ZCZC MIATCDAT4 ALL TTAA00 KNHC DDHHMM TROPICAL STORM DON DISCUSSION NUMBER 2 NWS NATIONAL HURRICANE CENTER MIAMI FL AL042011 1000 PM CDT WED JUL 27 2011 THE CLOUD PATTERN HAS NOT CHANGED SIGNIFICANTLY DURING THE PAST SEVERAL HOURS WITH THE EXCEPTION OF THE UPPER-LEVEL OUTFLOW THAT IS EXPANDING IN THE WESTERN PORTION OF THE CYCLONE. DEEP CONVECTION NEAR THE CENTER HAS DIMINISHED BUT THERE IS A CYCLONICALLY CURVED CONVECTIVE BAND TO THE SOUTH. T-NUMBERS HAVE NOT CHANGED AND THE INITIAL INTENSITY IS KEPT AT 35 KNOTS. ANOTHER RECONNAISSANCE PLANE IS SCHEDULED TO CHECK THE CYCLONE AT DAYBREAK. DON IS MOVING OVER WARM WATERS AND THE SHIPS GUIDANCE AS WELL AS MOST OF THE GLOBAL MODELS INDICATE THAT THE SHEAR IS LIKELY TO REMAIN RELATIVELY LOW...ALLOWING FOR SOME INTENSIFICATION. HOWEVER...NONE OF THE INTENSITY MODELS SHOW SIGNIFICANT STRENGTHENING. IT SHOULD BE NOTED THAT THE 48-HR OFFICIAL INTENSITY FORECAST OF 55 KT IS BEFORE LANDFALL...AND DON COULD GAIN SOME ADDITIONAL STRENGTH AS IT APPROACHES THE COAST. THE CYCLONE IS MOVING TOWARD THE WEST-NORTHWEST OR 300 DEGREES AT 10 KNOTS. THE RIDGE OVER THE SOUTHERN UNITED STATES CONTROLLING THE CURRENT MOTION OF DON IS EXPECTED TO PERSIST OR EVEN BUILD WESTWARD A LITTLE. THEREFORE...NO SIGNIFICANT CHANGE IN THE STEERING PATTERN IS ANTICIPATED...AND DON SHOULD CONTINUE TO MOVE ON THE SAME GENERAL WEST-NORTHWEST OR NORTHWEST TRACK TOWARD THE TEXAS COAST. THE TRACK GUIDANCE IS NOT IN QUITE AS GOOD AGREEMENT AS ONE WOULD LIKE TO SEE...HOWEVER. SOME MODELS LIKE THE GFDL AND GFDN BRING THE CYCLONE ON A MORE NORTHWESTERLY TRACK WHILE OTHERS...LIKE THE ECMWF...INDICATE A MORE WESTERLY MOTION. THE OFFICIAL FORECAST IS BASICALLY IN THE MIDDLE OF THE TWO OPTIONS. GIVEN THE CURRENT FORECAST TRACK AND UNCERTAINTIES... A TROPICAL STORM WATCH IS BEING ISSUED FOR A LARGE PORTION OF TEXAS COAST AT THIS TIME. FORECAST POSITIONS AND MAX WINDS INIT 28/0300Z 22.8N 88.1W 35 KT 40 MPH 12H 28/1200Z 23.6N 89.5W 40 KT 45 MPH 24H 29/0000Z 25.0N 91.5W 45 KT 50 MPH 36H 29/1200Z 26.2N 93.6W 50 KT 60 MPH 48H 30/0000Z 27.5N 96.0W 55 KT 65 MPH 72H 31/0000Z 29.5N 100.0W 25 KT 30 MPH...INLAND 96H 01/0000Z...DISSIPATED $$ FORECASTER AVILA NNNN
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Page last modified: Tuesday, 17-Jul-2012 13:43:45 UTC