266 
 WTNT43 KNHC 240858
 TCDAT3
 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
  
  
 $$