ZCZC MIATCDAT4 ALL TTAA00 KNHC DDHHMM HURRICANE IVAN DISCUSSION NUMBER 23 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 11 PM EDT TUE SEP 07 2004 IVAN HAS CONTINUED TO STRENGTHEN DURING THE EVENING. THE LAST PASS OF AN AIR FORCE RESERVE HURRICANE HUNTER THROUGH THE EYE SHOWED A CENTRAL PRESSURE NEAR 950 MB AND MAXIMUM FLIGHT-LEVEL WINDS OF 129 KT AT 700 MB. THE INITIAL INTENSITY IS SET TO 115 KT BASED ON THE FLIGHT-LEVEL WINDS AND SATELLITE INTENSITY ESTIMATES OF 115 KT FROM ALL AGENCIES. IT SHOULD BE NOTED THAT THE SATELLITE SIGNATURE OF IVAN HAS IMPROVED SINCE 00Z AND THE INITIAL INTENSITY MAY BE CONSERVATIVE. THE NEXT AIRCRAFT IS SCHEDULED TO ARRIVE IN IVAN AROUND 06Z. THE INITIAL MOTION IS 280/15. IVAN REMAINS ON THE SOUTH SIDE OF A STRONG SUBTROPICAL RIDGE OVER THE WESTERN ATLANTIC. LARGE-SCALE MODELS FORECAST THIS RIDGE TO SLOWLY WEAKEN AS A MID/UPPER-LEVEL TROUGH APPROACHES IT FROM THE NORTHWEST AND AS AN UPPER-LEVEL LOW DEVELOPS TO THE EAST. WATER VAPOR IMAGERY ALSO INDICATES AN UPPER-LEVEL LOW OVER THE CENTRAL AND WESTERN CARIBBEAN...BUT THIS SEEEMS TO BE RETREATING WESTWARD AS FAST OR FASTER THAN THE HURRICANE. THE SYNOPTIC PATTERN SHOULD PRODUCE A WESTWARD TO WEST-NORTHWESTWARD MOTION FOR THE NEXT 72 HR OR SO...FOLLOWED BY A MORE NORTHWESTWARD MOTION AT A SLOWER FORWARD SPEED THEREAFTER. UNFORTUNATELY...MODEL GUIDANCE IS NOT VERY CONSISTENT FROM RUN TO RUN AT THE MOMENT. THE GFS MADE A HUGE SHIFT TO THE RIGHT...FROM PASSING WEST OF FLORIDA TO PASSING 200 NM EAST OF FLORIDA. THE GFDL ALSO SHIFTED TO THE RIGHT...BUT FROM A LEFT OUTLIER INTO THE MIDDLE OF THE GUIDANCE ENVELOPE. THE OFFICIAL FORECAST ALSO SHIFTS...A LITTLE TO THE SOUTH EARLY IN THE FORECAST TO ALLOW FOR THE CURRENT POSITION AND MOTION AND A LITTLE TO THE RIGHT LATER IN THE FORECAST PERIOD. IT IS IN BEST AGREEMENT WITH THE NOGAPS. UPPER-LEVEL WINDS ARE FORECAST TO BE GENERALLY FAVORABLE FOR DEVELOPMENT THROUGH THE FORECAST PERIOD...SO THE INTENSITY OF IVAN WILL BE MAINLY CONTROLLED BY CONCENTRIC EYEWALL CYCLES...CHANGES IN SEA SURFACE TEMPERATURE...AND LAND INTERACTION. AN SSM/I OVERPASS AT 0105Z SHOWED AN OUTER EYEWALL STARTING TO FORM...WHICH SUGGEST THE CURRENT INTENSIFICATION CYCLE WILL STOP IN 6-12 HR. HOWEVER... BY THAT TIME IVAN MAY BE STRONGER THAN CURRENTLY FORECAST. THE HURRICANE WILL PASS OVER SOME SLIGHTLY COOLER SEA SURFACE TEMPERATURES THROUGH 48 HR...THEN REACH WARMER WATER NORTHWEST OF JAMAICA AFTER 72 HR. REGARDLESS OF THE EXACT UPS AND DOWNS IN THE INTENSITY...IVAN IS EXPECTED TO REMAIN A STRONG HURRICANE THROUGH THE FORECAST PERIOD...MOST LIKELY CATEGORY 4 BUT POSSIBLY REACHING CATEGORY 5 AT SOME POINTS. HURRICANE WARNINGS HAVE BEEN ISSUED FOR ARUBA...BONAIRE...AND CURACAO...AS ANY MOTION SOUTH OF THE FORECAST TRACK COULD BRING HURRICANE FORCE WINDS NEAR OR OVER THOSE ISLANDS. FORECASTER BEVEN FORECAST POSITIONS AND MAX WINDS INITIAL 08/0300Z 12.1N 63.3W 115 KT 12HR VT 08/1200Z 12.8N 65.7W 125 KT 24HR VT 09/0000Z 13.8N 68.8W 130 KT 36HR VT 09/1200Z 14.9N 71.6W 130 KT 48HR VT 10/0000Z 16.3N 74.2W 130 KT 72HR VT 11/0000Z 19.0N 78.5W 120 KT 96HR VT 12/0000Z 21.0N 81.0W 130 KT 120HR VT 13/0000Z 24.0N 83.0W 120 KT $$ NNNN
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Page last modified: Wednesday, 08-Sep-2004 03:22:53 UTC