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| #7343 (Received by flhurricane at: 10:46 PM 03.Sep.2004) TCDAT4 TROPICAL STORM IVAN DISCUSSION NUMBER 6 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 11 PM EDT FRI SEP 03 2004 SATELLITE DVORAK INTENSITY ESTIMATES REMAIN AT 45 KT FROM TAFB AND SAB. A RECENT QUIKSCAT PASS HAD RAIN-FLAGGED 55 KT SURFACE WINDS WELL SOUTH OF THE CENTER AND SO DID A PASS FROM EARLY FRIDAY MORNING. SINCE THE DVORAK ESTIMATES HAVE BEEN THE SAME ALL DAY FROM SAB...THE OFFICIAL INTENSITY WILL STAY THE SAME AS THE PREVIOUS ADVISORY...45 KT. THE SHIPS MODEL BRINGS THE WIND SPEED TO 96 KT IN 120 HOURS UNDER DECREASING VERTICAL WIND SHEAR AND OF COURSE WARM SSTS OVER THE TROPICAL ATLANTIC. THE GFDL IS MUCH MORE AGGRESSIVE BUT...AS IS USUALLY THE CASE...THE OFFICIAL FORECAST FOLLOWS THE SHIPS MODEL AND IS SIMILAR TO THE PREVIOUS ADVISORY. THE INITIAL POSITION IS A LITTLE NORTH OF THE GOES 12 INFRARED FIXES BASED ON AN ANALYSIS OF THE 2228Z QUIKSCAT AMBIGUITY WIND FIELD. THIS GIVES AN INITIAL MOTION ESTIMATE OF 265/15. THE GLOBAL MODELS ALL SHOW THE SUBTROPICAL RIDGE HOLDING TO THE NORTH OF IVAN AND ALL SHOW A WEST-NORTHWEST TRACK EXCEPT BECOMING A LITTLE MORE NORTHWESTWARD AFTER 96 HOURS. THE GFS IS THE LEFT-MOST TRACK AND THE NOGAPS AND GFDL EMBEDDED IN THE NOGAPS ARE THE RIGHT-MOST TRACKS. THE OFFICIAL TRACK FORECAST IS ADJUSTED TO THE RIGHT OF THE PREVIOUS FORECAST BUT IS STILL LEFT OF A CONSENSUS OF THE GLOBAL MODELS. IN ANY CASE IVAN SHOULD MOVE SOMEWHERE ACROSS THE LESSER ANTILLES IN 4 TO 5 DAYS. FORECASTER LAWRENCE FORECAST POSITIONS AND MAX WINDS INITIAL 04/0300Z 9.1N 35.8W 45 KT 12HR VT 04/1200Z 9.2N 38.0W 55 KT 24HR VT 05/0000Z 9.4N 41.0W 60 KT 36HR VT 05/1200Z 10.2N 44.0W 65 KT 48HR VT 06/0000Z 11.0N 47.0W 75 KT 72HR VT 07/0000Z 12.5N 53.5W 85 KT 96HR VT 08/0000Z 14.5N 59.5W 90 KT 120HR VT 09/0000Z 16.5N 64.0W 95 KT |
