ZCZC MIATCDAT4 ALL TTAA00 KNHC DDHHMM TROPICAL STORM MARIA DISCUSSION NUMBER 12 NWS NATIONAL HURRICANE CENTER MIAMI FL AL142011 1100 AM AST FRI SEP 09 2011 THERE HAS BEEN A SIGNIFICANT INCREASE IN DEEP CONVECTION OVERNIGHT AND THIS MORNING IN ASSOCIATION WITH MARIA. HOWEVER...THE OVERALL ORGANIZATION OF THE CYCLONE DOES NOT APPEAR TO HAVE CHANGED VERY MUCH. THE AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT HAS FOUND SOUTHWEST AND LIGHT WEST WINDS...BUT IT HAS NOT BEEN ABLE TO LOCATE A WELL-DEFINED LOW-LEVEL CENTER. HOWEVER...THERE ARE ENOUGH FLIGHT-LEVEL WINDS INDICATING A BROAD CLOSED CIRCULATION THAT JUSTIFIES MAINTAINING ADVISORIES ON THIS SYSTEM. THE AIRCRAFT HAS MEASURED A PEAK FLIGHT-LEVEL WIND OF 42 KT TO THE EAST OF THE CENTER...BUT HAS NOT YET SAMPLED THE NORTHEAST QUADRANT WHERE THE STRONGEST WINDS ARE LIKELY OCCURRING. THE INITIAL INTENSITY...THEREFORE HAS BEEN RAISED TO 40 KT...BASED ON DVORAK ESTIMATES OF 45 KT AND THE RECENT INCREASE IN DEEP CONVECTION. THE UPPER-LEVEL PATTERN AHEAD OF MARIA DOES NOT APPEAR TO BE VERY CONDUCIVE FOR SIGNIFICANT STRENGTHENING. AN UPPER-LEVEL LOW LOCATED TO THE NORTH OF THE LEEWARD ISLANDS IS EXPECTED TO PRODUCE MODERATE WEST TO SOUTHWEST SHEAR OVER THE CYCLONE DURING THE NEXT 2-3 DAYS...AND THE OFFICIAL FORECAST ONLY CALLS FOR SLIGHT STRENGTHENING DURING THAT TIME. LATER IN THE PERIOD THE UPPER-LEVEL ENVIRONMENT IS FORECAST TO BECOME MORE CONDUCIVE AND THE NHC FORECAST CALLS FOR STRENGTHENING...BUT NOT QUITE AS MUCH AS SHOWN BY MOST OF THE GUIDANCE. THE BEST ESTIMATE OF THE INITIAL MOTION IS 285/15. MARIA IS EXPECTED TO CONTINUE MOVING WEST-NORTHWESTWARD TO THE SOUTH OF A SUBTROPICAL RIDGE OVER THE CENTRAL AND WESTERN ATLANTIC. IN ABOUT 72 HOURS... THE WESTERN PORTION OF THE RIDGE IS FORECAST TO WEAKEN AS A TROUGH MOVES INTO THE SOUTHEASTERN UNITED STATES. THIS SHOULD RESULT IN A TURN TOWARD THE NORTHWEST AND NORTH NEAR THE END OF THE FORECAST PERIOD. HOWEVER...IT SHOULD BE NOTED THAT THE ECMWF MODEL DEPICTS A WEAKER CYCLONE THAT CONTINUES MORE WESTWARD. THE UPDATED NHC FORECAST IS SIMILAR TO THE PREVIOUS ADVISORY AND IS BETWEEN THE GFS..WHICH TURNS MARIA NORTHWARD IN 4-5 DAYS...AND THE AFOREMENTIONED ECMWF. FORECAST POSITIONS AND MAX WINDS INIT 09/1500Z 14.2N 57.5W 40 KT 45 MPH 12H 10/0000Z 15.1N 59.9W 45 KT 50 MPH 24H 10/1200Z 16.5N 62.4W 45 KT 50 MPH 36H 11/0000Z 17.9N 64.5W 45 KT 50 MPH 48H 11/1200Z 19.3N 66.5W 50 KT 60 MPH 72H 12/1200Z 22.0N 69.8W 55 KT 65 MPH 96H 13/1200Z 24.0N 72.0W 65 KT 75 MPH 120H 14/1200Z 27.5N 73.5W 70 KT 80 MPH $$ FORECASTER BROWN NNNN
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