOUT 70 NM
NORTH OF THE CONVECTION.  THEREFORE LISA WILL REMAIN A 30 KT
TROPICAL DEPRESSION FOR THIS ADVISORY.

THE CENTER HAS BEEN RELOCATED SOUTHWARD BASED ON VISIBLE SATELLITE
IMAGERY. THE INITIAL MOTION IS HARD TO DETERMINE...BUT 24 HOUR
SATELLITE LOOPS SUGGEST THAT LISA COMPLETED ITS ORIGINAL CYCLONIC
LOOP LATE YESTERDAY AND THEN MOVED WEST-SOUTHWESTWARD FOR A TIME
OVERNIGHT. IT IS ASSUMED THAT A WEST-NORTHWEST MOTION WILL RESUME
SHORTLY AND THE INITIAL MOTION IS ESTIMATED TO BE 285/7 KT.

THE FORECAST TRACK REMAINS SIMILAR TO THE PREVIOUS ONE THROUGH 72
HOURS.  THE RIDGE NORTH OF LISA WILL CONTINUE TO WEAKEN AS A LARGE
MID/UPPER LEVEL TROUGH MOVES SOUTHEAST INTO THE CENTRAL ATLANTIC.
THIS SHOULD TURN LISA NORTHWESTWARD AND NORTHWARD DURING THE NEXT 48
TO 72 HOURS.  IN THE LONGER RANGE...THE GFS AND GFDL INDICATE THAT
THE TROUGH MAY NOT COMPLETELY PICK UP THE CYCLONE WHILE THE NOGAPS
AND UKMET ARE MUCH FASTER AND FURTHER NORTHEAST.  THE OFFICIAL
TRACK INDICATES A SOMEWHAT SLOWER MOTION AT 96 AND 120 HOURS THAN
THE PREVIOUS ADVISORY AND LEANS A LITTLE CLOSER TO THE GFS/GFDL
SOLUTION.

GLOBAL MODELS SUGGESTS THAT THE NORTHERLY SHEAR SHOULD WEAKEN A
LITTLE DURING THE NEXT 24-36 HOURS. THE OFFICIAL FORECAST CALLS FOR
SLOW STRENGTHENING THROUGH 72 HOURS THEN LEVELS OFF THE INTENSITY
AS LISA IS EXPECTED TO ENCOUNTER SOUTHWESTERLY SHEAR AHEAD OF THE
MID/UPPER LEVEL TROUGH.  THE INTENSITY FORECAST IS NOT NEARLY AS
AGGRESSIVE AS THE SHIPS MODEL...WHICH BRINGS LISA TO A HURRICANE IN
60 HOURS.  THE 12Z RUN OF THIS MODEL WAS ALSO INITIALIZED WHEN LISA
APPEARED TO BE STRONGER THAN IT DOES NOW.

FORECASTER BROWN/FRANKLIN

FORECAST POSITIONS AND MAX WINDS

INITIAL      24/1500Z 14.1N  43.3W    30 KT
 12HR VT     25/0000Z 14.8N  44.3W    30 KT
 24HR VT     25/1200Z 16.3N  45.5W    35 KT
 36HR VT     26/0000Z 17.8N  46.2W    40 KT
 48HR VT     26/1200Z 19.8N  46.7W    50 KT
 72HR VT     27/1200Z 24.0N  46.4W    55 KT
 96HR VT     28/1200Z 28.0N  45.0W    55 KT
120HR VT     29/1200Z 31.5N  43.5W    55 KT


$$This weather bulletin was brought to you by:
www.nashvilleweather.net