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| #6134 (Received by flhurricane at: 4:52 AM 26.Aug.2004) TCDAT1 TROPICAL STORM FRANCES DISCUSSION NUMBER 6 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 5 AM EDT THU AUG 26 2004 THE CLOUD PATTERN IS BETTER ORGANIZED WITH A WELL-DEFINED CURVED CLOUD BAND...DEEP CONVECTION NEAR THE CENTER AND GOOD OUTFLOW. IN FACT...THERE WERE SOME INDICATIONS THAT A BANDING-TYPE EYE WAS TRYING TO FORM IN EARLIER IMAGES. INITIAL INTENSITY HAS BEEN INCREASED TO 50 KNOTS BUT IF THE FORMATION OF THE EYE MATERIALIZES ...WINDS COULD BE HIGHER THAN CURRENTLY ESTIMATED. BECAUSE THE SHEAR IS LOW AND THE OCEAN IS WARM STRENGTHENING IS INDICATED. THIS FORECAST IS IN AGREEMENT WITH THE GFDL AND SHIPS MODELS WHICH BRING FRANCES TO NEAR 95 KNOTS. LATER IN THE PERIOD...A TURN OF THE CYCLONE TO THE NORTHWEST MORE THAN INDICATED IN THE FORECAST COULD BRING FRANCES TO A LESS FAVORABLE UPPER-LEVEL WIND ENVIRONMENT. FRANCES IS MOVING TOWARD THE WEST-NORTHWEST OR 290 DEGREES AT 15 KNOTS. GLOBAL MODELS CONTINUE TO FORECAST A MID-LEVEL TROUGH OVER THE CENTRAL ATLANTIC. IN THE SHORT TERM...THIS FEATURE WILL LIKELY ERODE THE SUBTROPICAL RIDGE FORCING FRANCES TO MOVE TOWARD THE WEST-NORTHWEST AND NORTHWEST WITH A DECREASE IN FORWARD SPEED. THEREAFTER...ONCE THE TROUGH MOVES OUT OR WEAKENS...MODELS ARE UNANIMOUSLY REDEVELOPING THE SUBTROPICAL RIDGE TO THE NORTH OF FRANCES. THIS WILL LIKELY RESULT ON A TRACK BACK TO WEST-NORTHWEST OR EVEN TOWARD THE WEST DEPENDING OF THE INTENSITY OF THE RIDGE. BOTH THE GFS AND THE CANADIAN GLOBAL MODELS DEVELOP A STRONGER RIDGE AND CONSEQUENTLY MOVE THE CYCLONE MORE TO THE WEST NEAR OR OVER THE NORTHERN LEEWARD ISLANDS. THE UK AND THE NOGAPS DEVELOP A WEAKER RIDGE ALLOWING THE CYCLONE TO MOVE WELL-NORTH OF THE LEEWARD ISLANDS. THE OFFICIAL FORECAST IS IN BETWEEN THESE TWO OPTIONS. IT IS SIGNIFICANT THAT EACH NEW RUN OF THE GLOBAL MODELS HAS A FORECAST TRACK FARTHER TO WEST...SO IF THIS TREND CONTINUES...THERE WILL BE INTERESTING DAYS AHEAD. FORECASTER AVILA FORECAST POSITIONS AND MAX WINDS INITIAL 26/0900Z 12.6N 43.7W 50 KT 12HR VT 26/1800Z 13.3N 45.8W 65 KT 24HR VT 27/0600Z 14.5N 48.0W 70 KT 36HR VT 27/1800Z 16.0N 50.0W 80 KT 48HR VT 28/0600Z 17.0N 51.5W 90 KT 72HR VT 29/0600Z 18.5N 53.0W 90 KT 96HR VT 30/0600Z 19.5N 55.0W 90 KT 120HR VT 31/0600Z 20.9N 59.0W 90 KT |
