183 
 WTNT44 KNHC 070305
 TCDAT4
 HURRICANE IVAN DISCUSSION NUMBER  19
 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
 11 PM EDT MON SEP 06 2004
  
 AN EVALUATION OF THE DATA FROM THE HURRICANE HUNTERS SUGGESTS THAT
 IVAN HAS MAINTAINED ITS INTENSITY OVER THE LAST FEW HOURS.
 DROPSONDES THROUGHOUT THE MISSION HAVE SHOWN A MODEST DROP IN
 PRESSURE FROM 969 MB TO 963 MB.  THE MAXIMUM FLIGHT LEVEL WIND
 MEASURED WAS 106 KT...CORRESPONDING TO A SURFACE WIND OF 85 KT.
 SATELLITE INTENSITY ESTIMATES RANGE FROM 65 KT TO 90 KT...THE
 INITIAL INTENSITY IS KEPT AT 90 KT.
 
 THE INITIAL MOTION IS 275/18.  RECONNAISSANCE AIRCRAFT PROVIDED A
 FIX TO THE SOUTH OF THE PREVIOUS FORECAST TRACK.  IVAN IS EXPECTED
 TO RESUME A WEST-NORTHWEST COURSE SOON...AS UNIVERSALLY SUGGESTED
 BY THE MODEL GUIDANCE.  DUE IN PART TO A MORE SOUTHERLY INITIAL
 POSITION...THE FORECAST TRACK IS TO THE LEFT OF THE PREVIOUS ONE. 
 THERE IS A DIFFERENCE OF OPINION IN THE DYNAMICAL MODELS AT 96 AND
 120 HOURS.  THE GFS...UKMET...AND THE FSU SUPERENSEMBLE BRING IVAN
 WELL SOUTH OF CUBA TOWARD THE YUCATAN PENNINSULA.  NOGAPS AND THE
 GFDL BRING IVAN MUCH CLOSER TO THE SOUTHERN COAST OF CUBA.  THE
 OFFICIAL FORECAST SPLITS THE DIFFERENCE AND IS LINE WITH THE
 CLOSELY PACKED MODEL CONSENSUS POINTS.         
 
 A NOAA JET IN IVAN THIS EVENING HAS FOUND THE EXISTENCE OF A SAHARAN
 AIR LAYER IN THE NORTHERN QUADRANTS OF THE STORM.  THIS MAY HELP
 EXPLAIN THE WEAKENING OF IVAN THROUGHOUT THE DAY TODAY.  IVAN IS
 EXPECTED TO GRADUALLY INTENSIFY AS IT PROCEEDS TO THE WEST
 THROUGHOUT THE FORECAST PERIOD.  SINCE THE NEW FORECAST KEEPS IVAN
 AWAY FROM ANY MAJOR LAND AREAS...THE INTENSITY OF IVAN IN THE LATER
 PERIODS ARE MAINTAINED.  
  
 FORECASTER LAWRENCE/HENNON
  
 FORECAST POSITIONS AND MAX WINDS
  
 INITIAL      07/0300Z 11.2N  57.2W    90 KT
  12HR VT     07/1200Z 11.8N  59.8W    95 KT
  24HR VT     08/0000Z 12.7N  62.9W   100 KT
  36HR VT     08/1200Z 13.7N  66.1W   105 KT
  48HR VT     09/0000Z 14.7N  69.1W   110 KT
  72HR VT     10/0000Z 17.2N  74.3W   115 KT
  96HR VT     11/0000Z 19.5N  78.7W   115 KT
 120HR VT     12/0000Z 21.5N  82.4W   115 KT
  
  
 $$