ZCZC MIATCDAT1 ALL TTAA00 KNHC DDHHMM TROPICAL DEPRESSION SIX DISCUSSION NUMBER 6 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 11 PM EDT SUN JUL 20 2003 TROPICAL DEPRESSION SIX IS A LITTLE BETTER ORGANIZED TONIGHT THAN 24 HR AGO. WHILE THE LOW-LEVEL CENTER IS STILL POORLY DEFINED... THERE HAS BEEN SOME INCREASE IN THE CONVECTIVE CURVATURE NEAR THE CENTER. SATELLITE INTENSITY ESTIMATES ARE 35 KT FROM TAFB...AND 30 KT FROM SAB AND AFWA. BASED ON THIS AND RECENT WARMING OF THE CLOUD TOPS...THE SYSTEM WILL REMAIN A 30 KT DEPRESSION AT THIS TIME. THE INITIAL MOTION REMAINS 275/20. THE DEPRESSION REMAINS ON THE SOUTH SIDE OF THE STRONG ANTICYCLONE OVER THE CENTRAL ATLANTIC... AND SHOULD REMAIN THERE FOR 72 HR OR SO. THIS SHOULD CONTINUE A BRISK WESTWARD OR WEST-NORTHWESTWARD MOTION. ALL GUIDANCE AGREES WITH THIS...AS WILL THE OFFICIAL FORECAST. AFTER 72 HR...THE FORECAST GETS TRICKIER AS THE CYCLONE APPROACHES A DE-AMPLIFYING DEEP-LAYER TROUGH OVER THE EASTERN UNITED STATES. WHILE DETAILS DIFFER...THE GFS AND THE NOGAPS BUILD A PORTION OF THE ATLANTIC RIDGE WESTWARD TOWARD FLORIDA. IF THIS OCCURS...THE CYCLONE WOULD LIKELY CONTINUE WEST-NORTHWEST AT A SLOWER SPEED. THIS SCENARIO IS CURRENTLY SUPPORTED BY MOST GUIDANCE...AND THE OFFICIAL FORECAST GOES ALONG WITH IT. AN ALTERNATE SCENARIO COMES FROM THE UKMET... WHICH KEEPS ENOUGH OF A WEAKNESS TO TURN THE CYCLONE NORTHWESTWARD THOUGH THE BAHAMAS AND JUST EAST OF FLORIDA. THE UKMET IS CURRENTLY A RIGHT OUTLIER...BUT CANNOT BE RULED OUT YET. THE INTENSITY FORECAST IS PROBLEMATIC. FIRST...THE CYCLONE IS POORLY ORGANIZED. SECOND...WHILE LARGE-SCALE MODELS BUILD AN UPPER-LEVEL ANTICYCLONE WESTWARD TO PROVIDE A PATTERN FAVORABLE FOR DEVELOPMENT...THE MODELS CONSISTENTLY OVERDID SUCH FORECASTS DURING CLAUDETTE...AND CURRENT SATELLITE IMAGERY INDEED SHOWS THE CYCLONE GETTING CLOSER TO SOUTHWESTERLY AND SOUTHERLY UPPER-LEVEL FLOW WHICH COULD SLOW OR HALT DEVELOPMENT. THIRD...AFTER 48 HR THE SYSTEM WILL BE NEAR OR OVER HISPANIOLA AND CUBA...AND THE DIFFERENCE BETWEEN NEAR AND OVER COULD HAVE HUGE IMPACTS ON THE INTENSITY. FINALLY...NONE OF THE INTENSITY GUIDANCE FORECASTS MUCH DEVELOPMENT. THE OFFICIAL INTENSITY FORECAST WILL COMPROMISE BETWEEN THESE POSSIBILITIES BY FORECASTING SLOW STRENGTHENING FOR 48-72 HR...THEN LITTLE CHANGE UNTIL THE CYCLONE REACHES THE GULF OF MEXICO. HOWEVER...THIS IS A LOW CONFIDENCE INTENSITY FORECAST. FORECASTER BEVEN FORECAST POSITIONS AND MAX WINDS INITIAL 21/0300Z 13.7N 54.6W 30 KT 12HR VT 21/1200Z 14.1N 57.6W 35 KT 24HR VT 22/0000Z 15.0N 61.5W 40 KT 36HR VT 22/1200Z 16.1N 65.4W 45 KT 48HR VT 23/0000Z 17.2N 69.0W 50 KT 72HR VT 24/0000Z 19.5N 76.0W 55 KT 96HR VT 25/0000Z 22.0N 81.0W 55 KT 120HR VT 26/0000Z 24.5N 85.5W 60 KT NNNN
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Page last modified: Monday, 07-Feb-2005 16:49:56 UTC