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| #7882 (Received by flhurricane at: 10:41 PM 10.Sep.2004) TCDAT4 HURRICANE IVAN DISCUSSION NUMBER 35 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 11 PM EDT FRI SEP 10 2004 DURING THE AFTERNOON...THE AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT MONITORING IVAN REPORTED A PRESSURE FALL FROM 940 MB TO 926 MB IN ABOUT 5 HOURS. SINCE THEN...THE HURRICANE HAS CONTINUED TO BECOME BETTER ORGANIZED...WITH SATELLITE INTENSITY ESTIMATES IN THE 127-140 KT RANGE. ONE CONUNDRUM IS THAT THE AIRCRAFT COULD NOT FIND A FLIGHT-LEVEL WIND OF HIGHER THAN 123 KT...WHICH WOULD NOT SUPPORT CATEGORY 4 INTENSITY. THE INITIAL INTENSITY IS INCREASED TO 135 KT BASED ON THE SATELLITE SIGNATURE...THE ESTIMATED PRESSURE...AND THE PREMISE THAT THE WINDS ARE CATCHING UP WITH THE PRESSURE. THE INITIAL MOTION HAS BEEN WOBBLING AROUND 300/9. THERE IS NO CHANGE IN THE TRACK FORECAST PHILOSOPHY. IVAN SHOULD MOVING WEST-NORTHWESTWARD AROUND A WEAKENING SUBTROPICAL RIDGE...THEN GRADUALLY TURN TOWARD THE NORTHWEST OR NORTH AFTER 48 HR AS THE RIDGE STRENGTHENS IN THE ATLANTIC AND A TROUGH DROPS SOUTHWARD OVER THE NORTHERN GULF COAST. ALL GUIDANCE AGREES WITH THE BASIC SCNEARIO...WITH THE GFS CALLING FOR AN EARLIER TURN AND LANDFALL ON THE SOUTHWEST FLORIDA PENINSULA AND THE NOGAPS CALLING FOR A MORE NORWARD MOTION TO THE CENTRAL FLORIDA PANHANDLE. THE OTHER DYNAMIC MODELS ARE IN BETWEEN...AS IS THE FORECAST TRACK...WHICH IS BASICALLY AN UPDATE OF THE PREVIOUS TRACK AND TAKE IVAN TO THE FLORIDA BIG BEND REGION IN 96 HR. A SLIGHT CHANGE TO THE RIGHT OF THE TRACK COULD BRING IVAN INLAND ANYWHERE ALONG THE WEST COAST OF FLORIDA. IVAN HAS WELL-DEFINED CONCENTRIC EYEWALLS SEEN IN AIRCRAFT... MICROWAVE SATELLITE...AND EARLIER JAMAICAN RADAR DATA. THIS SUGGESTS THAT THE CURRENT INTENSIFICATION HAS MAYBE 6-12 HR TO RUN...AND THAT IS NOT ALLOWING FOR ANY LAND EFFECTS AS THE SYSTEM CROSSES JAMAICA SHORTLY. AS THE SYSTEM CROSSES THE NORTHWESTERN CARIBBEAN DURING THE NEXT 24-36 HR...THE UPPER-LEVEL WINDS SHOULD REMAIN FAVORABLE ENOUGH TO ALLOW IVAN TO REGAIN CATEGORY 5 STATUS AT SOME POINT DURING ITS FLUCTUATIONS DURING THE EYEWALL CYCLES. AFTER 48 HR...A GRADUAL INCREASE IN SHEAR AND INTERACTION WITH LAND SHOULD CAUSE A GRADUAL WEAKENING. HOWEVER...IVAN SHOULD REMAIN A MAJOR HURRICANE UNTIL LANDFALL IN FLORIDA. FORECASTER BEVEN FORECAST POSITIONS AND MAX WINDS INITIAL 11/0300Z 17.5N 76.9W 135 KT 12HR VT 11/1200Z 18.3N 77.9W 135 KT 24HR VT 12/0000Z 19.3N 79.1W 140 KT 36HR VT 12/1200Z 20.4N 80.4W 140 KT 48HR VT 13/0000Z 21.8N 81.5W 140 KT 72HR VT 14/0000Z 25.0N 83.0W 115 KT 96HR VT 15/0000Z 30.0N 83.5W 100 KT...INLAND 120HR VT 16/0000Z 35.5N 83.0W 30 KT...INLAND |
