000 WTPZ41 KNHC 170841 TCDEP1 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