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| #636382 (Received by flhurricane at: 10:38 PM 04.Oct.2013) TCDAT2 TROPICAL STORM KAREN DISCUSSION NUMBER 8 NWS NATIONAL HURRICANE CENTER MIAMI FL AL122013 1000 PM CDT FRI OCT 04 2013 KAREN HAS BEEN DECAPITATED BY STRONG SOUTHWESTERLY SHEAR AND NOW CONSISTS OF A VERY TIGHT SWIRL OF LOW CLOUDS WITH SOME LINEAR CONVECTION TO THE EAST OF THE CENTER. DATA FROM RECONNAISSANCE PLANES INDICATE THAT THERE IS A WELL-DEFINED CIRCULATION...BUT THE WINDS ARE GRADUALLY DECREASING. ON THIS BASIS...THE INITIAL INTENSITY HAS BEEN LOWERED TO 40 KNOTS IN THIS ADVISORY. TROPICAL STORMS RARELY RECOVER AFTER BEING STRONGLY DAMAGED BY SHEAR...ESPECIALLY IF THE ENVIRONMENT IS AS DRY AS IT IS OVER THE WESTERN GULF OF MEXICO. GIVEN THE VIGOROUS CIRCULATION...AND THE LOW PRESSURE...THE NHC FORECAST KEEPS KAREN WITH 40 KNOTS THROUGH 24 HOURS. AFTER THAT...WHEN THE CYCLONE TURNS TO THE NORTHEAST... THERE IS A SMALL WINDOW OF OPPORTUNITY FOR KAREN TO STRENGTHEN SLIGHTLY IF THE SHEAR RELAXES AS INDICATED BY THE SHIPS MODEL. AS PREVIOUSLY INDICATED...AN ALTERNATIVE SCENARIO IS THAT KAREN REMAINS DECOUPLED FROM THE DEEP CONVECTION AND WEAKENS AT A FASTER PACE. THE LATTER SCENARIO IS BECOMING MORE REALISTIC GIVEN THE CURRENT ORGANIZATION OF THE CYCLONE. FOR NOW...THE NHC FORECAST OPTED TO FOLLOW THE SLIGHT STRENGTHENING INDICATED BY THE INTENSITY CONSENSUS. KAREN IS EXPECTED TO BECOME EXTRATROPICAL IN 72 HOURS AND THEN ABSORBED BY A FRONTAL SYSTEM. KAREN HESITATED A FEW HOURS AGO...BUT NOW IT HAS BEGUN TO MOVE TOWARD THE NORTH-NORTHWEST OR 340 DEGREES AT ABOUT 6 KNOTS. KAREN IS ABOUT TO BE INFLUENCED BY THE FLOW AHEAD OF AN APPROACHING MID-LEVEL TROUGH AND MOST LIKELY THE CYCLONE WILL MAKE A SHARP TURN TO THE NORTHEAST ON SATURDAY WITH AN INCREASE IN FORWARD SPEED. THERE IS CONFIDENCE IN THE TRACK FORECAST SINCE MOST OF THE MODELS AGREE WITH THIS TURN TO THE NORTHEAST ON SATURDAY. FORECAST POSITIONS AND MAX WINDS INIT 05/0300Z 26.4N 90.5W 40 KT 45 MPH 12H 05/1200Z 27.1N 90.6W 40 KT 45 MPH 24H 06/0000Z 28.1N 90.0W 40 KT 45 MPH 36H 06/1200Z 29.0N 88.7W 45 KT 50 MPH 48H 07/0000Z 30.5N 86.5W 45 KT 50 MPH 72H 08/0000Z 34.5N 80.5W 25 KT 30 MPH...POST-TROP/EXTRATROP 96H 09/0000Z...ABSORBED $$ FORECASTER AVILA |
