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#153138 (Received by flhurricane at: 4:37 AM 30.Sep.2007) TCDAT4 TROPICAL STORM MELISSA DISCUSSION NUMBER 8 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL142007 500 AM EDT SUN SEP 30 2007 STRONG WESTERLY SHEAR IS GETTING THE BEST OF MELISSA AND THE LOW-LEVEL CIRCULATION RECENTLY BECAME EXPOSED. NEW CONVECTION HAS FORMED NEAR THE CIRCULATION CENTER BUT IS ALREADY SHOWING SIGNS OF BEING SHUNTED EASTWARD. BASED ON THE DEGRADED SATELLITE PRESENTATION...THE INITIAL INTENSITY IS LOWERED TO 35 KT. WITH THE SHEAR EXPECTED TO INCREASE AND THE SSTS EXPECTED TO DECREASE IN A DAY OR SO...MELISSA COULD STRUGGLE TO GENERATE PERSISTENT DEEP CONVECTION AND MAINTAIN ITS STATUS AS A TROPICAL CYCLONE. DEGENERATION TO A REMNANT LOW IS EXPECTED IN ABOUT 3 DAYS...IF NOT SOONER. MELISSA HAS PICKED UP FORWARD SPEED WITH THE INITIAL MOTION ESTIMATE NOW 295/11. THE TRACK FORECAST IS STRONGLY DEPENDENT ON HOW LONG MELISSA CAN MAINTAIN APPRECIABLE VERTICAL DEPTH. THE DYNAMICAL MODELS ARE ESSENTIALLY SPLIT INTO TWO CAMPS. THE NOGAPS AND UKMET MODELS SHOW MELISSA REMAINING A RELATIVELY DEEP CYCLONE WITH A SHARP NORTHEASTWARD TURN BEYOND 48 HOURS IN RESPONSE TO A MIDDLE- TO UPPER-LEVEL TROUGH EXPECTED TO DEVELOP OVER THE CENTRAL ATLANTIC. THE WEAKER AND SHALLOWER HWRF AND ECMWF SOLUTIONS FOR THE CYCLONE SHOW AN ALMOST INSTANT TURN WESTWARD. SINCE THE OFFICIAL FORECAST ASSUMES MELISSA WILL BE ABLE TO GENERATE INTERMITTENT BURSTS OF CONVECTION DURING THE NEXT DAY OR TWO...THE TRACK FORECAST LIES IN BETWEEN THESE TWO SCENARIOS BUT IS SOUTH OF THE DYNAMICAL MODEL CONSENSUS. FORECAST POSITIONS AND MAX WINDS INITIAL 30/0900Z 16.5N 31.4W 35 KT 12HR VT 30/1800Z 17.2N 33.0W 35 KT 24HR VT 01/0600Z 18.3N 35.1W 30 KT 36HR VT 01/1800Z 19.3N 37.1W 30 KT 48HR VT 02/0600Z 20.5N 39.2W 30 KT 72HR VT 03/0600Z 23.0N 42.5W 25 KT...REMNANT LOW 96HR VT 04/0600Z 26.0N 44.5W 20 KT...REMNANT LOW 120HR VT 05/0600Z...DISSIPATED $$ FORECASTER RHOME |