000 WTNT42 KNHC 270847 TCDAT2 TROPICAL STORM PHILIPPE DISCUSSION NUMBER 13 NWS NATIONAL HURRICANE CENTER MIAMI FL AL172011 500 AM AST TUE SEP 27 2011 PHILIPPE HAS TAKEN ON THE APPEARANCE OF A SHEARED TROPICAL CYCLONE THIS MORNING. NIGHT CHANNEL VISIBLE IMAGERY AND RECENT MICROWAVE DATA INDICATE THAT THE LOW-LEVEL CENTER IS LOCATED NEAR THE WESTERN EDGE OF THE DEEP CONVECTION. THIS ASYMMETRIC CLOUD PATTERN IS DUE TO ABOUT 20 KT OF WEST-SOUTHWESTERLY WIND SHEAR...ACCORDING TO THE SHIPS MODEL. THE SATELLITE CLASSIFICATIONS HAVE CHANGED LITTLE SINCE THE TIME OF THE 2304 UTC ASCAT OVERPASS...SO THE INITIAL INTENSITY IS MAINTAINED AT 45 KT. THE AFOREMENTIONED SHEAR...WHICH IS BEING PRODUCED BY A DEEP-LAYER TROUGH TO THE NORTH OF PHILIPPE...IS NOT EXPECTED TO CHANGE MUCH DURING THE NEXT SEVERAL DAYS. AS A RESULT...THE SHIPS AND LGEM MODELS SHOW A VERY GRADUAL WEAKENING THROUGHOUT THE FORECAST PERIOD. CONVERSELY...THE REGIONAL HURRICANE MODELS SHOW PHILIPPE GAINING STRENGTH...ESPECIALLY BEYOND A COUPLE OF DAYS. GIVEN THE EXPECTED UNFAVORABLE ATMOSPHERIC ENVIRONMENT...THE OFFICIAL FORECAST FAVORS THE LGEM/SHIPS GUIDANCE AND IS AN UPDATE OF THE PREVIOUS ONE. THE TROPICAL STORM IS MOVING NORTHWESTWARD AT ABOUT 6 KT...LOCATED NEAR THE SOUTHWESTERN PERIPHERY OF A RIDGE OVER THE EASTERN ATLANTIC. THE RIDGE IS EXPECTED TO BUILD WESTWARD DURING THE NEXT 24 TO 36 HOURS AS THE TROUGH TO THE NORTH OF PHILIPPE LIFTS OUT. THIS FLOW PATTERN COULD ALLOW THE CYCLONE TO TURN A BIT TO THE LEFT WITH SOME INCREASE IN FORWARD SPEED DURING THAT TIME PERIOD. IN TWO TO THREE DAYS...ANOTHER TROUGH IS EXPECTED TO APPROACH BUT THEN BYPASS PHILIPPE...CAUSING IT TO TURN NORTHWARD. IN ITS WAKE...THE SUBTROPICAL RIDGE IS FORECAST TO REBUILD ONCE AGAIN...TURNING PHILIPPE BACK TOWARD THE NORTHWEST BY DAY 5. ALTHOUGH SIGNIFICANT SPREAD STILL EXISTS AMONGST THE MODELS...THEY HAVE COME INTO BETTER AGREEMENT IN THE OVERALL SYNOPTIC STEERING PATTERN. THE OFFICIAL FORECAST IS VERY CLOSE TO THE PREVIOUS ONE AND LIES A LITTLE TO THE WEST OF THE MULTI-MODEL CONSENSUS. FORECAST POSITIONS AND MAX WINDS INIT 27/0900Z 16.1N 35.1W 45 KT 50 MPH 12H 27/1800Z 16.7N 35.9W 45 KT 50 MPH 24H 28/0600Z 17.6N 37.1W 40 KT 45 MPH 36H 28/1800Z 18.7N 38.6W 40 KT 45 MPH 48H 29/0600Z 19.9N 39.6W 40 KT 45 MPH 72H 30/0600Z 22.3N 40.9W 35 KT 40 MPH 96H 01/0600Z 24.0N 41.5W 35 KT 40 MPH 120H 02/0600Z 25.0N 42.5W 35 KT 40 MPH $$ FORECASTER CANGIALOSI