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| #373222 (Received by flhurricane at: 4:44 PM 02.Sep.2010) TCDAT3 TROPICAL STORM FIONA DISCUSSION NUMBER 13 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082010 500 PM AST THU SEP 02 2010 THERE HAS BEEN LITTLE CHANGE WITH FIONA DURING THE DAY. THE STORM CONTINUES THE PATTERN OBSERVED DURING THE LAST DAY OR SO OF BURSTS OF CONVECTION FORMING NEAR THE CENTER...THEN SHEARING AWAY. AN ASCAT PASS FROM LATE THIS MORNING SHOWED MAXIMUM WINDS OF ABOUT 40 KT. GIVEN THE WELL-DOCUMENTED LOW BIAS OF THAT INSTRUMENT...45 KT SEEMS LIKE A REASONABLE INITIAL WIND SPEED. THE INTENSITY FORECAST IS DIFFICULT BECAUSE IT SEEMS LIKE FIONA HAS BEEN WITHSTANDING THE SHEAR BETTER THAN MOST TROPICAL CYCLONES. THE LATEST INTENSITY GUIDANCE DOES NOT WEAKEN THE STORM AS QUICKLY AS EARLIER...BUT IS ACTUALLY PRETTY CLOSE TO THE PREVIOUS FORECAST. THUS NO CHANGES ARE MADE TO THE LAST NHC FORECAST. AFTER 72 HOURS...ALL OF THE GLOBAL MODELS SHOW THE TROPICAL CYCLONE SHEARING OUT AS IT MOVES NORTHEASTWARD. FIONA HAS TURNED A LITTLE MORE AND IS NOW MOVING 335/15. THERE IS NO CHANGE IN SYNOPTIC REASONING WITH THE CYCLONE MOVING AROUND A SUBTROPICAL ANTICYCLONE. THE STORM SHOULD TURN TOWARD THE NORTH... THEN NORTHEAST AS IT STARTS TO MOVE INTO THE MID-LATITUDES. THE MODELS ARE GENERALLY SLOWER THAN THE PREVIOUS CYCLE...BUT SINCE THE CYCLONE CONTINUES SPEEDING ALONG...THE NHC FORECAST WILL STAY ON THE FASTER SIDE OF THE GUIDANCE ENVELOPE...WITH LITTLE CHANGE TO THE TRACK. THERE IS REASONABLE AGREEMENT THAT FIONA WILL BE CLOSE TO BERMUDA IN 36-48 HOURS. FORECAST POSITIONS AND MAX WINDS INITIAL 02/2100Z 25.6N 66.4W 45 KT 12HR VT 03/0600Z 27.5N 66.8W 45 KT 24HR VT 03/1800Z 29.7N 66.4W 45 KT 36HR VT 04/0600Z 31.7N 65.4W 40 KT 48HR VT 04/1800Z 33.7N 64.1W 35 KT 72HR VT 05/1800Z 38.0N 61.0W 25 KT...DISSIPATING 96HR VT 06/1800Z...DISSIPATED $$ FORECASTER BLAKE/BROWN |
