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| #152667 (Received by flhurricane at: 4:43 AM 27.Sep.2007) TCDAT2 TROPICAL STORM KAREN DISCUSSION NUMBER 10 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL122007 500 AM EDT THU SEP 27 2007 THE STRONG SOUTHWESTERLY SHEAR HAS TAKEN A TOLL ON KAREN THIS MORNING. RECENT TRMM AND AMSU-B MICROWAVE PASSES SUGGEST THAT THE LOW-LEVEL CIRCULATION CENTER HAS CONTINUED TO BECOME DECOUPLED FROM THE MID- AND UPPER-LEVELS. CONVENTIONAL SATELLITE IMAGERY INDICATE AN ELONGATED AREA OF DEEP CONVECTION ABOUT 60 N MI NORTHEAST OF THE CENTER...EXTENDING NORTHEASTWARD FOR A COUPLE OF HUNDRED MILES. DVORAK SATELLITE INTENSITY CLASSIFICATIONS ARE 3.0/4.0 FROM TAFB AND 3.0/3.5 FROM SAB. TAKING A BLEND OF THE INTENSITY ESTIMATES ALONG WITH THE CURRENT SATELLITE APPEARANCE...THE INITIAL INTENSITY HAS BEEN LOWERED TO 55 KT. THE INITIAL MOTION IS SLIGHTLY FASTER...ABOUT 300/13. A WEAK RIDGE NORTH OF THE CYCLONE IS EXPECTED TO PERSIST FOR THE NEXT DAY OR SO WHICH SHOULD RESULT IN A GENERAL WEST-NORTHWESTWARD MOTION. AFTER 24- TO 36-HOURS...LARGE DIVERGENCE IN MODEL GUIDANCE EXISTS WHEN A DEEP MID- TO UPPER-LEVEL TROUGH APPROACHES FROM THE WEST. ONE GROUP OF MODELS MAINTAINS KAREN AS A STRONGER CYCLONE AND TAKES THE SYSTEM TOWARD THE NORTHWEST IN RESPONSE TO THE TROUGH. THE SECOND GROUP FORECAST KAREN AS A MUCH WEAKER SYSTEM AND STEER IT WITH THE LOW-LEVEL FLOW. THE OFFICIAL TRACK FORECAST FOLLOWS THE LATTER SOLUTION...WHICH IS CLOSE WITH THE GFS AS WELL AS THE PREVIOUS ADVISORY PACKAGE. THE SHEAR IS EXPECTED TO REMAIN STRONG FOR THE NEXT 72 HOURS OR SO...WHICH WOULD LEAD TO A CONTINUED WEAKENING TREND OF THE CYCLONE. BY DAYS 4 AND 5...MOST OF THE MODEL GUIDANCE FORECASTS THE SHEAR TO DECREASE. HOWEVER...THE DECREASED SHEAR APPEARS TO BE RESULTANT OF KAREN APPROACHING THE AXIS OF THE AFOREMENTIONED TROUGH...WHICH WOULD NOT BE CONDUCIVE FOR MUCH STRENGTHENING EITHER. SIMILAR TO THE PREVIOUS FORECAST...THE OFFICIAL INTENSITY FORECAST CALLS FOR GRADUAL WEAKENING THROUGH FIVE DAYS. BUT...IF THE LOW-LEVEL CIRCULATION CENTER BECOMES FURTHER SEPARATED FROM THE DEEP CONVECTION...THE CYCLONE COULD WEAKER FASTER THAN INDICATED. NOAA BUOY 41041 REPORTED A MAXIMUM 1-MINUTE WIND OF 43 KT AROUND 0700 UTC...ABOUT 75 N MI NORTH OF THE ESTIMATED CENTER LOCATION. FORECAST POSITIONS AND MAX WINDS INITIAL 27/0900Z 13.6N 46.6W 55 KT 12HR VT 27/1800Z 14.6N 48.3W 50 KT 24HR VT 28/0600Z 15.8N 50.2W 50 KT 36HR VT 28/1800Z 16.9N 51.9W 45 KT 48HR VT 29/0600Z 18.1N 53.7W 45 KT 72HR VT 30/0600Z 20.0N 56.0W 40 KT 96HR VT 01/0600Z 21.5N 57.5W 40 KT 120HR VT 02/0600Z 23.0N 59.0W 40 KT $$ FORECASTER MAINELLI |
