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| #152597 (Received by flhurricane at: 4:52 PM 26.Sep.2007) TCDAT2 TROPICAL STORM KAREN DISCUSSION NUMBER 8 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL122007 500 PM EDT WED SEP 26 2007 KAREN'S INTENSIFICATION...AT LEAST FOR THE TIME BEING...HAS HALTED. THE INTERMITTENT EYE IS NO LONGER PRESENT AND DEEP CONVECTION IS MAINLY OCCURRING IN THE NORTHEASTERN SEMICIRCLE. SUBJECTIVE DVORAK ESTIMATES REMAIN AT 4.0 AND 3.5 FROM TAFB AND SAB...THOUGH THE ADVANCED DVORAK TECHNIQUE CONTINUES TO SUGGEST AN INTENSITY A BIT LOWER AT 50-55 KT. AN 1835Z AMSU CIMSS ESTIMATE ALSO GIVES A WIND OF 57 KT FOR KAREN. INITIAL INTENSITY IS KEPT AT 60 KT... THOUGH THIS MAY BE SOMEWHAT GENEROUS. KAREN IS MOVING AT 295/10 UNDER THE INFLUENCE OF A LOW- TO MID-LEVEL RIDGE TO ITS NORTH. A TROUGH IN THE UPPER TROPOSPHERE LOCATED WEST OF KAREN IS PREDICTED TO RETROGRADE WESTWARD AND INDUCE ENOUGH OF A WEAKNESS IN THE RIDGE TO TURN KAREN TOWARD THE NORTHWEST BETWEEN DAYS 3 AND 5. THE MODEL CONSENSUS HAS SHIFTED SLIGHTLY TO THE WEST IN THE 12Z RUNS. THE TRACK FORECAST IS CONSISTENT WITH THAT GUIDANCE EXCEPT TO PUT LESS WEIGHT ON THE GFS EARLY ON...DUE TO ITS TOO RAPID INITIAL MOTION...AND THE NOGAPS AT DAYS 4 AND 5...DUE TO ITS UNREALISTICALLY LARGE VORTEX AND NORTHWARD MOTION. AS IN MANY CASES...THE INTENSITY FORECAST IS NOT CLEAR CUT. KAREN REMAINS OVER WARM 28C WATER AND HAS ABUNDANT MOISTURE NEARBY BUT IS BEING IMPACTED BY MODERATE 15-20 KT WESTERLY SHEAR. THE SHEAR SHOULD CONTINUE AND PERHAPS BE ENHANCED DURING THE NEXT THREE DAYS. THE SHIPS AND LGM STATISTICAL GUIDANCE SUGGEST MODEST INTENSIFICATION DURING THE NEXT DAY...BUT THIS MAY BE OVERLY INFLUENCED BY THEIR PERSISTENCE PREDICTOR. THE GFDL AND HWRF DYNAMICAL GUIDANCE ARE LESS IMPRESSED WITH THE POTENTIAL FOR INTENSIFICATION. THE OFFICIAL INTENSITY FORECAST BRINGS KAREN TO A HURRICANE...BUT JUST BARELY...IN A DAY BEFORE A GRADUAL WEAKENING THEREAFTER. HOWEVER...IF THE SHEAR CONTINUES TO ADVERSELY IMPACT KAREN'S ABILITY TO MAINTAIN SYMMETRIC CONVECTION...THEN THE CYCLONE MAY BE SIGNIFICANTLY WEAKER THAN PREDICTED HERE. THE 12 FOOT SEAS RADII WERE ADJUSTED OUTWARD BASED UPON OBSERVATIONS FROM NOAA BUOY 41041. FORECAST POSITIONS AND MAX WINDS INITIAL 26/2100Z 12.4N 43.6W 60 KT 12HR VT 27/0600Z 13.2N 45.1W 60 KT 24HR VT 27/1800Z 14.6N 47.2W 65 KT 36HR VT 28/0600Z 15.9N 48.8W 65 KT 48HR VT 28/1800Z 17.0N 50.1W 60 KT 72HR VT 29/1800Z 19.0N 52.5W 55 KT 96HR VT 30/1800Z 21.0N 55.0W 55 KT 120HR VT 01/1800Z 23.0N 57.0W 55 KT $$ FORECASTER LANDSEA/PASCH |
