ZCZC MIATCDAT2 ALL TTAA00 KNHC DDHHMM TROPICAL STORM PHILIPPE DISCUSSION NUMBER 26 NWS NATIONAL HURRICANE CENTER MIAMI FL AL172011 1100 AM AST FRI SEP 30 2011 FINALLY...WE CAN CLEARLY SEE THE CENTER OF PHILIPPE. A SERIES OF MICROWAVE PASSES FROM OVERNIGHT SUGGEST THAT THE PREVIOUSLY ESTIMATED CENTER DISSIPATED...AND A NEW CENTER FORMED FARTHER NORTH...CLOSER TO THE DEEP CONVECTION. NOW THERE IS NO DOUBT SINCE THE CENTER HAS RECENTLY POPPED OUT OF THIS DEEP CONVECTION. BECAUSE OF THE POSSIBLE RE-FORMATION...THE CENTER IS MOVING AT AN UNCERTAIN 325 DEGREES AT 11 KT. PHILIPPE IS STILL GAINING SOME LATITUDE AS IT MOVES AROUND THE SOUTHWESTERN PERIPHERY OF A MID-LEVEL ANTICYCLONE...BUT A NEW ANTICYCLONE IS ALREADY BUILDING FARTHER NORTH AND SHOULD FORCE THE STORM ON A WEST-NORTHWESTWARD HEADING OVER THE NEXT 48 HOURS. THE MODEL GUIDANCE IS TIGHTLY CLUSTERED DURING THIS PERIOD. THEREAFTER...THE GFS AND ECMWF INDICATE THAT THE MID-LEVEL HIGH WILL BUILD FARTHER SOUTH AND FORCE PHILIPPE ON A WEST TO JUST SOUTH OF DUE WEST HEADING ON DAYS 3 AND 4. ON THE OTHER HAND...MANY OF THE OTHER MODELS DO NOT BUILD THE RIDGE AS MUCH AND ALLOW THE CYCLONE TO CONTINUE GAINING LATITUDE. DESPITE THESE DIFFERENCES...PHILIPPE SHOULD HAVE MADE ENOUGH WESTWARD PROGRESS BY DAY 5 TO START FEELING THE INFLUENCE OF A DEEP LONGWAVE TROUGH OVER THE WESTERN ATLANTIC...AND ALL THE MODELS SHOW SOME DEGREE OF A NORTHWARD TURN BEGINNING AT THAT TIME. THE OFFICIAL FORECAST DIVERGES TO THE SOUTH OF THE TVCA CONSENSUS AFTER 48 HOURS IN THE DIRECTION OF THE GFS AND ECMWF...AND ENDS UP VERY CLOSE TO THE PREVIOUS FORECAST. A 1212 UTC ASCAT PASS SHOWED A FEW 40-KT WIND VECTORS JUST TO THE NORTH OF THE CENTER...AND THE INITIAL INTENSITY IS RAISED TO 45 KT. HOWEVER...PHILIPPE WILL LIKELY NOT MAINTAIN THIS INTENSITY NOW THAT VERTICAL SHEAR IS INCREASING OVER THE SYSTEM. BELLIGERENT NORTHERLY SHEAR OF AT LEAST 30 KT IS EXPECTED TO AFFECT PHILIPPE OVER THE NEXT SEVERAL DAYS...AND THIS COULD CAUSE THE SYSTEM TO WEAKEN TO A DEPRESSION. THE SHEAR COULD RELAX A BIT BY DAY 5 ONCE THE CYCLONE REACHES AN AREA OF UPPER-LEVEL RIDGING BETWEEN THE HOSTILE NORTHERLY WINDS OVER THE CENTRAL ATLANTIC AND THE DEEP TROUGH OVER THE WESTERN ATLANTIC. THE FORECAST THEREFORE ALLOWS FOR PHILIPPE TO REGAIN TROPICAL-STORM STATUS AT THAT TIME. IN GENERAL...THE OFFICIAL INTENSITY FORECAST LIES BETWEEN THE LGEM AND THE SHIPS MODEL...THE LATTER OF WHICH MAINTAINS PHILIPPE AS A TROPICAL STORM THROUGHOUT THE FORECAST PERIOD. FORECAST POSITIONS AND MAX WINDS INIT 30/1500Z 22.9N 45.3W 45 KT 50 MPH 12H 01/0000Z 23.8N 46.7W 40 KT 45 MPH 24H 01/1200Z 24.6N 48.5W 40 KT 45 MPH 36H 02/0000Z 25.3N 50.2W 40 KT 45 MPH 48H 02/1200Z 25.7N 51.8W 35 KT 40 MPH 72H 03/1200Z 25.5N 55.5W 30 KT 35 MPH 96H 04/1200Z 25.0N 60.0W 30 KT 35 MPH 120H 05/1200Z 26.0N 62.5W 35 KT 40 MPH $$ FORECASTER BERG NNNN
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