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Tropical Storm COSME (Text)

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TROPICAL STORM COSME DISCUSSION NUMBER  17
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP062007
800 AM PDT WED JUL 18 2007
 
COSME CONTINUES TO GENERATE A STRONG CONVECTIVE CLUSTER SOUTHWEST OF
THE CENTER WITH CLOUD TOPS TO -80C.  SATELLITE INTENSITY ESTIMATES
OF 35 AND 45 KT FROM SAB AND TAFB ARE UNCHANGED FROM 6 HR AGO...AND
BASED ON THIS THE INITIAL INTENSITY WILL REMAIN 35 KT.

THE INITIAL MOTION IS 275/11.  AT THE RISK OF SOUNDING LIKE A STUCK
RECORD...THERE IS LITTLE CHANGE TO THE TRACK FORECAST THINKING...AS
A LOW/MID-LEVEL RIDGE NORTH AND NORTHWEST OF COSME REMAINS THE
PRIMARY STEERING MECHANISM.  THE LARGE-SCALE MODELS CONTINUE TO
MAINTAIN THIS RIDGE THROUGH 5 DAYS...AND THIS SHOULD KEEP THE
CYCLONE ON A WEST TO WEST-NORTHWESTWARD TRACK AS SHOWN BY ALL
GUIDANCE.  THERE IS SOME SPREAD BETWEEN THE REGIONAL GFDL AND HWRF
MODELS...WHICH CALL MORE A MORE NORTHERLY TRACK CLOSER TO HAWAII...
AND THE GLOBAL MODELS...WHICH CALL FOR A MORE SOUTHERLY TRACK.  THE
NEW TRACK FORECAST IS SIMILAR TO THE PREVIOUS TRACK AND IN BETWEEN
THE GLOBAL AND REGIONAL MODELS.
 
THE INTENSITY FORECAST IS STILL SOMEWHAT PROBLEMATIC.  IN THE SHORT
TERM...COSME SHOULD REACH GRADUALLY INCREASING SEA SURFACE
TEMPERATURES IN ABOUT 36 HR IN A LIGHT SHEAR ENVIRONMENT.  THIS
SUGGEST THE POSSIBILITY OF SOME STRENGTHENING.  HOWEVER...THE
CURRENT GUIDANCE SUGGESTS A SLOW WEAKENING THROUGH 72 HR.  AFTER 72
HR...COSME SHOULD REACH SIGNIFICANTLY WARMER WATER AND QUITE
POSSIBLY SIGNIFICANT VERTICAL WIND SHEAR...AS THE NOGAPS...UKMET...
AND ECMWF NOW SHOW STRONGER UPPER-LEVEL WESTERLIES NEAR THE
FORECAST TRACK THAN THE PREVIOUS RUNS.  THE GFS...WHICH PROVIDES
THE SHEAR VALUES FOR THE SHIPS MODEL...FORECASTS A LESS HOSTILE
ENVIRONMENT.  GIVEN THE UNCERTAINTY...THE NEW INTENSITY FORECAST
WILL BE THE SAME AS THE FORECAST FROM THE PREVIOUS PACKAGE. 
HOWEVER...THIS IS A LOW CONFIDENCE FORECAST AFTER 72 HR...AS BY
120 HR COSME COULD BE RE-INTENSIFYING OR COMPLETELY DISSIPATED
DEPENDING ON HOW MUCH SHEAR IT ENCOUNTERS.

COSME WILL BE VERY CLOSE TO 140W BY 18Z...AND THE CENTRAL PACIFIC
HURRICANE CENTER WILL LIKELY ASSUME RESPONSIBILITY AFTER THE NEXT
ADVISORY.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      18/1500Z 15.3N 138.9W    35 KT
 12HR VT     19/0000Z 15.4N 140.7W    35 KT
 24HR VT     19/1200Z 15.9N 143.3W    30 KT
 36HR VT     20/0000Z 16.4N 146.1W    30 KT
 48HR VT     20/1200Z 16.8N 149.2W    30 KT
 72HR VT     21/1200Z 17.5N 155.5W    30 KT
 96HR VT     22/1200Z 18.0N 161.0W    25 KT
120HR VT     23/1200Z 18.0N 166.0W    25 KT
 
$$
FORECASTER BEVEN
 
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