279 
 WTNT44 KNHC 121434
 TCDAT4
 HURRICANE IVAN DISCUSSION NUMBER  41
 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
 11 AM EDT SUN SEP 12 2004
  
 THE INITIAL MOTION ESTIMATE IS 300/8.  IVAN HAS REMAINED ON TRACK...
 SO THERE IS NO SIGNIFICANT CHANGE TO THE PREVIOUS FORECAST TRACK OR
 REASONING. THE LATEST 12Z UPPER-AIR DATA INDICATE A SHARP SHORTWAVE
 TROUGH OVER THE LOWER MISSISSIPPI VALLEY HAS PUSHED SOUTHEASTWARD
 INTO THE CENTRAL GULF OF MEXICO AND HAS ERODED THE RIDGE FROM 500
 MB THROUGH THE 300 MB LEVEL. NHC MODEL GUIDANCE IS IN REASONABLE
 AGREEMENT ON A GRADUAL TURN TO THE NORTHWEST IN 12 TO 24 HOURS...
 WITH A TURN TO THE NORTH AFTER 36 HOURS WHEN IVAN IS EXPECTED TO
 EMERGE OVER THE GULF OF MEXICO NORTH OF WESTERN CUBA. THE OFFICIAL
 FORECAST TRACK IS JUST AN UPDATE OF THE PREVIOUS TRACK AND REMAINS
 IN THE EASTERN PORTION OF THE NHC MODEL GUIDANCE SUITE.
 
 THERE IS NO CHANGE TO THE CURRENT INTENSITY BASED ON RECENT AIR
 FORCE AND NOAA RECON REPORTS. THEREFORE...THERE ALSO REMAINS NO
 CHANGE TO THE PREVIOUS INTENSITY FORECAST TREND. IVAN REMAINS WELL
 ORGANIZED AND THE OUTFLOW HAS IMPROVED TO THE NORTHWEST. THERE WILL
 BE PERIODIC FLUCTUATIONS IN THE INTENSITY DUE TO EYEWALL
 REPLACEMENT CYCLES...LIKE THE ONE IVAN IS CURRENTLY GOING
 THROUGH...BUT LOW SHEAR AND VERY WARM SSTS AHEAD OF THE HURRICANE
 SHOULD AT LEAST KEEP IVAN A CATEGORY FOUR HURRICANE UNTIL EXPECTED
 LANDFALL OCCURS OVER WESTERN CUBA IN ABOUT 24 HOURS OR SO.
 
 BECAUSE STEERING ARE CURRENTLY WEAK AND MAY WEAKEN EVEN MORE...THERE
 REMAINS CONSIDERABLE UNCERTAINTY AS TO JUST WHEN AND WHERE...AND AT
 WHAT INTENSITY...IVAN WILL MAKE LANDFALL IN THE UNITED STATES IN
 THE LONGER TIME PERIODS.
  
 FORECASTER STEWART
  
 FORECAST POSITIONS AND MAX WINDS
  
 INITIAL      12/1500Z 19.0N  81.5W   135 KT
  12HR VT     13/0000Z 19.8N  82.4W   145 KT
  24HR VT     13/1200Z 21.3N  83.5W   145 KT
  36HR VT     14/0000Z 22.9N  84.4W   140 KT
  48HR VT     14/1200Z 24.7N  85.0W   125 KT
  72HR VT     15/1200Z 28.3N  85.5W   110 KT
  96HR VT     16/1200Z 32.5N  84.5W    55 KT...INLAND
 120HR VT     17/1200Z 37.0N  81.5W    25 KT...INLAND
  
  
 $$