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#105540 (Received by flhurricane at: 5:00 PM 22.Aug.2006) TCDAT4 TROPICAL DEPRESSION FOUR DISCUSSION NUMBER 5 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL042006 500 PM EDT TUE AUG 22 2006 DESPITE SOME INCREASE OF CONVECTION NEAR THE CENTER THIS AFTERNOON...THERE IS LIMITED BANDING AND DVORAK INTENSITY ESTIMATES FROM TAFB AND SAB REMAIN AT 30 KT. CONSEQUENTLY THE SYSTEM WILL NOT BE UPGRADED AT THIS TIME. HOWEVER...WITH CONVECTION ON THE INCREASE THE CLASSIFICATIONS SHOULD SUPPORT TROPICAL STORM STRENGTH VERY SOON. WHILE THE OUTFLOW PATTERN HAS BEEN IMPROVING TODAY AND THE SHEAR IS FAIRLY LOW...THE CYCLONE WILL BE MOVING OVER SLIGHTLY COOLER WATERS AND A MORE STABLE BOUNDARY LAYER FLOW...SO I AM ANTICIPATING ONLY SLOW DEVELOPMENT OVER THE NEXT COUPLE OF DAYS. AFTER THAT...WATERS WARM BUT SOME OF THE GLOBAL MODELS SUGGEST AN INCREASE IN SOUTHERLY SHEAR ASSOCIATED WITH AN UPPER-LEVEL LOW IN THE CENTRAL ATLANTIC. BOTH THE SHIPS AND GFDL MODELS HAVE BACKED OFF SLIGHTLY WITH THEIR INTENSITY FORECASTS AND THE OFFICIAL FORECAST IS ALSO NUDGED DOWN. THE INITIAL MOTION IS 300/16...OR ABOUT 15 DEGREES TO THE RIGHT OF THIS TIME YESTERDAY. RECENT MICROWAVE PASSES SUGGEST A BETTER CO-LOCATION OF THE MID AND LOW-LEVEL CENTERS. THERE HAS BEEN SIGNIFICANT CONVERGENCE IN HOW THE GLOBAL MODELS HANDLE THE DEPRESSION...WITH THE 12Z RUNS OF THE UKMET AND ECMWF NOW MAINTAINING THE SYSTEM AND SHIFTING THEIR TRACKS TO THE RIGHT. THEY ARE NOW IN GOOD AGREEMENT WITH THE GFS AND ALSO WITH THE GFDL THROUGH ABOUT 72 HOURS. THERE HAS BEEN LITTLE CHANGE TO THE SYNOPTIC SITUATION...WITH ALL THE GUIDANCE INDICATING AN EASTWARD SHIFT OF THE SUBTROPICAL RIDGE AND TROUGHING DEVELOPING OVER THE CENTRAL ATLANTIC. THE OFFICIAL FORECAST HAS BEEN SHIFTED SLIGHTLY TO THE RIGHT OF THE PREVIOUS TRACK AND IS IN BEST AGREEMENT WITH THE GFS AND ECMWF. FORECAST POSITIONS AND MAX WINDS INITIAL 22/2100Z 14.5N 27.5W 30 KT 12HR VT 23/0600Z 15.7N 29.7W 35 KT 24HR VT 23/1800Z 17.2N 32.4W 40 KT 36HR VT 24/0600Z 18.8N 35.2W 40 KT 48HR VT 24/1800Z 20.1N 38.0W 45 KT 72HR VT 25/1800Z 23.0N 44.0W 50 KT 96HR VT 26/1800Z 27.0N 49.0W 55 KT 120HR VT 27/1800Z 30.0N 53.0W 60 KT |