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| #372667 (Received by flhurricane at: 10:44 AM 31.Aug.2010) TCDAT3 TROPICAL STORM FIONA DISCUSSION NUMBER 4 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082010 1100 AM AST TUE AUG 31 2010 A 0929 UTC SSMIS MICROWAVE OVERPASS SHOWED CURVED BANDS OF CONVECTION LOOSELY WRAPPING AROUND THE CENTER. SINCE THAT TIME VISIBLE SATELLITE IMAGERY INDICATES THAT THE CONVECTIVE BANDS NEAR THE CENTER HAVE WEAKENED...WHILE NEW CONVECTION HAS DEVELOPED AROUND THE PERIPHERY OF THE CIRCULATION. THE INITIAL INTENSITY REMAINS 35 KT...BASED ON THE EARLIER SCATTEROMETER DATA. AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT IS SCHEDULED TO INVESTIGATE FIONA THIS AFTERNOON AND SHOULD PROVIDE A BETTER ASSESSMENT OF THE CURRENT STRUCTURE AND INTENSITY. THE INITIAL MOTION ESTIMATE IS 285/21 KT. THE CYCLONE IS FORECAST TO SLOW DOWN AND TURN NORTHWESTWARD DURING THE NEXT 24 HOURS AS IT NEARS THE WESTERN PORTION OF THE SUBTROPICAL RIDGE. THEREAFTER... FIONA IS EXPECTED TO TURN NORTH-NORTHWESTWARD...THEN NORTHWARD BETWEEN THE WESTERN SIDE OF THE RIDGE AND HURRICANE EARL TO THE NORTHWEST. THE TRACK GUIDANCE IS IN BETTER AGREEMENT ON THIS SCENARIO AND THE OFFICIAL FORECAST HAS BEEN ADJUSTED EASTWARD ALONG THE LEFT SIDE OF THE GUIDANCE ENVELOPE. LATE IN THE FORECAST PERIOD...FIONA SHOULD TURN NORTHEASTWARD AS DEEP SOUTHWESTERLY FLOW DEVELOPS OVER THE WESTERN ATLANTIC. THERE APPEARS TO BE A SMALL WINDOW OF OPPORTUNITY FOR FIONA TO STRENGTHEN DURING THE NEXT 12 TO 24 HOURS BEFORE AN UPPER-LEVEL RIDGE TO THE NORTHWEST OF FIONA STRENGTHENS...AND NORTHEASTERLY UPPER-LEVEL WINDS INCREASE. THE SHEAR IS FORECAST TO REMAIN MODERATE TO STRONG THROUGHOUT MOST OF THE FORECAST PERIOD AND NO ADDITIONAL STRENGTHENING IS PREDICTED. AN ALTERNATE SCENARIO...AS SHOWN BY THE GFS...IS THAT FIONA COULD WEAKEN AND POSSIBLY DISSIPATE IN A COUPLE OF DAYS DUE TO THE AFOREMENTIONED SHEAR. FORECAST POSITIONS AND MAX WINDS INITIAL 31/1500Z 15.9N 55.3W 35 KT 12HR VT 01/0000Z 16.9N 58.2W 40 KT 24HR VT 01/1200Z 18.7N 61.3W 45 KT 36HR VT 02/0000Z 21.1N 63.8W 45 KT 48HR VT 02/1200Z 23.4N 65.8W 45 KT 72HR VT 03/1200Z 27.7N 67.8W 45 KT 96HR VT 04/1200Z 31.0N 67.5W 45 KT 120HR VT 05/1200Z 34.0N 66.0W 45 KT $$ FORECASTER BROWN |
