944 
 WTNT44 KNHC 141457
 TCDAT4
 HURRICANE IVAN DISCUSSION NUMBER  49
 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
 11 AM EDT TUE SEP 14 2004
  
 RECONNAISSANCE REPORTS AND SATELLITE IMAGERY INDICATE THAT IVAN HAS
 WEAKENED SOMEWHAT THIS MORNING.  THE CENTRAL PRESSURE IN THE
 CLOUD-FILLED EYE WAS UP TO 932 MB AND THE PEAK 700 MB WINDS HAVE
 COME DOWN TO 128 KT.  BASED ON THESE OBSERVATIONS...THE ADVISORY
 INTENSITY IS LOWERED TO 120 KT AND EVEN THIS ESTIMATE IS PROBABLY A
 BIT HIGH.  THIS WEAKENING IS CONCURRENT WITH THE EROSION OF THE
 EYEWALL REPORTED BY THE AIRCRAFT CREW AND THE DEVELOPMENT OF A NEW
 EYEWALL ABOUT 40-50 NM ACROSS.
 
 WATER VAPOR IMAGERY AND DATA FROM THE NOAA G-IV JET THIS MORNING
 CONTINUE TO INDICATE RESTRICTION OF THE OUTFLOW IN THE NORTHWEST
 QUADRANT OF THE HURRICANE...AS WELL AS VERY DRY AIR UNDERNEATH THE
 CIRRUS CANOPY.  THIS...ALONG WITH THE CURRENT EYEWALL REPLACEMENT
 CYCLE...SUGGESTS THAT IVAN MAY CONTINUE TO WEAKEN A BIT DURING THE
 NEXT 12 HOURS OR SO.  AFTER THAT...GLOBAL MODELS SUGGEST A
 RELAXATION OF THE WESTERLY SHEAR ABOUT THE TIME THAT IVAN IS
 EXPECTED TO PASS OVER A WARM EDDY IN THE CENTRAL GULF.  THIS COULD
 ALLOW IVAN TO REGAIN SOME STRENGTH BEFORE LANDFALL...AND THIS IS
 REFLECTED IN THE OFFICIAL FORECAST.  THERE HAS BEEN NO CHANGE FROM
 THE BASIC EXPECTATION THAT IVAN WILL BE A MAJOR HURRICANE AT
 LANDFALL.
 
 THE INITIAL MOTION IS 330/7.  IVAN IS MOVING AROUND THE PERIPHERY OF
 THE ATLANTIC SUBTROPICAL RIDGE.  A SECOND MID-LEVEL HIGH IS
 CENTERED OVER LOUISIANA WITH A RIDGE EXTENDING SOUTHWARD INTO THE
 WESTERN GULF OF MEXICO.  12Z RAOBS AND JET DATA INDICATE THAT THIS
 LATTER RIDGE IS A LITTLE STRONGER THAN FORECAST BY THE 6Z GFS RUN.  
 THIS MIGHT RESULT IN WEAKER STEERING AND A SLOWER MOTION TOWARD THE
 COAST THAN THE GFS IS FORECASTING.  MODEL GUIDANCE IS IN PRETTY
 GOOD AGREEMENT THROUGH 48 HOURS...WITH ONLY ABOUT 125 MILES
 SEPARATING THE LANDFALLS OF THE ECMWF TO THE WEST OF THE OFFICIAL
 FORECAST FROM THE UKMET TO ITS EAST.  THE OFFICIAL FORECAST HAS
 BEEN SHIFTED SLIGHTLY WEST AND IS IN BEST AGREEMENT WITH THE FSU
 SUPERENSEMBLE...WHICH HAS PERFORMED WELL WITH THIS STORM. 
  
 THERE IS CONSIDERABLE SPREAD IN THE MODEL FORECASTS AFTER
 LANDFALL...AND IT IS POSSIBLE THAT THE REMNANTS OF IVAN WILL MOVE
 VERY SLOWLY OR STALL NEAR OR OVER THE APPALACHIANS IN 4 OR 5
 DAYS...WHICH WOULD PRODUCE A VERY SERIOUS FLOODING EVENT.
  
 FORECASTER FRANKLIN
  
 FORECAST POSITIONS AND MAX WINDS
  
 INITIAL      14/1500Z 23.4N  86.2W   120 KT
  12HR VT     15/0000Z 24.4N  86.9W   115 KT
  24HR VT     15/1200Z 26.3N  88.0W   115 KT
  36HR VT     16/0000Z 28.5N  88.5W   120 KT
  48HR VT     16/1200Z 30.5N  88.5W   110 KT...INLAND
  72HR VT     17/1200Z 34.0N  86.5W    40 KT...INLAND
  96HR VT     18/1200Z 36.0N  84.0W    20 KT...INLAND
 120HR VT     19/1200Z 36.5N  83.0W    20 KT...INLAND
  
  
 $$