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| #152742 (Received by flhurricane at: 4:37 PM 27.Sep.2007) TCDAT2 TROPICAL STORM KAREN DISCUSSION NUMBER 12 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL122007 500 PM EDT THU SEP 27 2007 PERSISTENTLY STRONG SOUTHWESTERLY SHEAR CONTINUES TO AFFECT THE TROPICAL CYCLONE...DISPLACING THE DEEP CONVECTION FROM THE CIRCULATION CENTER. ALTHOUGH DVORAK SATELLITE INTENSITY ESTIMATES FROM TAFB AND SAB HAVE DECREASED TO 45 KT...SOME RECENT DEEP CONVECTIVE BURSTS NEAR THE CENTER SUGGEST A SLIGHTLY HIGHER INTENSITY. THEREFORE...THE INITIAL WIND SPEED IS SET TO 50 KT. THE INTENSITY FORECAST IS RELATIVELY STRAIGHTFORWARD THROUGH DAY 5...INDICATING GRADUAL WEAKENING. HOWEVER...LARGE-SCALE DYNAMICAL MODELS...SHIPS...AND THE LGEM ARE NOW SUGGESTING THAT THE SHEAR WILL BEGIN TO WEAKEN AROUND THE 96 TO 120 HR PERIOD WHEN THE TROPICAL CYCLONE REACHES THE UPPER TROUGH AXIS. CONSEQUENTLY... SLIGHT INTENSIFICATION IN THE LATTER PART OF THE PERIOD IS POSSIBLE...ALBEIT NOT INDICATED IN THE OFFICIAL FORECAST AT THIS TIME. KAREN IS MOVING AT 305/11...WITH THIS GENERAL MOTION CONTINUING DURING THE NEXT 2 DAYS OR SO AS KAREN PROPAGATES WITHIN THE DEEP-LAYERED FLOW ASSOCIATED WITH THE SUBTROPICAL RIDGE TO THE NORTH. THROUGH THE REMAINING PORTION OF THE FORECAST...THE DYNAMICAL MODELS ARE AGREEING IN BUILDING THE MID- LEVEL RIDGE MORE TOWARD THE NORTHWEST OF THE CYCLONE CAUSING KAREN TO TURN MORE WEST-NORTHWESTWARD. THE OFFICIAL FORECAST IS CLOSE TO THE PREVIOUS PACKAGE AND IS BASED ON A CONSENSUS OF THE MODELS. FORECAST POSITIONS AND MAX WINDS INITIAL 27/2100Z 14.3N 48.5W 50 KT 12HR VT 28/0600Z 15.5N 49.8W 45 KT 24HR VT 28/1800Z 16.8N 51.5W 45 KT 36HR VT 29/0600Z 17.8N 52.8W 45 KT 48HR VT 29/1800Z 18.7N 54.0W 45 KT 72HR VT 30/1800Z 20.5N 55.5W 40 KT 96HR VT 01/1800Z 22.5N 56.5W 40 KT 120HR VT 02/1800Z 24.0N 58.5W 40 KT $$ FORECASTER ROBERTS/AVILA |
