529 
 WTNT43 KNHC 270259
 TCDAT3
 TROPICAL STORM LISA DISCUSSION NUMBER  31
 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
 11 PM EDT SUN SEP 26 2004
  
 LISA CONTINUES TO PRODUCE SPORADIC BURSTS OF DEEP CONVECTION ON THE
 NORTHEAST SIDE OF AN OCCASIONALLY-EXPOSED LOW-LEVEL CENTER.  A 2337
 UTC SSMI MICROWAVE PASS SHOWED THAT THE CYCLONE IS A LITTLE FARTHER
 SOUTH THAN THOUGHT AND HAS BEEN MOVING RATHER SLOWLY.  DVORAK
 INTENSITY ESTIMATES HAVE NOT CHANGED WITH A SHEARED TROPICAL
 CYCLONE PATTERN PRESENT SO THE INITIAL INTENSITY REMAINS 45 KT.  
 
 MICROWAVE FIXES INDICATE THE STORM HAS BEEN MOVING GENERALLY TO THE
 NORTH AROUND 5 KT FOR THE PAST 6-12 HOURS. THE OFFICIAL FORECAST IS
 SHIFTED A LITTLE TO THE RIGHT IN THE NEAR-TERM TO ACCOUNT FOR THE
 SLOWER AND MORE NORTHERLY MOTION.A MORE NORTHWESTERLY OR
 NORTH-NORTHWESTERLY MOTION SHOULD COMMENCE SOON DUE TO A MIDDLE-
 LEVEL RIDGE BUILDING TO THE NORTH AND NORTHEAST OF LISA. THE
 FORECAST BEYOND 2 DAYS IS RATHER UNCERTAIN WITH CONSIDERABLE SPREAD
 IN MODEL GUIDANCE. THERE SEEMS TO BE TWO CLUSTERS OF SOLUTIONS
 EMERGING. THE UKMET/GFS MODELS WANT TO RECURVE LISA THRU A BREAK IN
 THE SUBTROPICAL RIDGE ALONG 50W. THE OTHER CLUSTER COMPOSED OF THE
 NOGAPS/GFDN/GFDL SUGGESTS THAT THE STORM WILL NOT RECURVE AND WILL
 INSTEAD TAKE A WESTERLY TURN UNDER A BUILDING RIDGE OVER THE
 WEST-CENTRAL ATLANTIC. IF THE CURRENT SLOW MOTION CONTINUES THE
 MORE WESTERLY MOTION COULD BE CORRECT AS THE RIDGE WOULD HAVE MORE
 TIME TO BUILD TO THE NORTH OF LISA. WITH SO MUCH UNCERTAINTY...THE
 OFFICIAL FORECAST WILL SLOW THE MOTION CONSIDERABLY IN THE MEDIUM-
 RANGE BETWEEN THE TWO CLUSTERS.
 
 IN ADDITION TO ABOUT 15-20 KT OF SOUTHWESTERLY SHEAR...LISA HAS BEEN
 MOVING OVER THE COOL WAKE OF KARL...FURTHER HINDERING ITS
 DEVELOPMENT. LITTLE CHANGE IN STRENGTH IS LIKELY UNTIL AFTER 24
 HOURS WHEN THE STORM MOVES OVER WARMER WATER WITH ABOUT THE SAME
 AMOUNT OF SHEAR. GLOBAL MODEL GUIDANCE SUGGESTS THAT THE SHEAR WILL
 DECREASE IN TWO OR THREE DAYS AS AN UPPER TROUGH CUTS OFF FROM THE
 MID-LATITUDES WEST OF LISA. THIS PATTERN WOULD BE SLIGHTLY MORE
 FAVORABLE FOR INTENSIFICATION OVER WARM WATER NEAR 28C BUT THERE IS
 CONSIDERABLY UNCERTAINTY ON WHERE THE STORM WILL BE AT THAT POINT.
 WITH SO MUCH AMBUIGUITY PRESENT THERE IS NO CHANGE TO THE PREVIOUS
 INTENSITY FORECAST.
  
 FORECASTER BLAKE/STEWART
  
 FORECAST POSITIONS AND MAX WINDS
  
 INITIAL      27/0300Z 19.7N  46.1W    45 KT
  12HR VT     27/1200Z 20.8N  46.4W    45 KT
  24HR VT     28/0000Z 22.4N  47.4W    45 KT
  36HR VT     28/1200Z 24.0N  48.4W    50 KT
  48HR VT     29/0000Z 25.4N  49.1W    55 KT
  72HR VT     30/0000Z 27.5N  50.0W    65 KT
  96HR VT     01/0000Z 29.0N  50.5W    65 KT
 120HR VT     02/0000Z 31.0N  51.0W    65 KT
  
  
 $$