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#45028 (Received by flhurricane at: 10:49 PM 09.Sep.2005) TCDAT5 TROPICAL STORM NATE DISCUSSION NUMBER 18 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 11 PM EDT FRI SEP 09 2005 ALL DEEP CONVECTION ASSOCIATED WITH NATE HAS DISSIPATED AND THE CYCLONE NOW CONSISTS ONLY OF A SWIRL OF LOW-LEVEL CLOUDS. THE RAPID DEMISE OF THE CONVECTIVE STRUCTURE APPEARS TO BE ASSOCIATED WITH A COMBINATION OF VERY STRONG SHEAR...32 KT AS MEASURED BY UW-CIMSS SATELLITE WINDS...AND DRY AIR SEEN IN WATER VAPOR IMAGERY. SATELLITE CLASSIFICATIONS ARE NOW BASED ENTIRELY ON CONSTRAINTS AND CURRENTLY VARY FROM 35 KT TO 55 KT. THE INITIAL INTENSITY OF 55 KT IS BASED ON A RECENT QUICKSCAT PASS OVER THE CYCLONE AND A CIRA/NESDIS AMSU ESTIMATE OF 52 KT. NATE WILL CONTINUE TO BE WITHIN A STRONG SHEAR ENVIRONMENT AND IS CURRENTLY OVER SUB 26C SST. THUS NATE SHOULD WEAKEN AT A MODERATE RATE. NATE WILL BEGIN TO TRANSITION INTO AN EXTRATROPICAL CYCLONE AROUND 36 HOURS...BUT WILL LACK SUFFICIENT BAROCLINIC SUPPORT FOR RE-INTENSIFICATION. NOW THAT NATE IS A SHALLOW SYSTEM...IT IS BEING STEERED A LITTLE MORE EASTWARD OR APPROXIMATELY 085/21. SINCE THE RAPID DEGRADATION OF THE CONVECTION BEGINNING YESTERDAY...THE NHC MODEL GUIDANCE HAS BEEN TRENDING MORE TOWARD THE SOUTH. BASED ON THIS AND THE ALMOST DUE EASTWARD MOTION...THE OFFICIAL FORECAST IS ADJUSTED SLIGHTLY SOUTHWARD AND IS BASICALLY ON THE SOUTH SIDE OF THE TIGHTLY CLUSTERED GUIDANCE. NATE WILL BECOME ABSORBED INTO A LARGE MID-LATITUDE TROUGH OVER THE CENTRAL ATLANTIC IN ABOUT 2 TO 3 DAYS RESULTING IN A TURN TOWARD THE NORTHEAST. FORECASTER RHOME/BEVEN FORECAST POSITIONS AND MAX WINDS INITIAL 10/0300Z 34.8N 49.6W 55 KT 12HR VT 10/1200Z 35.2N 45.9W 45 KT 24HR VT 11/0000Z 36.1N 41.7W 40 KT 36HR VT 11/1200Z 38.3N 37.1W 35 KT...EXTRATROPICAL 48HR VT 12/0000Z 42.2N 33.0W 35 KT...EXTRATROPICAL 72HR VT 13/0000Z...ABSORBED |