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| #4743 (Received by flhurricane at: 11:07 AM 13.Aug.2004) TCDAT4 TROPICAL DEPRESSION FOUR DISCUSSION NUMBER 1 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 11 AM EDT FRI AUG 13 2004 CONVENTIONAL AND MICROWAVE SATELLITE IMAGERY INDICATE THAT THE TROPICAL DISTURBANCE LOCATED ABOUT 240 NMI SOUTH-SOUTHEAST OF THE CAPE VERDE ISLANDS HAS BECOME MUCH BETTER ORGANIZED THIS MORNING. THE SYSTEM IS BEING UPGRADED TO TROPICAL DEPRESSION FOUR BASED ON A CONSENSUS DVORAK SATELLITE INTENSITY ESTIMATE OF T2.0...OR 30 KT... FROM TAFB AND SAB...AND IMPROVED BANDING FEATURES. UPPER-LEVEL OUTFLOW IS GOOD IN THE SOUTHERN SEMICIRCLE AND FAIR ELSEWHERE. THE INITIAL MOTION ESTIMATE IS 280/13. LOCATING THE EXACT CENTER IS DIFFICULT AT THIS TIME DUE TO CONTINUED REORGANIZATION OF THE CENTRAL DEEP CONVECTION. HOWEVER...THE GENERAL MOTION SHOULD BE WESTWARD FOR THE NEXT 24 TO 36 HOURS AS THE CYCLONE IS STEERED BY THE DEEP EASTERLY FLOW TO NORTH. BY 48 HOURS...ALL THE GLOBAL MODELS AGREE ON A MID-LEVEL TROUGH DIGGING SOUTHEASTWARD BETWEEN 35-40W LONGITUDE...WHICH SHOULD WEAKEN THE SUBTROPICAL RIDGE. A SMALL POLEWARD STAIR-STEP IN THE TRACK MAY OCCUR AT THAT TIME... AFTER WHICH A RETURN TO A MORE WESTWARD MOTION IS EXPECTED AS THE TROUGH LIFTS OUT TO THE NORTHEAST OF THE CYCLONE. BASED ON THE FORECAST TRACK...THE DEPRESSION IS EXPECTED TO MOVE NORTH OF THE WARMEST WATER IN 36 TO 48 HOURS. THIS WILL ALSO PLACE THE SYSTEM DEEPER INTO THE COOLER AND MORE STABLE TRADE WIND FLOW THAT EXISTS EAST OF 50W LONGITUDE. AS SUCH...ONLY MODEST INTENSIFICATION IS EXPECTED THROUGHOUT THE FORECAST PERIOD. HOWEVER...IF THE CYCLONE TAKES A MORE SOUTHERLY TRACK AND STAYS OVER WARMER WATER...THEN IT COULD BECOME A HURRICANE BY 72 HOURS. THE INTENSITY FORECAST IS CLOSE TO THE SHIPS INTENSITY MODEL. FORECASTER STEWART FORECAST POSITIONS AND MAX WINDS INITIAL 13/1500Z 12.2N 22.7W 30 KT 12HR VT 14/0000Z 12.4N 24.5W 35 KT 24HR VT 14/1200Z 12.8N 27.0W 40 KT 36HR VT 15/0000Z 13.3N 29.5W 45 KT 48HR VT 15/1200Z 14.0N 32.0W 50 KT 72HR VT 16/1200Z 15.5N 36.5W 55 KT 96HR VT 17/1200Z 16.5N 41.0W 60 KT 120HR VT 18/1200Z 17.0N 46.5W 60 KT |
