000 WTNT44 KNHC 120844 TCDAT4 TROPICAL STORM MARIA DISCUSSION NUMBER 23 NWS NATIONAL HURRICANE CENTER MIAMI FL AL142011 500 AM AST MON SEP 12 2011 MARIA REMAINS A STRONGLY SHEARED TROPICAL CYCLONE WITH DEEP CONVECTION CONFINED TO THE EASTERN HALF OF THE CIRCULATION. DVORAK CLASSIFICATIONS WERE ESSENTIALLY UNCHANGED SINCE 0000 UTC...SO THE INITIAL WIND SPEED IS HELD AT 50 KT. BUOY 41043 LOCATED ABOUT 75 N MI EAST OF THE ESTIMATED CENTER HAS REPORTED SUSTAINED WINDS AS HIGH AS 41 KT DURING THE PAST FEW HOURS. THE LOW-LEVEL CENTER OF MARIA IS VERY DIFFICULT TO LOCATE. USING A SSMIS PASS AROUND 0000 UTC AND CONTINUITY...THE INITIAL MOTION ESTIMATE IS 305/8. GLOBAL MODELS ARE IN GOOD AGREEMENT ON THE LARGE SCALE PATTERN EVOLUTION THAT WILL AFFECT THE FUTURE TRACK OF MARIA. A MID- TO UPPER-LEVEL TROUGH CURRENTLY OVER THE EASTERN UNITED STATES IS EXPECTED TO MOVE EASTWARD AND CAUSE MARIA TO GRADUALLY TURN TOWARD THE NORTH DURING THE NEXT 48 HOURS. ANOTHER TROUGH...THIS ONE BEING LARGER AND STRONGER...WILL MOVE OVER ATLANTIC CANADA AND THE NORTHEAST UNITED STATES LATE THIS WEEK. THIS FLOW PATTERN SHOULD THEN TURN MARIA TO THE NORTHEAST WITH A SIGNIFICANT INCREASE IN FORWARD SPEED. WESTERLY SHEAR OF ABOUT 20 KT...PRIMARILY ASSOCIATED WITH AN UPPER-LEVEL LOW TO THE NORTHWEST OF THE CYCLONE...IS CURRENTLY AFFECTING MARIA. THE SHIPS MODEL ONLY SHOWS A SLIGHT DECREASE IN THE SHEAR DURING THE NEXT COUPLE OF DAYS BEFORE IT INCREASES SHARPLY IN ABOUT 72 HOURS. THIS UNFAVORABLE ATMOSPHERIC ENVIRONMENT...COMBINED WITH A COLD WATER WAKE LEFT BY HURRICANE KATIA SHOULD LIMIT THE INTENSIFICATION PROCESS. THE OFFICIAL FORECAST REMAINS ON THE LOW END OF THE MODEL GUIDANCE NEAR THE LGEM. THE AFOREMENTIONED STRONG SHEAR...THE INTERACTION WITH A FRONT...AND SEA SURFACE TEMPERATURES LOWER THAN 20C SHOULD CAUSE MARIA TO TRANSITION TO AN EXTRATROPICAL CYCLONE IN ABOUT FOUR DAYS. THE 12-FT SEA RADII HAVE BEEN MODIFIED BASED ON A 0340 UTC ALTIMETER PASS. FORECAST POSITIONS AND MAX WINDS INIT 12/0900Z 20.8N 66.3W 50 KT 60 MPH 12H 12/1800Z 21.5N 67.2W 50 KT 60 MPH 24H 13/0600Z 22.7N 68.3W 50 KT 60 MPH 36H 13/1800Z 24.0N 69.0W 55 KT 65 MPH 48H 14/0600Z 26.1N 69.2W 55 KT 65 MPH 72H 15/0600Z 32.8N 67.6W 65 KT 75 MPH 96H 16/0600Z 41.5N 60.5W 60 KT 70 MPH...POST-TROP/EXTRATROP 120H 17/0600Z 51.0N 46.0W 50 KT 60 MPH...POST-TROP/EXTRATROP $$ FORECASTER CANGIALOSI