000 WTNT42 KNHC 260245 TCDAT2 TROPICAL STORM KAREN DISCUSSION NUMBER 5 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL122007 1100 PM EDT TUE SEP 25 2007 AFTER LOOKING RATHER UNIMPRESSIVE IN INFRARED SATELLITE IMAGERY DURING THE AFTERNOON...DEEP CONVECTION HAS REDEVELOPED NEAR THE CENTER OF KAREN AND BANDING FEATURES HAVE BECOME A LITTLE BETTER DEFINED WITHIN THE PAST COUPLE OF HOURS. HOWEVER... SATELLITE INTENSITY ESTIMATES AND QUIKSCAT DATA SUGGEST THAT THE MAXIMUM WINDS REMAIN 35 KT. THE INITIAL MOTION IS 285/12. THE TRACK FORECAST SCENARIO REMAINS THE SAME WITH KAREN MOVING WEST-NORTHWESTWARD SOUTH OF A DEEP-LAYER RIDGE DURING THE NEXT COUPLE OF DAYS. THEREAFTER...A WEAKNESS IN THE RIDGE IS EXPECTED TO DEVELOP OVER THE CENTRAL ATLANTIC... ALLOWING A TURN TOWARD THE NORTHWEST. THE GFS AND UKMET MODELS...WHICH HAVE PERFORMED WELL IN THE ATLANTIC SO FAR THIS YEAR...ARE ALONG THE SOUTHERN EDGE OF THE GUIDANCE ENVELOPE AND THE OFFICIAL FORECAST LEANS TOWARDS THESE SOLUTIONS. THE LARGE AND BROAD CIRCULATION OF KAREN HAS LIKELY INHIBITED STRENGTHENING DURING THE PAST 24 HOURS. WITH THE RECENT DEVELOPMENT OF CONVECTION NEAR THE CENTER AND THE FACT THAT THE UPPER-LEVEL OUTFLOW HAS CONTINUED TO BECOME BETTER ESTABLISHED...IT APPEARS THAT KAREN SHOULD STRENGTHEN DURING THE NEXT DAY OR TWO. THEREAFTER...IT REMAINS UNCLEAR AS TO EXACTLY WHAT ROLE A DEVELOPING UPPER-LEVEL TROUGH NORTHEAST OF THE LEEWARD ISLANDS WILL HAVE ON THE CYCLONE. THE GFS DEVELOPS THIS TROUGH A LITTLE FARTHER WEST THAN THE REMAINDER OF THE DYNAMICAL MODELS AND KEEPS A MORE FAVORABLE OUTFLOW PATTERN OVER KAREN FOR A LITTLE LONGER. HOWEVER...BY DAYS 4-5...KAREN IS FORECAST TO MOVE CLOSE ENOUGH TO THE UPPER-LEVEL TROUGH THAT SOUTHWESTERLY SHEAR WOULD INCREASE. DESPITE THIS SEEMINGLY UNFAVORABLE ENVIRONMENT LATE IN THE FORECAST PERIOD...THE GFDL AND HWRF MODELS CONTINUE TO STRENGTHEN KAREN TO A HURRICANE. THE SHIPS AND LGEM MODELS SHOW LITTLE CHANGE IN STRENGTH AFTER 48-72 HOURS. THE OFFICIAL INTENSITY FORECAST BLENDS THE STATISTICAL MODELS AND SHOWS A LITTLE LESS INTENSIFICATION THAN IN THE PREVIOUS ADVISORY. FORECAST POSITIONS AND MAX WINDS INITIAL 26/0300Z 11.1N 41.0W 35 KT 12HR VT 26/1200Z 11.6N 43.0W 40 KT 24HR VT 27/0000Z 12.6N 45.5W 45 KT 36HR VT 27/1200Z 13.8N 47.6W 50 KT 48HR VT 28/0000Z 15.3N 49.4W 55 KT 72HR VT 29/0000Z 17.7N 51.4W 55 KT 96HR VT 30/0000Z 20.0N 53.0W 50 KT 120HR VT 01/0000Z 22.5N 54.5W 50 KT $$ FORECASTER BROWN