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| #7716 (Received by flhurricane at: 11:00 AM 09.Sep.2004) 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 |
