000 WTNT44 KNHC 080308 TCDAT4 TROPICAL STORM MARIA DISCUSSION NUMBER 6 NWS NATIONAL HURRICANE CENTER MIAMI FL AL142011 1100 PM AST WED SEP 07 2011 MARIA HAS CHANGED LITTLE IN ORGANIZATION OVER THE PAST SEVERAL HOURS...WITH THE LOW-LEVEL CENTER DISPLACED TO THE SOUTHWESTERN EDGE OF THE DEEP CONVECTION BY SOUTHWESTERLY VERTICAL WIND SHEAR. SATELLITE INTENSITY ESTIMATES ARE 45 KT FROM TAFB AND 35 KT FROM SAB...WHILE NOAA BUOY 41041 JUST REPORTED 1-MINUTE MEAN WINDS OF 43 KT. BASED ON THIS THE INITIAL INTENSITY REMAINS 45 KT. THE INITIAL MOTION IS A FAST 275/20. MARIA IS CURRENTLY ON THE SOUTH SIDE OF A STRONG LOW/MID-LEVEL SUBTROPICAL RIDGE...AND THIS SHOULD KEEP THE STORM MOVING QUICKLY WESTWARD FOR THE NEXT 24 HOURS OR SO. FROM 24-72 HOURS...MARIA SHOULD APPROACH A WEAKNESS IN THE RIDGE CAUSED BY AN UPPER-LEVEL LOW...WHICH SHOULD ALLOW THE CYCLONE TO TURN WEST-NORTHWESTWARD WITH SOME DECREASE IN FORWARD SPEED. THE FORECAST TRACK IS MORE UNCERTAIN AFTER 72 HOURS AS MARIA APPROACHES THE WESTERN END OF THE SUBTROPICAL RIDGE AND A DEEP-LAYER TROUGH MOVES EASTWARD THROUGH THE EASTERN UNITED STATES. WHILE THE GUIDANCE GENERALLY SHOWS A TURN TOWARD THE NORTHWEST... THERE IS A SIGNIFICANT SPREAD BETWEEN THE MORE WESTERLY GFDL/ECMWF AND THE MORE EASTERLY GFS/NOGAPS. THE NEW FORECAST TRACK IS SHIFTED A LITTLE TO THE SOUTH OF THE PREVIOUS TRACK DURING THE FIRST 48 HOURS...THEN IS CLOSE TO THE THE PREVIOUS TRACK AFTER THAT TIME. THE NEW TRACK LIES CLOSE TO THE CENTER OF THE GUIDANCE ENVELOPE AND THE VARIOUS CONSENSUS MODELS. SIGNIFICANT SOUTHWESTERLY TO WESTERLY SHEAR IS EXPECTED TO CONTINUE FOR THE NEXT 48-72 HOURS...AND THE NEW INTENSITY FORECAST CONTINUES TO CALL FOR LITTLE CHANGE IN STRENGTH DURING THAT TIME. AFTER THAT THERE IS A POSSIBILITY THAT MARIA MAY FIND A DECREASED SHEAR ENVIRONMENT...ALTHOUGH THE FORECAST PRESENCE OF THE UPPER-LEVEL LOW NEAR THE STORM MAKES THIS UNCERTAIN. ALL THE INTENSITY GUIDANCE SHOWS STRENGTHENING AFTER 72 HOURS...SO THE INTENSITY FORECAST NOW CALLS FOR SOME MODEST STRENGTHENING DURING THAT TIME. FORECAST POSITIONS AND MAX WINDS INIT 08/0300Z 13.4N 46.2W 45 KT 50 MPH 12H 08/1200Z 13.7N 49.2W 45 KT 50 MPH 24H 09/0000Z 14.3N 53.3W 45 KT 50 MPH 36H 09/1200Z 15.1N 56.7W 45 KT 50 MPH 48H 10/0000Z 16.1N 59.7W 45 KT 50 MPH 72H 11/0000Z 19.0N 64.5W 45 KT 50 MPH 96H 12/0000Z 22.5N 68.5W 50 KT 60 MPH 120H 13/0000Z 25.5N 71.0W 60 KT 70 MPH $$ FORECASTER BEVEN