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#109662 (Received by flhurricane at: 5:14 AM 09.Sep.2006) TCDAT1 TROPICAL STORM FLORENCE DISCUSSION NUMBER 23 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL062006 500 AM EDT SAT SEP 09 2006 AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT REACHED THE CENTER OF FLORENCE ABOUT 04Z...WITH A SECOND FIX ABOUT 0630Z. THE AIRCRAFT MEASURED MINIMUM PRESSURES OF 998 AND 993 MB ON THE TWO FIXES... WITH MAXIMUM 850 MB FLIGHT-LEVEL WINDS OF 61 KT ABOUT 50 N MI NORTHEAST OF THE CENTER. SATELLITE INTENSITY ESTIMATES ARE 65 KT FROM SAB AND AFWA...AND 55 KT FROM TAFB. THE INITIAL INTENSITY REMAINS 55 KT FOR THIS ADVISORY. IT SHOULD BE NOTED THAT THE AIRCRAFT AND RECENT AMSR-E DATA SHOW THAT WHILE THE CONVECTION IS STRONG...IT IS CURRENTLY CONFINED TO THE NORTHERN QUADRANT. THE AIRCRAFT FOUND THE CENTER SOUTH OF THE PREVIOUS FORECAST TRACK...AND A REVIEW OF EARLIER SATELLITE DATA SUGGESTS THAT FLORENCE HAS BEEN MOVING WEST-NORTHWESTWARD FOR THE PAST 12 HR OR SO. THE INITIAL MOTION IS 300/12. OTHER THAN THIS...THERE IS NO CHANGE IN THE FORECAST PHILOSOPHY. WATER VAPOR IMAGERY SHOWS THAT FLORENCE IS APPROACHING THE WESTERN END OF A DEEP-LAYER RIDGE... WITH AN UPPER-LEVEL LOW SOUTHWEST OF THE STORM NEAR 21N71W AND A MID/UPPER-LEVEL SHORTWAVE TROUGH APPROACHING THE EAST COAST OF THE UNITED STATES. THIS COMBINATION SHOULD TURN FLORENCE NORTHWARD DURING THE NEXT 12-36 HR...WITH THE STORM RECURVING NORTHEASTWARD IN DEEP-LAYER SOUTHWESTERLY FLOW THEREAFTER. ALL MODEL GUIDANCE AGREES ON THE RECURVATURE...WITH LBAR CALLING FOR THE FARTHEST WEST RECURVATURE AT 68W. THERE REMAINS SOME SPREAD IN THE MODEL GUIDANCE AFTER RECURVATURE. THE NOGAPS...GFDN...GFDL...AND ECMWF BRING THE CENTER OVER SOUTHEASTERN NEWFOUNDLAND...WHILE THE REMAINDER OF THE GUIDANCE KEEPS IT SOUTHEAST OF THE ISLAND. THE NEW FORECAST TRACK IS MOVED WESTWARD FOR THE FIRST 48 HR DUE TO THE CURRENT POSITION AND MOTION...AND NOW CALLS FOR FLORENCE TO PASS VERY NEAR BERMUDA IN 48-72 HR. THE LATTER PART OF THE FORECAST IS SIMILAR TO THE PREVIOUS PACKAGE. OVERALL...THE NEW FORECAST TRACK IS JUST TO THE LEFT OF THE MODEL CONSENSUS. ANALYSES FROM CIMSS AT THE UNIVERSITY OF WISCONSIN INDICATE THAT THE VERTICAL SHEAR HAS DECREASED TO ABOUT 10 KT. FLORENCE HAS ABOUT A 48-60 HR WINDOW IN WHICH TO INTENSIFY BEFORE ENCOUNTERING STRONG SHEAR IN THE WESTERLIES. THE SHIPS AND FSU SUPERENSEMBLE BOTH FORECAST A PEAK INTENSITY OF 100-105 KT IN ABOUT 60 HR...WHILE THE GFDL CALLS FOR A PEAK INTENSITY OF 87 KT. THE INTENSITY FORECAST IS AN UPDATE OF THE PREVIOUS PACKAGE...CALLING FOR A PEAK INTENSITY OF 90 KT IN ABOUT 48 HR. AFTER FLORENCE ENTERS THE WESTERLIES... INCREASING VERTICAL SHEAR AND COLD AIR INTRUSION SHOULD CAUSE WEAKENING AND EXTRATROPICAL TRANSITION BY 120 HR. HOWEVER... FLORENCE SHOULD REMAIN A LARGE AND VIGOROUS CYCLONE THROUGH THE TRANSITION PROCESS. FORECAST POSITIONS AND MAX WINDS INITIAL 09/0900Z 24.1N 62.8W 55 KT 12HR VT 09/1800Z 25.1N 64.3W 65 KT 24HR VT 10/0600Z 26.7N 65.4W 75 KT 36HR VT 10/1800Z 28.6N 65.9W 85 KT 48HR VT 11/0600Z 30.6N 65.8W 90 KT 72HR VT 12/0600Z 36.0N 63.0W 85 KT 96HR VT 13/0600Z 43.0N 56.0W 70 KT...BECOMING EXTRATROPICAL 120HR VT 14/0600Z 49.0N 46.0W 60 KT...EXTRATROPICAL $$ FORECASTER BEVEN |