000 WTNT42 KNHC 250255 TCDAT2 TROPICAL STORM PHILIPPE DISCUSSION NUMBER 4 NWS NATIONAL HURRICANE CENTER MIAMI FL AL172011 1100 PM AST SAT SEP 24 2011 A 2344 UTC ASCAT PASS OVER PHILIPPE INDICATES THE LOW-LEVEL CENTER IS LOCATED VERY NEAR A RECENT BURST OF DEEP CONVECTION...BUT THAT THE MAXIMUM WINDS ARE PROBABLY BARELY 35 KT. SINCE THE CONVECTION HAS BEEN ON A GENERAL UPWARD TREND OVER THE PAST COUPLE OF HOURS...THE INITIAL INTENSITY IS HELD AT 35 KT. PHILIPPE IS LOCATED ON THE SOUTHERN PERIPHERY OF A WEAK MID-LEVEL RIDGE...AND THAT RIDGE IS EXPECTED TO SHIFT EASTWARD AND STRENGTHEN NEAR THE AFRICAN COAST IN THE COMING DAYS AS A DEEP TROUGH DIGS OVER THE CENTRAL ATLANTIC. THEREFORE...THE MOTION OF THE CYCLONE...WHICH IS CURRENTLY 295/10 KT...IS FORECAST TO TURN NORTHWESTWARD AND SLOW DOWN AS PHILIPPE MOVES BETWEEN THESE TWO SYNOPTIC FEATURES. THERE IS VERY GOOD AGREEMENT AMONG THE MODELS UNTIL ABOUT 72 HOURS...AFTER WHICH TIME THE GFS AND ECMWF SHOW A SLOWER AND WESTWARD-LEANING MOTION WHILE THE BULK OF THE OTHER MODELS INDICATE A TURN TOWARD THE NORTH AND NORTH-NORTHEAST. A SLOWER MOTION IS FAVORED SINCE THERE IS A LOT OF UNCERTAINTY...AND THE OFFICIAL FORECAST ENDS UP CLOSE TO THE GFS BY DAY 5. THE FORECAST TRACK OF PHILIPPE NEVER REALLY TAKES THE CYCLONE OVER SIGNIFICANTLY WARMER WATERS...AND THE UNDERLYING OCEAN SHOULD DEFINITELY BE COOLER AFTER ABOUT 48 HOURS. IN ADDITION...PHILIPPE SHOULD BE MOVING OUT OF AN ENVIRONMENT OF LIGHT UPPER-LEVEL WINDS INTO AN AREA OF STRONGER SOUTHWESTERLY SHEAR IN ABOUT 3 DAYS. THEREFORE...STRENGTHENING IS EXPECTED MAINLY DURING THE NEXT 48 HOURS WITH SOME WEAKENING POSSIBLE BY DAYS 4 AND 5. THE OFFICIAL FORECAST LIES GENERALLY CLOSE TO THE INTENSITY CONSENSUS AND SHOWS PHILIPPE BECOMING A HURRICANE IN THE 48-72 HOUR TIME FRAME. FORECAST POSITIONS AND MAX WINDS INIT 25/0300Z 11.6N 28.8W 35 KT 40 MPH 12H 25/1200Z 12.1N 30.5W 40 KT 45 MPH 24H 26/0000Z 13.1N 32.5W 50 KT 60 MPH 36H 26/1200Z 14.1N 34.1W 55 KT 65 MPH 48H 27/0000Z 15.4N 35.3W 65 KT 75 MPH 72H 28/0000Z 18.0N 37.0W 65 KT 75 MPH 96H 29/0000Z 21.0N 38.0W 60 KT 70 MPH 120H 30/0000Z 24.0N 38.0W 60 KT 70 MPH $$ FORECASTER BERG