ZCZC MIATCDAT1 ALL TTAA00 KNHC DDHHMM TROPICAL DEPRESSION ONE DISCUSSION NUMBER 4 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 11 AM EDT SUN AUG 01 2004 THE DEPRESSION CONTINUES TO HAVE AN ILL-DEFINED AND ELONGATED CENTER WITH MULTIPLE SWIRLS. THE AIR FORCE RESERVE UNIT RECONNAISSANCE AIRCRAFT DID FIX A CENTER SOUTH OF THE PREVIOUS ADVISORY AND CLOSER TO THE DEEP CONVECTION. THIS COULD INDICATE THAT THE DEPRESSION MAY BE STARTING TO ORGANIZE A BIT...OR THEY COULD HAVE FIXED A TRANSIENT FEATURE. THE OFFICIAL CENTER POSITION IS RELOCATED A LITTLE SOUTH OF THE PREVIOUS TRACK BUT BASED ON THE OVERALL SATELLITE APPEARANCE I AM NOT GOING ALL THE WAY DOWN TO THE FIX LOCATION. THE AIRCRAFT DID REPORT FLIGHT-LEVEL WINDS OF 33 AND 36 KT...WITH A VISUAL SURFACE ESTIMATE OF 30 KT...AND THESE OBSERVATIONS ARE THE BASIS OF RAISING THE INITIAL INTENSITY TO 30 KT. THERE IS CURRENTLY VERY LITTLE WIND TO THE NORTH OR WEST OF THE CENTER. WATER VAPOR IMAGERY INDICATES STRONG UPPER-LEVEL NORTHEASTERLY FLOW AND SUBSIDENCE OVER THE NORTHERN PART OF THE DEPRESSION'S CIRCULATION...WHICH SHOULD HINDER SIGNIFICANT STRENGTHENING OF THE TROPICAL CYCLONE. HOWEVER...UPPER-LEVEL SOUTHWESTERLIES ARE HEADED TOWARD THE CYCLONE...AND AS THE FLOW TRANSITIONS THE DEPRESSION MAY FIND A BRIEFLY MORE FAVORABLE UPPER PATTERN IN 24 HOURS OR SO. THE SHIPS GUIDANCE BRINGS THE DEPRESSION TO NEAR 50 KT IN 36 HOURS...WHILE THE GFDL SHOWS LITTLE CHANGE. THE OFFICIAL FORECAST ROUGHLY SPLITS THE DIFFERENCE AND HAS THE SYSTEM AS A TROPICAL STORM VERY CLOSE TO THE COAST IN 24 HOURS. AS A RESULT...A TROPICAL STORM WARNING IS REQUIRED AT THIS TIME. LATER IN THE FORECAST PERIOD...GLOBAL MODEL GUIDANCE SHOWS THE CYCLONE MERGING WITH A LARGER EXTRATROPICAL LOW PRESSURE SYSTEM. GIVEN THE RAGGED NATURE OF THE CIRCULATION...THE INITIAL MOTION IS HARD TO DETERMINE...BUT APPEARS TO BE ESSENTIALLY STATIONARY. THE DEPRESSION IS APPROACHING A BREAK IN THE SUBTROPICAL RIDGE...SO STEERING CURRENTS ARE WEAK AND THE CYCLONE IS FORECAST TO MOVE RATHER SLOWLY AND REMAIN NEAR THE SOUTH AND NORTH CAROLINA COASTS THROUGH 36-48 HOURS. THEREAFTER...A GRADUALLY AMPLIFYING MID-LEVEL TROUGH IS LIKELY TO CARRY THE TROPICAL CYCLONE NORTHEASTWARD WITH AN INCREASE IN FORWARD SPEED. THE OFFICIAL TRACK FORECAST IS FAIRLY SIMILAR TO THE PREVIOUS ADVISORY. IF THE DEPRESSION IS IN FACT REORGANIZING FARTHER SOUTH...THEN THE CURRENT FORECAST IS LIKELY TO BE TOO FAST. FORECASTER FRANKLIN FORECAST POSITIONS AND MAX WINDS INITIAL 01/1500Z 31.9N 79.2W 30 KT 12HR VT 02/0000Z 33.0N 78.8W 30 KT 24HR VT 02/1200Z 34.1N 77.8W 35 KT 36HR VT 03/0000Z 35.1N 76.2W 40 KT 48HR VT 03/1200Z 36.5N 74.0W 40 KT 72HR VT 04/1200Z 41.0N 66.0W 40 KT 96HR VT 05/1200Z 46.0N 56.0W 40 KT...EXTRATROPICAL 120HR VT 06/1200Z...ABSORBED BY EXTRATROPICAL LOW $$ NNNN
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Page last modified: Sunday, 01-Aug-2004 15:02:11 UTC