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| #464099 (Received by flhurricane at: 4:35 PM 04.Oct.2011) TCDAT2 TROPICAL STORM PHILIPPE DISCUSSION NUMBER 43 NWS NATIONAL HURRICANE CENTER MIAMI FL AL172011 500 PM AST TUE OCT 04 2011 THE STRUCTURE OF PHILIPPE HAS CHANGED LITTLE OVER THE PAST FEW HOURS WITH THE LOW-LEVEL CENTER LOCATED NEAR THE NORTHERN EDGE OF THE DEEP CONVECTION. ALTHOUGH DVORAK FINAL-T NUMBERS FROM TAFB AND SAB HAVE FALLEN TO 45 KT...AN ASCAT PASS FROM 1410 UTC SHOWED A FEW 50 KT BARBS IN THE CONVECTION TO THE EAST OF THE CENTER. THE INTENSITY IS THEREFORE HELD AT 55 KT. GLOBAL MODEL FIELDS SUGGEST THAT THE STRONG NORTHERLY SHEAR WHICH HAS BEEN AFFECTING PHILIPPE FOR THE PAST 4 DAYS SHOULD ABATE IN THE NEXT 24 HOURS...LEAVING THE CYCLONE IN A FAVORABLE BUT SMALL REGION OF UPPER-LEVEL RIDGING. THIS SHOULD ALLOW FOR SOME STRENGTHENING...AND THE OFFICIAL FORECAST CONTINUES TO SHOW PHILIPPE BECOMING A HURRICANE IN THE 36-48 HOUR TIME FRAME. STRONG SOUTHWESTERLY SHEAR IS THEN EXPECTED TO DEVELOP OVER PHILIPPE AFTER 48 HOURS...YET FOR THE MOST PART THE INTENSITY MODELS DO NOT SHOW MUCH WEAKENING. THE ONE EXCEPTION IS THE LGEM...WHICH TENDS TO HANDLE SHEAR BETTER THAN THE OTHER MODELS TOWARD THE LATTER PART OF THE FORECAST PERIOD AND IS AT THE LOWER END OF THE GUIDANCE AT THIS TIME. THE OFFICIAL FORECAST IS VERY CLOSE TO THE MODEL CONSENSUS FOR MOST OF THE PERIOD...AND IT IS HIGHER THAN THE LGEM AT DAY 5 DUE TO THE POSSIBILITY OF SOME BAROCLINIC FORCING AS PHILIPPE BECOMES EXTRATROPICAL. THE LOW-LEVEL CENTER HAS BECOME A LITTLE DIFFICULT TO LOCATE THIS AFTERNOON...BUT THE LOW-CLOUD LINES SUGGEST TO ME THAT IT HAS EITHER JUMPED TO THE NORTH...OR THE LOW-LEVEL CIRCULATION IS BECOMING SOMEWHAT ELONGATED. REGARDLESS...PHILIPPE HAS AN AVERAGED INITIAL MOTION OF 280 DEGREES AT 9 KT AND IS ABOUT START ITS SHARP RE-CURVATURE. THE TRACK GUIDANCE IS IN GOOD AGREEMENT AT LEAST FOR THE FIRST 72 HOURS...BUT AS HAS BEEN THE CASE FOR SEVERAL DAYS NOW...THE ECMWF IS ON THE EASTERN AND SOUTHERN SIDE OF THE GUIDANCE WHILE THE GFS IS FARTHER WEST AND NORTH. THE ECMWF ALSO APPEARS TO DIFFER FROM THE OTHER GLOBAL MODELS BY HAVING PHILIPPE STAY FARTHER SOUTH AND BE ABSORBED BY A COLD FRONT WHEREAS THE OTHER MODELS SHOW IT BECOMING THE MAIN THE PARENT CYCLONE OF THE FRONTAL SYSTEM. THE NEW OFFICIAL FORECAST IS SHIFTED A BIT TO THE EAST OF THE PREVIOUS ONE FOR THE FIRST 48 HOURS BUT IS THEN VERY SIMILAR ON DAYS 3 THROUGH 5...FOLLOWING THE IDEA THAT PHILIPPE WILL BE MOVING NORTHEASTWARD AS AN EXTRATROPICAL CYCLONE ON DAY 5. FORECAST POSITIONS AND MAX WINDS INIT 04/2100Z 24.1N 60.0W 55 KT 65 MPH 12H 05/0600Z 24.5N 61.1W 55 KT 65 MPH 24H 05/1800Z 25.2N 61.7W 60 KT 70 MPH 36H 06/0600Z 26.3N 61.7W 65 KT 75 MPH 48H 06/1800Z 27.3N 60.8W 65 KT 75 MPH 72H 07/1800Z 29.5N 57.0W 60 KT 70 MPH 96H 08/1800Z 32.0N 50.5W 55 KT 65 MPH 120H 09/1800Z 36.5N 46.0W 55 KT 65 MPH...POST-TROP/EXTRATROP $$ FORECASTER BERG |
