ZCZC MIATCDAT3 ALL TTAA00 KNHC DDHHMM HURRICANE ISABEL DISCUSSION NUMBER 10 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 11 AM EDT MON SEP 08 2003 ISABEL HAS CONTINUED TO RAPIDLY INTENSIFY. THE INITIAL INTENSITY IS INCREASED TO 100 KT BASED ON SATELLITE INTENSITY ESTIMATES OF 115 KT FROM TAFB AND AFWA...102 KT FROM SAB...AND 102 KT/T5.5 3-HOUR OBJECTIVE DVORAK INTENSITY ESTIMATES. THE 100 KT INITIAL INTENSITY IS ALSO CONSISTENT WITH THE LATEST AMSU INTENSITY ESTIMATES OF 100 KT AND 960 MB. OUTFLOW REMAINS QUITE IMPRESSIVE AND CONTINUES TO IMPROVE AND THE EYE DIAMETER HAS DECREASED DOWN TO 25 NMI. THE INITIAL MOTION ESTIMATE IS 290/12. IS APPEARS THAT ISABEL MAY BE MAKING THE MORE WESTWARD TURN THAT THE GLOBAL MODELS HAVE BEEN INDICATING. THE NHC MODEL GUIDANCE IS EVEN MORE TIGHTLY PACKED AND IN GOOD AGREEMENT ON ISABEL MOVING WEST-NORTHWESTWARD FOR THE NEXT 36 HOURS...AND THEN TURNING MORE WESTWARD AFTER THAT. THIS IS QUITE REASONABLE GIVEN THE STRENGTH AND EAST-WEST ORIENTATION OF THE SUBTROPICAL RIDGE LOCATED ALONG 32N LATITUDE. A DISCONCERTING PART OF THE MODEL GUIDANCE IS THE GFS AND NOGAPS MODELS CONTINUING TO INSIST THAT ISABEL WILL MAKE A DIP SOUTH-OF-WEST AFTER 72 HOURS. THEY BRING ISABEL DANGEROUSLY CLOSE TO THE NORTHERN LEEWARD ISLANDS BY 120 HOURS. THE GFS AND NOGAPS HAD A LEFT OF TRACK BIAS WITH FABIAN LAST WEEK...SO I PREFER TO WAIT ANOTHER 24 HOURS OR SO TO SEE IF THIS SAME BIAS DEVELOPS. HOWEVER...THIS SCENARIO CAN NOT BE COMPLETELY RULED OUT GIVEN THE DEEP MID-/UPPER-LEVEL TROUGH NORTHWEST OF AFRICA THAT HAS BEEN DIGGING SOUTHWESTWARD. THAT COULD CREATE ENOUGH LOW-LEVEL RIDGING FROM THE NORTHEAST TO NUDGE ISABEL A LITTLE SOUTH OF DUE WEST...SIMILAR TO THE GFS-NOGAPS SCENARIO. ISABEL IS ABOUT 18-24 HOURS INTO A RAPID INTENSIFICATION CYCLE...SO THIS TREND IS FORECAST TO CONTINUE FOR ANOTHER 12 HOURS OR SO. AFTER REACHING CATEGORY 4 INTENSITY...INNER-CORE CONVECTION AND EYEWALL DYNAMICS WILL DICTATE ANY INTENSITY CHANGES. HOWEVER...THE INTENSITY FORECAST COULD EASILY BE TOO LOW GIVEN THE CURRENT AND FORECAST OUTFLOW PATTERN THAT WILL EVOLVE OVER THE NEXT 48 HOURS. FORECASTER STEWART FORECAST POSITIONS AND MAX WINDS INITIAL 08/1500Z 17.2N 42.6W 100 KT 12HR VT 09/0000Z 17.9N 44.4W 115 KT 24HR VT 09/1200Z 18.6N 46.8W 120 KT 36HR VT 10/0000Z 19.2N 49.1W 120 KT 48HR VT 10/1200Z 19.4N 51.1W 120 KT 72HR VT 11/1200Z 19.5N 55.0W 120 KT 96HR VT 12/1200Z 19.5N 58.5W 120 KT 120HR VT 13/1200Z 20.0N 62.5W 120 KT NNNN
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Page last modified: Monday, 07-Feb-2005 16:49:58 UTC