|
Show Selection: |
| #110687 (Received by flhurricane at: 4:40 PM 13.Sep.2006) TCDAT3 TROPICAL DEPRESSION EIGHT DISCUSSION NUMBER 6 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082006 500 PM AST WED SEP 13 2006 SATELLITE IMAGERY THIS AFTERNOON INDICATES THAT TROPICAL DEPRESSION EIGHT IS SLOWLY BECOMING BETTER ORGANIZED. A CONVECTIVE BAND HAS FORMED IN THE NORTHWESTERN QUADRANT...ALTHOUGH THE BAND IS MORE THAN 100 N MI FROM THE CENTER IN MOST AREAS. THE OVERALL CIRCULATION IS MORE CIRCULAR AND BETTER DEFINED THAN 6 HR AGO. SATELLITE INTENSITY ESTIMATES ARE 35 KT FROM TAFB...AND 30 KT FROM SAB AND AFWA. THE INITIAL INTENSITY REMAINS 30 KT. IT SHOULD BE NOTED THAT THE INITIAL POSITION IS SOUTH OF THE SATELLITE FIXES... AND THE CENTER MAY BE TRYING TO RE-FORM FARTHER NORTH CLOSER TO THE CONVECTION. THE INITIAL MOTION IS A SOMEWHAT UNCERTAIN 275/16...WITH A POSSIBLE FASTER MOTION OVER THE PAST FEW HOURS. THE DEPRESSION REMAINS SOUTH OF A DEEP-LAYER RIDGE OVER THE EASTERN ATLANTIC...WHICH SHOULD KEEP THE SYSTEM MOVING QUICKLY WESTWARD FOR 24 HR OR SO. AFTER THAT...THE LARGE-SCALE MODELS FORECAST THE CYCLONE TO GRADUALLY TURN WEST-NORTHWESTWARD AND THEN NORTHWESTWARD TOWARD A WEAKNESS IN THE RIDGE NORTHEAST OF THE LESSER ANTILLES. THE UKMET AND THE NOGAPS FORECAST MORE RIDGING NORTH OF THE DEPRESSION THAN THEIR PREVIOUS RUNS...AND THEY TURN THE CYCLONE TO SOMEWHAT TO THE LEFT AFTER 96 HR. THIS IS REFLECTED IN THE NEW FORECAST TRACK. THE CANADIAN REMAINS A LEFT OUTLIER....ALTHOUGH IT HAS SHIFTED TO THE RIGHT OF ITS PREVIOUS TRACK. THE GFS...GFDL...AND ECMWF ARE SIMILAR TO THEIR PREVIOUS RUNS...WITH THE GFDL FASTER THAN THE OTHER MODELS AFTER 72 HR. THE NEW FORECAST TRACK IS FASTER THAN THE PREVIOUS TRACK DURING THE FIRST 24 HR...THEN IS SLOWER THAN THE PREVIOUS TRACK AFTER 72 HR. IT LIES NEAR THE SOUTH EDGE OF THE MAIN CLUSTER OF GUIDANCE. THE BROAD STRUCTURE SUGGESTS THAT SHORT-TERM INTENSIFICATION SHOULD BE SLOW. THIS IS REFLECTED IN THE FIRST 24 HR OF THE INTENSITY FORECAST. THE SYSTEM SHOULD THEN STRENGTHEN AT A FASTER RATE IN A LIGHT VERTICAL SHEAR ENVIRONMENT...AND IT IS FORECAST TO BECOME A HURRICANE IN ABOUT 72 HR. THE INTENSITY FORECAST IS IN BEST AGREEMENT WITH THE GFDL. THERE REMAIN TWO COMPLICATING FACTORS IN THE INTENSITY FORECAST. THE FIRST IS DRY AIR PRESENT NORTH AND WEST OF THE CYCLONE. HOW MUCH OF THIS AIR WILL BE ENTRAINED INTO THE SYSTEM IS UNCLEAR. THE SECOND IS AN UPPER-LEVEL TROUGH FORECAST BY THE LARGE-SCALE MODELS TO THE NORTH OR NORTHEAST OF THE LESSER ANTILLES BY 96-120 HR. WHILE THE MODELS AGREE THE TROUGH WILL EXIST...THEY DO NOT AGREE ON THE LOCATION OR ON THE POSSIBLE IMPACT TO THE CYCLONE. FORECAST POSITIONS AND MAX WINDS INITIAL 13/2100Z 12.7N 30.7W 30 KT 12HR VT 14/0600Z 12.9N 33.3W 35 KT 24HR VT 14/1800Z 13.6N 36.4W 40 KT 36HR VT 15/0600Z 14.7N 39.0W 50 KT 48HR VT 15/1800Z 16.1N 41.1W 60 KT 72HR VT 16/1800Z 18.5N 44.0W 70 KT 96HR VT 17/1800Z 20.5N 46.5W 80 KT 120HR VT 18/1800Z 22.0N 49.5W 85 KT $$ FORECASTER BEVEN |
