ZCZC MIATCDAT3 ALL TTAA00 KNHC DDHHMM TROPICAL STORM CHRIS DISCUSSION NUMBER 2 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL032006 500 AM EDT TUE AUG 01 2006 CONVENTIONAL AND MICROWAVE SATELLITE DATA THIS MORNING ESTIMATE THAT TROPICAL DEPRESSION THREE HAS STRENGTHENED INTO TROPICAL STORM CHRIS...WHILE ALSO DECREASING ITS FORWARD SPEED. THE INITIAL INTENSITY OF 35 KT IS BASED ON A SATELLITE INTENSITY OF T2.5/35 KT FROM TAFB...A DATA T-NUMBER OF T2.5 FROM SAB...AND TWO CONSECUTIVE AMSU INTENSITY ESTIMATES 35-36 KT. SINCE THE 00Z SATELLITE INTENSITY ESTIMATES...DEEP CONVECTION HAS INCREASED IN BOTH DEPTH AND ORGANIZATION AROUND THE LOW-LEVEL CENTER. THE INITIAL MOTION ESTIMATE IS 295/08 KT...BASED MAINLY ON MICROWAVE SATELLITE FIX POSITIONS OVER THE PAST 12 HOURS. NOW THAT CHRIS HAS BECOME A MORE VERTICALLY DEEP SYSTEM...THE CYCLONE IS EXPECTED TO BE STEERED IN A GENERAL WEST-NORTHWESTWARD MOTION AROUND THE SOUTHERN PERIPHERY OF THE LARGE-SCALE SUBTROPICAL RIDGE THAT IS LOCATED NORTH OF CHRIS AND WHICH EXTENDS WESTWARD ACROSS THE SOUTHEASTERN U.S. AND INTO THE U.S. SOUTHERN PLAINS. THE FUTURE TRACK OF CHRIS HINGES HEAVILY UPON JUST HOW STRONG THE CYCLONE BECOMES. MY FEELING NOW IS THAT CHRIS SHOULD REMAIN A SIGNIFICANT TROPICAL CYCLONE THROUGHOUT THE 120-H FORECAST PERIOD...WHICH IS IN CONTRAST TO ALL OF THE GLOBAL MODELS AND THE GFDL MODEL. BY 72 HOURS...CHRIS IS FORECAST TO WEAKEN CONSIDERABLY AND BE DRIVEN WESTWARD OVER OR SOUTH OF HISPANIOLA...OR DISSIPATE COMPLETELY. PART OF THE RAPID DISSIPATION FORECAST BY THE MODELS MAY BE DUE TO POOR INITIALIZATION. A STRONGER AND SOMEWHAT LARGER CYCLONE MAY RESULT IN A DIFFERENT PROGNOSIS OF THE 06Z MODEL RUNS. THE OFFICIAL FORECAST TRACK IS SIMILAR TO THE PREVIOUS TRACK...ALTHOUGH IT NOW EXTENDS OUT TO 120 HOURS...AND IS A LITTLE NORTH OF AND SLOWER THAN THE GLOBAL MODEL CONSENSUS. THE VERTICAL SHEAR THAT HAS BEEN AFFECTING CHRIS IS FORECAST BY ALL THE MODELS TO WEAKEN SOMEWHAT...WHICH WOULD FAVOR AT LEAST SOME SLOW SLOW STRENGTHENING. THE MAIN DILEMMA IS JUST HOW STRONG CHRIS WILL BECOME. CHRIS IS FORECAST TO PASS BETWEEN TWO MID- TO UPPER- LEVEL LOWS CURRENTLY LOCATED EAST OF THE BAHAMAS AND NORTHEAST OF THE CYCLONE. ALL OF THE GLOBAL MODELS GRADUALLY WEAKEN THE TWO LOWS AND THEN MOVE THEM IN TANDEM WESTWARD AFTER 72 HOURS... WITH CHRIS LIKELY WEDGED IN BETWEEN. THIS TYPE OF PATTERN WOULD NORMALLY FAVOR A LOW SHEAR PATTERN THAT WOULD BE CONDUCIVE FOR MORE STRENGTHENING THAN IS CURRENTLY FORECAST...BUT ONLY IF CHRIS REMAINS EXACTLY BETWEEN THE TWO LOWS. THE OFFICIAL FORECAST TRACK IS A REVERSAL OF THE PREVIOUS FORECAST AFTER 48 HOURS...AND IS SIMILAR TO THE SHIPS AND GFDL MODELS. FORECAST POSITIONS AND MAX WINDS INITIAL 01/0900Z 16.6N 59.2W 35 KT 12HR VT 01/1800Z 17.3N 61.0W 40 KT 24HR VT 02/0600Z 18.2N 63.2W 45 KT 36HR VT 02/1800Z 19.0N 65.3W 50 KT 48HR VT 03/0600Z 19.9N 67.5W 50 KT 72HR VT 04/0600Z 21.3N 71.2W 50 KT 96HR VT 05/0600Z 22.5N 74.5W 55 KT 120HR VT 06/0600Z 24.0N 77.5W 55 KT $$ FORECASTER STEWART NNNN
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Page last modified: Monday, 11-Sep-2006 11:28:34 UTC