[Tropical] Tropical Cyclone Discussion

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WTNT43 KNHC 220832
TCDAT3
TROPICAL STORM LISA DISCUSSION NUMBER  12
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
5 AM EDT WED SEP 22 2004

THE SYSTEM CONTINUES AS A RATHER SMALL...AMORPHOUS...BLOB OF DEEP
CONVECTION ON SATELLITE IMAGES.  ALTHOUGH THE CLOUD TOPS ARE VERY
COLD...THERE IS LITTLE ORGANIZATION OTHER THAN A CONCENTRATION NEAR
THE CENTER.  BASED ON DVORAK CLASSIFICATIONS... THE INTENSITY IS
ADJUSTED DOWNWARD SLIGHTLY.  THERE IS SOME CONCERN ABOUT HOW THE
EVOLUTION OF THE STORM WILL BE AFFECTED BY THE DISTURBANCE TO ITS
EAST-SOUTHEAST.  THE LATTER SYSTEM COULD ALSO BECOME A TROPICAL
CYCLONE...AND WOULD PROBABLY BE A LARGER ONE THAN LISA.  THUS IT IS
POSSIBLE THAT THE LARGER SYSTEM COULD ABSORB LISA.  OTHERWISE THE
ENVIRONMENT IS MARGINALLY FAVORABLE FOR STRENGTHENING.  THE
OFFICIAL FORECAST SHOWS SOME STRENGTHENING BUT IS BELOW THE SHIPS
GUIDANCE BEYOND 2 DAYS BECAUSE OF THE POTENTIALLY UNFAVORABLE
INFLUENCE OF THE SYSTEM TO THE EAST.

IT IS NOT EASY TO LOCATE THE CENTER...BUT...BECAUSE OF THE MODERATE
EAST-NORTHEASTERLY SHEARING ENVIRONMENT...IT IS ESTIMATED TO BE
NEAR THE EASTERN EDGE OF THE DENSE OVERCAST.  THE INITIAL MOTION IS
ESTIMATED TO BE 285/6.  TRACK GUIDANCE IS FAR FROM
STRAIGHTFORWARD...WITH CONSIDERABLE SCATTER AMONG THOSE DYNAMICAL
MODELS THAT ARE ABLE TO TRACK A CENTER IN THEIR FORECAST FIELDS.
THE GFDL MODEL SHOWS A SHARP SOUTHWARD TURN FOLLOWED BY A SHARP
NORTHWARD TURN.  THE NOGAPS SHOWS ERRATIC MOTION...AND THE GFS
LOSES THE VORTEX IN ITS OUTPUT.  ONLY THE U.K. MET OFFICE MODEL
TRACK IS SOMEWHAT CLIMATOLOGICAL...SINCE IT DEPICTS A GRADUAL TURN
TO THE NORTHWEST.  THAT DOES NOT SEEM TO BE AN UNREASONABLE
SCENARIO...SINCE I DO NOT EXPECT LISA TO HAVE MUCH OF A MID-LEVEL
RIDGE TO ITS NORTH OVER THE NEXT SEVERAL DAYS.  GIVEN THE
UNCERTAINTIES AND DIVERGENCE IN THE MODEL OUTPUT...THE OFFICIAL
FORECAST IS EVEN SLOWER THAN THE PREVIOUS ONE.

FORECASTER PASCH

FORECAST POSITIONS AND MAX WINDS

INITIAL      22/0900Z 14.5N  41.2W    55 KT
 12HR VT     22/1800Z 14.8N  42.0W    55 KT
 24HR VT     23/0600Z 15.2N  43.2W    55 KT
 36HR VT     23/1800Z 15.6N  44.3W    60 KT
 48HR VT     24/0600Z 15.8N  45.0W    65 KT
 72HR VT     25/0600Z 16.5N  46.5W    70 KT
 96HR VT     26/0600Z 17.5N  48.0W    70 KT
120HR VT     27/0600Z 18.5N  49.0W    70 KT

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