Tropical Storm CHRIS

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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
 
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