326 
 WTNT44 KNHC 091452
 TCDAT4
 HURRICANE IVAN DISCUSSION NUMBER  29
 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
 11 AM EDT THU SEP 09 2004
  
 THE LAST RECONNAISSANCE FIX WAS EARLIER THIS MORNING ABOUT 1141Z.
 FLIGHT LEVEL...700 MB...WINDS WERE 156 KNOTS WITH AN EXTRAPOLATED
 PRESSURE OF 917 MB AND 921 MB MEASURED BY A DROP. IVAN HAS AN
 OUTSTANDING SATELLITE PRESENTATION...HOWEVER...THE RING OF
 CONVECTION SURROUNDING THE EYE HAS WEAKENED A LITTLE BIT. INITIAL
 INTENSITY REMAINS AT 140 KNOTS. HURRICANES NORMALLY DO NOT MAINTAIN
 SUCH PEAK INTENSITY FOR A LONG TIME AND MOST LIKELY THERE WILL WE
 SOME SLIGHT WEAKENING. THE HURRICANE WILL PROBABLY FLUCTUATE
 BETWEEN CAT 4 AND 5 UNTIL IT REACHES CUBA.  THEREAFTER..THE EFFECTS
 OF LAND...INCREASING SHEAR AND LOWER OCEAN HEAT CONTENT WILL CAUSE
 WEAKENING.
 
 IVAN IS MOVING TOWARD THE WEST-NORTHWEST AT 13 KNOTS. THIS GENERAL
 MOTION WITH A GRADUAL DECREASE IN FORWARD SPEED IS EXPECTED DURING
 THE NEXT 3 DAYS. THERE HIGH CONFIDENCE IN THIS PORTION OF THE
 FORECAST BECAUSE THE HURRICANE WILL BE STEERED BY THE FLOW
 SURROUNDING A WELL-ESTABLISHED SUBTROPICAL RIDGE. ALL MODELS ARE
 HIGHLY CLUSTERED DURING THIS PERIOD...BRINGING THE HURRICANE
 BETWEEN CUBA AND THE CAYMAN ISLANDS. THEREAFTER...THE FORECAST
 TRACK BECOMES HIGHLY UNCERTAIN. STEERING CURRENTS ARE FORECAST TO
 COLLAPSE AND CONSEQUENTLY...THE HURRICANE IS EXPECTED TO SLOW DOWN
 AS IT CROSSES CUBA.  A RIDGE OVER THE BAHAMAS A LITTLE STRONGER
 THAN ANTICIPATED...WILL BRING THE HURRICANE TOWARD THE EASTERN GULF
 OF MEXICO AS INDICATED BY THE UK...CANADIAN AND NOGAPS GLOBAL
 MODELS. A WEAKER RIDGE THAN ANTICIPATED COULD RESULT ON A MORE
 NORTHWARD TRACK OVER THE BAHAMAS AND NEARBY THE EAST COAST OF
 FLORIDA AS INDICATED BY THE GFS. THE 4-5 DAY OFFICIAL
 FORECAST...WHICH IS HIGHLY UNCERTAIN...CALLS FOR A SOLUTION IN
 BETWEEN...BRINGING THE HURRICANE OVER WEST/CENTRAL CUBA INTO THE
 SOUTHEASTERN GULF OF MEXICO AND THEN FLORIDA. 
  
 FORECASTER AVILA
 
 FORECAST POSITIONS AND MAX WINDS
  
 INITIAL      09/1500Z 14.5N  71.4W   140 KT
  12HR VT     10/0000Z 15.3N  73.3W   140 KT
  24HR VT     10/1200Z 17.0N  75.2W   135 KT
  36HR VT     11/0000Z 18.5N  77.3W   135 KT
  48HR VT     11/1200Z 19.5N  79.0W   135 KT
  72HR VT     12/1200Z 21.0N  80.5W   130 KT
  96HR VT     13/1200Z 24.0N  82.0W   115 KT
 120HR VT     14/1200Z 28.5N  82.0W    85 KT INLAND
  
  
 $$