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| #460978 (Received by flhurricane at: 10:44 PM 21.Sep.2011) TCDAT1 TROPICAL STORM OPHELIA DISCUSSION NUMBER 5 NWS NATIONAL HURRICANE CENTER MIAMI FL AL162011 1100 PM AST WED SEP 21 2011 INFRARED AND MICROWAVE SATELLITE IMAGERY THIS EVENING SHOWS THAT OPHELIA CONTINUES TO BE AFFECTED BY SOUTHWESTERLY VERTICAL WIND SHEAR...WITH THE LOW-LEVEL CENTER REMAINING NEAR THE SOUTHWESTERN EDGE OF THE MAIN CONVECTIVE MASS. SATELLITE INTENSITY ESTIMATES FROM TAFB AND SAB ARE 45 KT...AND NOAA BUOY 41041 RECENTLY REPORTED 1-MINUTE MEAN WINDS OF 45 KT. BASED ON THE BUOY AND THE LIKELIHOOD THAT IT DID NOT SAMPLE THE MAXIMUM WIND...THE INITIAL INTENSITY REMAINS 50 KT. THE INITIAL MOTION IS 280/13. THERE IS LITTLE CHANGE TO EITHER THE TRACK FORECAST PHILOSOPHY OR THE FORECAST TRACK SINCE THE LAST ADVISORY. A LOW/MID-LEVEL RIDGE TO THE NORTH OF OPHELIA SHOULD STEER THE CYCLONE WESTWARD TO WEST-NORTHWESTWARD FOR THE NEXT 2-3 DAYS. AFTER THAT TIME...THE STORM SHOULD APPROACH THE WESTERN PERIPHERY OF THE RIDGE AS A DEEP-LAYER TROUGH MOVES EASTWARD INTO THE EASTERN UNITED STATES. THIS SHOULD ALLOW OPHELIA TO TURN TOWARD THE NORTHWEST WITH SOME REDUCTION IN FORWARD SPEED. THE NEW FORECAST TRACK IS AN UPDATE OF THE PREVIOUS TRACK AND LIES IN THE CENTER OF THE TRACK GUIDANCE ENVELOPE. ANALYSES FROM CIMSS AT THE UNIVERSITY OF WISCONSIN INDICATE THAT OPHELIA IS EXPERIENCING 20-25 KT OF SHEAR DUE IN PART TO AN UPPER-LEVEL TROUGH TO THE NORTHWEST OF THE STORM. ALL OF THE DYNAMICAL MODELS INDICATE THAT MODERATE TO STRONG SHEAR IS LIKELY TO CONTINUE FOR THE NEXT 72 HOURS...AND IN RESPONSE MOST GUIDANCE SHOWS LITTLE CHANGE IN STRENGTH OR WEAKENING DURING THAT TIME. THE INTENSITY FORECAST IS MORE UNCERTAIN AFTER 72 HR. THE UPPER-LEVEL TROUGH IS FORECAST TO SLOW ITS WESTWARD MOTION AS IT MOVES NORTH OF HISPANIOLA. THIS COULD ALLOW OPHELIA TO CATCH UP WITH THE TROUGH AND ENCOUNTER STRONGER SHEAR...OR TURN NORTHWARD EAST OF THE TROUGH AND ENCOUNTER LIGHTER SHEAR. THE GFS TENDS TOWARD THE LATTER SOLUTION...WHILE THE GFDL MAKE OPHELIA A HURRICANE AFTER 96 HR. ON THE OTHER HAND...THE ECMWF SHOWS VERY STRONG UPPER-LEVEL WINDS NEAR THE STORM FROM 96-120 HR. DUE TO THE UNCERTAINTY...THERE IS NO CHANGE TO THE PREVIOUS INTENSITY FORECAST. FORECAST POSITIONS AND MAX WINDS INIT 22/0300Z 13.7N 46.2W 50 KT 60 MPH 12H 22/1200Z 14.0N 48.1W 50 KT 60 MPH 24H 23/0000Z 14.3N 50.9W 50 KT 60 MPH 36H 23/1200Z 15.2N 53.4W 50 KT 60 MPH 48H 24/0000Z 16.3N 55.8W 50 KT 60 MPH 72H 25/0000Z 18.5N 60.0W 45 KT 50 MPH 96H 26/0000Z 21.5N 64.0W 45 KT 50 MPH 120H 27/0000Z 23.5N 66.5W 45 KT 50 MPH $$ FORECASTER BEVEN |
