000 WTNT44 KNHC 112039 TCDAT4 TROPICAL STORM MARIA DISCUSSION NUMBER 21 NWS NATIONAL HURRICANE CENTER MIAMI FL AL142011 500 PM AST SUN SEP 11 2011 MARIA REMAINS A SHEARED TROPICAL CYCLONE. SEVERAL LOW-LEVEL CLOUD SWIRLS HAVE BEEN SEEN ROTATING AROUND THE EXPOSED MEAN CIRCULATION CENTER. POSITION ESTIMATES FROM THE UNITED STATES AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT WERE A BIT SCATTERED AS THEY FIXED THE DIFFERENT SWIRLS DURING THE FLIGHT. THE AIRCRAFT REPORTED PEAK 850 MB FLIGHT-LEVEL WINDS OF 53 KT AND BELIEVABLE SFMR WINDS OF 45-48 KT...WHICH SUPPORT AN INITIAL INTENSITY OF 50 KT. THE UPPER-LEVEL WIND PATTERN IS PREDICTED TO REMAIN HOSTILE BY THE GLOBAL MODELS DURING THE NEXT 24-36 HOURS. HOWEVER...THE UPPER-LEVEL WINDS COULD BECOME A LITTLE MORE CONDUCIVE IN 2-3 DAYS AS AN UPPER-LEVEL RIDGE IS FORECAST TO BUILD NORTHEAST OF THE BAHAMAS. THIS WINDOW OF OPPORTUNITY FOR STRENGTHENING APPEARS AS THOUGH IT WILL BE SHORT...AS STRONG SOUTHWESTERLY SHEAR ASSOCIATED A MID-LATITUDE TROUGH IMPINGES ON THE CYCLONE BY 96 HOURS. AFTER THAT...MARIA IS FORECAST TO INTERACT WITH A FRONTAL BOUNDARY AND BECOME AN EXTRATROPICAL CYCLONE BY 120 HOURS. THE CENTROID OF THE LARGER CIRCULATION IS LOCATED A LITTLE NORTH OF THE PREVIOUS ADVISORY ESTIMATE...WHICH REQUIRED A SLIGHT RELOCATION. SMOOTHING THROUGH THE FIXES DURING THE PAST 12 HOURS OR SO YIELDS AN INITIAL MOTION ESTIMATE OF 300/9 KT. MARIA SHOULD MOVE WEST- NORTHWESTWARD TO NORTHWESTWARD DURING THE NEXT DAY OR SO... THEN TURN NORTHWARD AHEAD OF A TROUGH APPROACHING THE EAST COAST OF THE UNITED STATES. MARIA SHOULD RECURVE NORTHEASTWARD AHEAD OF A SECOND TROUGH MOVING THROUGH THE GREAT LAKES AND NORTHEAST UNITED STATES DURING THE 3-5 DAY TIME PERIOD. THE TRACK GUIDANCE HAS COME INTO BETTER AGREEMENT THIS CYCLE WITH THE ECMWF SHIFTING EASTWARD...AND CLOSER TO THE GFS TRACK. THE NEW NHC TRACK IS ESSENTIALLY AN UPDATE OF THE PREVIOUS ADVISORY. ALTHOUGH THE STRONGEST WINDS WILL REMAIN OVER WATER TO THE NORTH OF THE NORTHERN CARIBBEAN ISLANDS...WIND GUSTS TO TROPICAL STORM FORCE ARE POSSIBLE IN THE RAIN BANDS CURRENTLY OVER THE LEEWARD ISLANDS. THESE SHOWERS AND THUNDERSTORMS ARE EXPECTED TO SPREAD OVER THE VIRGIN ISLANDS AND PUERTO RICO TONIGHT AND MONDAY. FORECAST POSITIONS AND MAX WINDS INIT 11/2100Z 19.8N 65.2W 50 KT 60 MPH 12H 12/0600Z 20.6N 66.3W 50 KT 60 MPH 24H 12/1800Z 21.7N 67.6W 50 KT 60 MPH 36H 13/0600Z 22.8N 68.7W 50 KT 60 MPH 48H 13/1800Z 24.2N 69.4W 55 KT 65 MPH 72H 14/1800Z 29.3N 69.2W 65 KT 75 MPH 96H 15/1800Z 37.5N 64.5W 65 KT 75 MPH 120H 16/1800Z 49.5N 51.5W 60 KT 70 MPH...POST-TROP/EXTRATROP $$ FORECASTER BROWN