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| #536401 (Received by flhurricane at: 4:44 PM 23.Aug.2012) TCDAT5 TROPICAL STORM JOYCE DISCUSSION NUMBER 6 NWS NATIONAL HURRICANE CENTER MIAMI FL AL102012 500 PM AST THU AUG 23 2012 SATELLITE DATA INDICATE THAT THE CENTER OF JOYCE HAS UNEXPECTEDLY BECOME EXPOSED. THE DEEP CONVECTION...WHICH WAS EARLIER THOUGHT TO BE PARTIALLY COVERING THE CENTER...HAS BEEN CARRIED FAR TO THE NORTHWEST ALONG WITH A STRONG MID-LEVEL CYCLONIC CIRCULATION... LEAVING THE LOW-LEVEL CENTER BEHIND. AN 1816 UTC SSMI OVERPASS CONFIRMED THIS STARK DECOUPLING...WHICH APPEARS TO HAVE RESULTED FROM A COMBINATION OF SOUTH-SOUTHEASTERLY SHEAR AND DRY AIR. ALTHOUGH DVORAK T-NUMBERS HAVE DECREASED AS A RESULT OF THE DECREASE IN ORGANIZATION...IT IS ASSUMED THAT TROPICAL-STORM-FORCE WINDS ARE STILL OCCURRING IN THE CONVECTION WELL TO THE NORTH IN ASSOCIATION WITH THE MID-LEVEL CYCLONIC CIRCULATION. THE WIND RADII HAVE TEMPORARILY BEEN ADJUSTED TO REFLECT THIS DISPLACEMENT. THE INITIAL MOTION ESTIMATE IS A HIGHLY UNCERTAIN 300/12 SINCE THE CENTER POSITION WAS NOT WELL KNOWN EARLIER. JOYCE IS EXPECTED TO BE STEERED WEST-NORTHWESTWARD TO NORTHWESTWARD FOR THE NEXT FEW DAYS AROUND THE SOUTH SIDE OF A SUBTROPICAL RIDGE OVER THE CENTRAL ATLANTIC. A TURN TOWARD THE NORTH AND THEN NORTHEAST SHOULD OCCUR IN ABOUT 4-5 DAYS AS JOYCE ENCOUNTERS A BREAK IN THE RIDGE OVER THE WESTERN ATLANTIC AND RECURVES INTO A STRONG BAND OF WESTERLIES TO THE NORTH. THE NHC TRACK FORECAST HAS BEEN SHIFTED TO THE RIGHT IN THE FIRST 48-72 HOURS TO ACCOUNT FOR THE POSSIBLE REFORMATION OF JOYCE TO THE NORTH. THE REMAINDER OF THE FORECAST IS SIMILAR TO THE PREVIOUS ONE AND IS CLOSE TO A BLEND OF THE ECMWF/GFS...WHICH SHOWED A DEEPER REPRESENTATION OF THE CYCLONE. ONE OF TWO OPTIONS SEEMS PLAUSIBLE IN THE SHORT TERM WITH REGARD TO THE INTENSITY FORECAST. A NEW LOW-LEVEL CENTER COULD FORM IN ASSOCIATION WITH THE MID-LEVEL CYCLONIC CENTER AND BECOME DOMINANT. THE OTHER POSSIBILITY IS THAT NO NEW CENTER WILL FORM AND JOYCE WILL DISSIPATE. ASSUMING THAT JOYCE SURVIVES DURING THE NEXT DAY OR TWO...THE PROSPECT FOR INTENSIFICATION SEEMS UNLIKELY FOR THE NEXT 2-3 DAYS. THE CONTINUED PROXIMITY OF A MID- TO UPPER-LEVEL TROUGH...COUPLED WITH THE EFFECTS OF DRY AIR...SHOULD INHIBIT ANY SIGNIFICANT STRENGTHENING. LATER IN THE FORECAST PERIOD...GLOBAL MODELS CONTINUE TO ADVERTISE SOME CHANCE OF JOYCE INTENSIFYING AROUND THE TIME IT RECURVES. THE NEW NHC INTENSITY FORECAST HAS BEEN REDUCED DURING THE FIRST COUPLE OF DAYS AND MODIFIED UPWARD ON DAYS 4-5. FORECAST POSITIONS AND MAX WINDS INIT 23/2100Z 15.9N 42.5W 35 KT 40 MPH 12H 24/0600Z 17.1N 45.1W 35 KT 40 MPH 24H 24/1800Z 18.5N 47.9W 35 KT 40 MPH 36H 25/0600Z 20.0N 50.8W 35 KT 40 MPH 48H 25/1800Z 22.1N 54.4W 35 KT 40 MPH 72H 26/1800Z 26.3N 60.4W 45 KT 50 MPH 96H 27/1800Z 30.8N 63.0W 50 KT 60 MPH 120H 28/1800Z 34.5N 60.4W 55 KT 65 MPH $$ FORECASTER KIMBERLAIN |
