Tropical Storm LISA

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TROPICAL STORM LISA DISCUSSION NUMBER  25
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
11 AM EDT SAT SEP 25 2004
 
EARLY MORNING VISIBLE SATELLITE IMAGERY INDICATES THAT THE LOW LEVEL
CENTER REMAINS EXPOSED TO THE WEST OF THE DEEP CONVECTION.
HOWEVER...IN THE LAST COUPLE HOURS A CONVECTIVE BAND HAS TRIED TO
WRAP AROUND THE EAST SIDE OF THE CIRCULATION. CURRENT DVORAK
INTENSITY ESTIMATES ARE 35 KT FROM ALL AGENCIES. LISA WILL REMAIN A
35 KT TROPICAL STORM. WIND RADII WERE EXPANDED A LITTLE BASED UPON A
RECENT QUIKSCAT OVERPASS.

INITIAL MOTION IS 320/8 KT. THE FORECAST REASONING REMAINS THE SAME
FOR THE NEXT 72 HOURS. A LARGE MID/UPPER LEVEL TROUGH OVER THE
CENTRAL ATLANTIC HAS WEAKENED THE SUBTROPICAL RIDGE WHICH WILL ALLOW
LISA TO MOVE IN A NORTHWEST DIRECTION. LATER IN THE FORECAST PERIOD
THE GLOBAL MODELS ARE INDICATING A TURN BACK TO THE WEST-NORTHWEST.
THE MODELS INDICATE THAT THE TROUGH WILL LIFT OUT WITH A MID-LEVEL
RIDGE IS EXPECTED TO BUILD ACROSS THE CENTRAL ATLANTIC. THIS IS THE
SAME RIDGE THAT IS CURRENTLY STEERING HURRICANE JEANNE. THE
UKMET...MOVES LISA SLOWER DURING THE EARLY PART OF THE FORECAST
PERIOD AND THEREFORE TURNS THE CYCLONE MUCH SOONER AND IS FURTHER
SOUTH. THE OFFICIAL FORECAST WAS ADJUSTED TO THE LEFT OF THE
PREVIOUS TRACK AND IS BETWEEN THE GLOBAL MODEL CONSENSUS AND THE
GFS SOLUTION. 

SHIPS MODEL WAS INITIALIZED WITH NORTHERLY SHEAR OF 17 KT OVER 
LISA. WATER VAPOR IMAGERY SUGGESTS THAT THE SHEAR MAY BE 
BEGINNING TO LESSON. THEREFORE...THE OFFICIAL FORECAST CALLS FOR
SLOW STRENGTHENING THROUGH 72 HOURS. SHIPS MODEL INDICATES THAT THE
SHEAR MAY REMAIN LOW BEYOND 72 HOURS ALLOWING LISA TO BECOME A
HURRICANE. HOWEVER...THE OFFICIAL FORECAST WILL REMAIN CONSERVATIVE
AND LEVEL OFF LISA JUST BELOW HURRICANE STRENGTH.
 
FORECASTER BROWN/AVILA
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      25/1500Z 15.9N  45.6W    35 KT
 12HR VT     26/0000Z 16.8N  46.4W    40 KT
 24HR VT     26/1200Z 18.0N  47.2W    45 KT
 36HR VT     27/0000Z 19.4N  47.9W    50 KT
 48HR VT     27/1200Z 21.0N  48.5W    55 KT
 72HR VT     28/1200Z 23.7N  50.0W    60 KT
 96HR VT     29/1200Z 25.5N  51.5W    60 KT
120HR VT     30/1200Z 27.0N  54.0W    60 KT
 
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