863 
 WTNT44 KNHC 242045
 TCDAT4
 TROPICAL STORM LISA DISCUSSION NUMBER  16
 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL142010
 500 PM AST FRI SEP 24 2010
  
 CONVENTIONAL AND MICROWAVE SATELLITE IMAGERY INDICATES LISA HAS
 CONTINUED TO BECOME BETTER ORGANIZED AND HAS STRENGTHENED. A RECENT
 TRMM OVERPASS REVEALED A CLOSED LOW-LEVEL EYE WITH A DIAMETER OF
 ABOUT 8-10 NMI...AND VISIBLE AND INFRARED IMAGERY HAVE BEEN HINTING
 THAT AN EYE HAS ALSO BEEN TRYING TO FORM. THE INITIAL INTENSITY OF
 50 KT IS BASED ON A BLEND OF SATELLITE ESTIMATES OF T3.0/45 KT FROM
 BOTH TAFB AND SAB...TAFB AODT ESTIMATES OF T3.4/53 KT...AND
 UW-CIMSS 3-HR AVERAGE ADT ESTIMATES OF T3.4/53 KT. GIVEN THE VERY
 SMALL SIZE OF THE INNER-CORE CIRCULATION...WHICH RESTRICTS THE
 VARIOUS SATELLITE INTENSITY TECHNIQUES...IT IS POSSIBLE THAT LISA
 COULD BE STRONGER THAN INDICATED IN THIS ADVISORY.
  
 THE INITIAL MOTION ESTIMATE IS 360/07. FOR THE NEXT 24-36 HOURS...
 LISA IS FORECAST TO MOVE NORTHWARD AROUND THE WESTERN PERIPHERY OF
 THE LARGE SAHARAN SUBTROPICAL RIDGE LOCATED TO THE EAST OF THE
 CYCLONE. BY 48 HOURS...LISA IS EXPECTED TO MOVE INTO AN ENVIRONMENT
 OF STRONG SOUTHWESTERLY SHEAR FORECAST TO DEVELOP AHEAD OF A
 SHORTWAVE TROUGH CURRENTLY DIGGING SOUTHEASTWARD OVER THE CENTRAL
 ATLANTIC. THE EXPECTED RESULT IS THAT THE LOW-LEVEL AND UPPER-LEVEL
 CIRCULATIONS WILL DECOUPLE IN 72-96 HOURS...WITH THE LOW-LEVEL
 CIRCULATION MOVING NORTH-NORTHWESTWARD OR EVEN NORTHWESTWARD AS A
 REMNANT LOW PRESSURE SYSTEM THAT WILL BE STEERED BY THE LARGE
 SURFACE BERMUDA HIGH LOCATED OVER THE CENTRAL ATLANTIC. IN
 CONTRAST...THE GFDL AND HWRF MODELS MOVE LISA NORTHEASTWARD AFTER
 72 HOURS AS A SIGNIFICANT TROPICAL CYCLONE. THOSE SCENARIOS ARE
 BEING DISCOUNTED AT THIS TIME DUE TO THEIR KNOWN BIAS IN RESISTING
 STRONG VERTICAL SHEAR CONDITIONS. THE OFFICIAL FORECAST TRACK IS A
 LITTLE TO THE RIGHT OF THE PREVIOUS ADVISORY...AND IS CLOSE TO THE
 NHC CONSENSUS MODEL...TVCN.
  
 SATELLITE IMAGERY SHOWS MODERATE CONVECTION OCCURRING AT LEAST 200
 NMI TO THE NORTH OF LISA. THIS INDICATES THAT THERE IS AVAILABLE
 INSTABILITY FOR THE CYCLONE TO TAP IN TO DESPITE THE SUB-26C SSTS
 THAT LIE AHEAD OF THE SYSTEM. AS A RESULT...SOME ADDITIONAL
 STRENGTHENING IS EXPECTED DURING THE NEXT 12-24 HOURS...AND IT IS 
 POSSIBLE THAT LISA COULD BECOME A HURRICANE. HOWEVER...BY 36 HOURS
 LISA IS FORECAST TO ENCOUNTER STRONG SHEAR OF MORE THAN 30 KT...
 WHICH SHOULD INDUCE STEADY WEAKENING. LISA IS FORECAST TO DEGENERATE
 INTO A REMNANT LOW PRESSURE SYSTEM BY 96 HOURS AND DISSIPATE BY 120
 HOURS. THE OFFICIAL INTENSITY FORECAST IS SIMILAR TO A BLEND OF THE
 SHIPS AND LGEM INTENSITY MODELS AT ALL TIMES.
 
  
 FORECAST POSITIONS AND MAX WINDS
  
 INITIAL      24/2100Z 20.0N  27.8W    50 KT
  12HR VT     25/0600Z 21.0N  28.0W    55 KT
  24HR VT     25/1800Z 22.5N  28.3W    50 KT
  36HR VT     26/0600Z 24.1N  28.7W    45 KT
  48HR VT     26/1800Z 25.3N  29.1W    35 KT
  72HR VT     27/1800Z 27.3N  29.9W    30 KT
  96HR VT     28/1800Z 29.0N  30.5W    25 KT...POST-TROP/REMNT LOW
 120HR VT     29/1800Z...DISSIPATED
  
 $$
 FORECASTER STEWART