Tropical Storm COSME

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TROPICAL STORM COSME DISCUSSION NUMBER  15
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP062007
800 PM PDT TUE JUL 17 2007
 
WHILE COSME CONTINUES TO UNDERGO EASTERLY VERTICAL WIND SHEAR...
CONVECTION HAS MADE A COMEBACK THIS EVENING WITH TOPS TO -80C IN A
CLUSTER TO THE SOUTHWEST OF THE CENTER.  SATELLITE INTENSITY
ESTIMATES ARE 45 KT FROM TAFB AND SAB.  HOWEVER...THE INITIAL
INTENSITY WILL BE HELD AT 35 KT UNTIL THE CONVECTION SHOWS SOME
PERSISTENCE.  AN UPCOMING QUIKSCAT OVERPASS MAY PROVIDE BETTER
INFORMATION ON THE ACTUAL INTENSITY OF COSME.

THE INITIAL MOTION IS 275/11.  A LOW/MID-LEVEL RIDGE NORTH AND
NORTHWEST OF COSME REMAINS THE PRIMARY STEERING MECHANISM.  THE
LARGE-SCALE MODELS CONTINUE TO MAINTAIN THE RIDGE FOR THE NEXT 5
DAYS...WHICH SHOULD STEER THE CYCLONE WEST-NORTHWESTWARD TO
WESTWARD.  THE GFS...NOGAPS...UKMET...AND ECMWF NOW CALL MORE A
MORE WESTERLY TRACK THAN THEIR PREVIOUS RUNS...WHILE THE GFDL CALLS
FOR A TRACK THROUGH THE HAWAIIAN ISLANDS.  IN DEFERENCE TO THE
GLOBAL MODELS...THE NEW FORECAST TRACK IS SHIFTED SOMEWHAT TO THE
SOUTH.  THE NEW TRACK IS IN BEST AGREEMENT WITH THE NOGAPS AND THE
CCON CONSENSUS MODEL.
 
THE INTENSITY FORECAST IS PROBLEMATIC.  THE LARGE-SCALE MODELS
FORECAST THE SHEAR TO DIMINISH DURING THE NEXT 24 HOURS...AND AFTER
THAT TIME THE CYCLONE WILL BE MOVING OVER GRADUALLY INCREASING SEA
SURFACE TEMPERATURES.  IF THE CURRENT CONVECTION PERSISTS...THIS
COULD ALLOW COSME TO MAINTAIN ITSELF OR EVEN SLIGHTLY RE-STRENGTHEN. 
ON THE OTHER HAND...THE ONLY MODEL THAT FOLLOWS THIS SCENARIO AT
THE MOMENT IS THE GFDL.  AFTER 72 HR...AN UPPER-LEVEL LOW IS
FORECAST TO FORM NORTH OF THE FORECAST TRACK... WHICH COULD CAUSE
WESTERLY SHEAR.  HOWEVER...THE STRONGEST SHEAR IS NORTH OF THE
FORECAST TRACK...AND ANY MOTION SOUTH OF THE FORECAST TRACK WOULD
ALLOW COSME TO MISS THAT AREA.  GIVEN THE UNCERTAINTY...THE
LOW-CONFIDENCE INTENSITY FORECAST WILL BE SIMILAR TO THE PREVIOUS
ADVISORY...ASSUMING THAT THE CURRENT CONVECTION WILL NOT PERSIST
AND CALLING FOR COSME TO GRADUALLY WEAKEN AND DISSIPATE DURING THE
NEXT 4-5 DAYS.  THIS IN BEST AGREEMENT WITH THE SHIPS MODEL.

 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      18/0300Z 15.1N 136.6W    35 KT
 12HR VT     18/1200Z 15.2N 138.4W    35 KT
 24HR VT     19/0000Z 15.6N 140.9W    30 KT
 36HR VT     19/1200Z 16.2N 143.6W    30 KT
 48HR VT     20/0000Z 16.7N 146.6W    30 KT
 72HR VT     21/0000Z 17.5N 152.5W    25 KT
 96HR VT     22/0000Z 18.0N 157.0W    25 KT...DISSIPATING
120HR VT     23/0000Z 18.5N 161.5W    20 KT...REMNANT LOW
 
$$
FORECASTER BEVEN
 
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