Tropical Storm LISA

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TROPICAL DEPRESSION LISA DISCUSSION NUMBER  20
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
5 AM EDT FRI SEP 24 2004
 
SHORTWAVE AND ENHANCED BD INFRARED IMAGERY SUGGEST THAT THE
PREVIOUSLY EXPOSED LOW-LEVEL CIRCULATION CENTER HAS BEGUN TO MOVE
BENEATH THE NORTHEASTERN EDGE OF THE DEVELOPING DEEP CONVECTION.
THIS LEADS US TO BELIEVE THAT THE NORTHERLY SHEAR MAY BE DECREASING
SOMEWHAT. DVORAK CURRENT SATELLITE INTENSITY ESTIMATES ARE 35 KT
FROM TAFB AND 30 KT FROM SAB. THE INITIAL INTENSITY WILL REMAIN AT
30 KT BASED PRIMARILY ON A 24/0511Z TRMM OVERPASS WHICH INDICATED A
POORLY DEFINED LOW CENTER. SHIPS SUGGESTS WEAKENING OF THE
NORTHERLY SHEAR DURING THE NEXT 48 HOURS. AFTER THE 48 HOUR
PERIOD...THE INTENSITY MODEL INDICATES THAT LISA WILL ENCOUNTER
INCREASING SOUTHWESTERLY SHEAR AHEAD OF AN APPROACHING MID/UPPER
TROUGH FROM THE NORTHWEST...BUT NOT SIGNFICANT ENOUGH TO PREVENT
FURTHER INTENSIFICATION. THE GFS ON THE OTHER HAND INDICATES
STRONGER SOUTHWESTERLY SHEAR AT THE SAME TIMEFRAME AND OPENS THE
TROPICAL CYCLONE INTO A WAVE. THE OFFICIAL FORECAST CALLS FOR
GRADUAL STRENGTHENING THROUGH THE ENTIRE FORECAST AND IS BASED
PRIMARILY ON THE SHIPS MODEL.
 
INITIAL MOTION IS 280/9 KT. THERE IS NO CHANGE TO THE TRACK FORECAST
REASONING FROM THE PREVIOUS PACKAGE. A WEAKENING RIDGE TO THE NORTH
SHOULD INFLUENCE A WEST-NORTHWEST MOTION DURING THE NEXT 24 HOURS.
THEREAFTER AN APPROACHING MID LEVEL TROUGH SHOULD INDUCE A TURN
TOWARD THE NORTHWEST AND NORTH-NORTHWEST. THE OFFICIAL FORECAST IS
SLIGHTLY TO THE LEFT OF THE PREVIOUS FORECAST AND IS BASED ON THE
CONU CONSENSUS.
 
FORECASTER ROBERTS/BEVEN
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      24/0900Z 14.6N  43.5W    30 KT
 12HR VT     24/1800Z 15.2N  44.6W    35 KT
 24HR VT     25/0600Z 16.5N  45.7W    40 KT
 36HR VT     25/1800Z 18.0N  46.5W    45 KT
 48HR VT     26/0600Z 19.5N  47.2W    55 KT
 72HR VT     27/0600Z 23.5N  47.5W    55 KT
 96HR VT     28/0600Z 28.0N  46.0W    60 KT
120HR VT     29/0600Z 33.0N  43.5W    60 KT
 
 
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