Tropical Storm COSME
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TROPICAL STORM COSME DISCUSSION NUMBER 12
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP062007
200 AM PDT TUE JUL 17 2007
MICROWAVE PASSES OVER THE PAST SEVERAL HOURS SHOW THAT THE LOW-LEVEL
CENTER OF COSME IS LAGGING BEHIND ITS DEEP CONVECTION...WITH AN
EVEN GREATER SEPARATION SUGGESTED BY THE QUIKSCAT AMBIGUITIES AT
03Z. THE QUIKSCAT DATA ALSO INDICATED THAT COSME HAD WEAKENED TO A
TROPICAL STORM BY 03Z...AND IT PRESUMABLY HAS WEAKENED FURTHER
SINCE THEN. THE INITIAL INTENSITY IS LOWERED TO 55 KT FOR THIS
ADVISORY.
IN VIEW OF THE MICROWAVE DATA...AN EASTWARD RELOCATION OF THE CENTER
WAS REQUIRED...AND THE INITIAL MOTION IS NOW ESTIMATED TO BE
295/8...WHICH IS SLOWER THAN BEFORE. THE NEW FORECAST TRACK IS
ALSO A LITTLE SLOWER THAN THE PREVIOUS ONE...AND PRESUMES THAT AS
COSME MOVES OVER INCREASINGLY COOLER WATERS IT WILL HAVE A MORE
DIFFICULT TIME RESPONDING TO THE UPPER-LEVEL EASTERLIES. THE BASIC
FORECAST PHILOSOPHY HAS NOT CHANGED...HOWEVER...IN CALLING FOR
COSME TO MOVE GENERALLY TO THE WEST-NORTHWEST UNDERNEATH A STRONG
MID-LEVEL RIDGE TO THE NORTH OF THE HAWAIIAN ISLANDS. MODEL
GUIDANCE IS IN PRETTY GOOD AGREEMENT ON BRINGING COSME NEAR OR OVER
THE ISLANDS IN 4-5 DAYS.
EASTERLY SHEAR AND COOL WATERS SHOULD CAUSE COSME TO CONTINUE TO
WEAKEN OVER THE NEXT COUPLE OF DAYS. AFTER THAT...THE SHEAR IS
FORECAST TO WEAKEN...AT LEAST TEMPORARILY...AND TOWARDS THE END OF
THE PERIOD SSTS ALONG THE TRACK WILL INCREASE AGAIN.
CONSEQUENTLY...IT'S AT LEAST POSSIBLE THAT COSME COULD MAINTAIN
STORM STRENGTH THROUGH THE PERIOD. THERE IS SOME DISAGREEMENT
AMONG THE GLOBAL MODELS AS TO WHAT KIND OF UPPER FLOW WILL BE
PRESENT BY THEN...WITH THE UKMET IN PARTICULAR SHOWING INCREASING
WESTERLY SHEAR THAT WOULD PROBABLY FINISH THE CYCLONE OFF IF IT
VERIFIES. THE OFFICIAL FORECAST MAINTAINS CONTINUITY WITH THE
PREVIOUS ADVISORY AND IS CLOSE TO A BLEND OF THE GFDL...HWRF...AND
SHIPS GUIDANCE.
FORECAST POSITIONS AND MAX WINDS
INITIAL 17/0900Z 15.1N 132.7W 55 KT
12HR VT 17/1800Z 15.4N 134.1W 50 KT
24HR VT 18/0600Z 15.7N 136.1W 45 KT
36HR VT 18/1800Z 16.2N 138.6W 40 KT
48HR VT 19/0600Z 16.8N 141.4W 35 KT
72HR VT 20/0600Z 18.0N 147.0W 35 KT
96HR VT 21/0600Z 19.0N 153.0W 35 KT
120HR VT 22/0600Z 19.5N 158.5W 35 KT
$$
FORECASTER FRANKLIN
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