CoconutCandy
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Loc: Beautiful Honolulu Hawaii
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Cosme Weakens, Sputtering
Tue Jul 17 2007 07:24 PM
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Cosme weakened rather dramatically overnight, from 60 Kts. down to 40 Kts.
From the 11pm Monday (HST) NHC discussion:
"MICROWAVE PASSES OVER THE PAST SEVERAL HOURS SHOW THAT THE LOW-LEVEL CENTER OF COSME IS LAGGING BEHIND ITS DEEP CONVECTION ... AS COSME MOVES OVER INCREASINGLY COOLER WATERS IT WILL HAVE A MORE DIFFICULT TIME RESPONDING TO THE UPPER-LEVEL EASTERLIES ... MODEL GUIDANCE IS IN PRETTY GOOD AGREEMENT ON BRINGING COSME NEAR OR OVER THE HAWAIIAN ISLANDS IN 4-5 DAYS."
And from the next (5am HST) discussion:
"DURING THE LAST SIX HOURS...BOTH MICROWAVE AND CONVENTIONAL
SATELLITE IMAGERY INDICATE THAT THE CLOUD PATTERN HAS QUICKLY
DETERIORATED. TRMM AND AMSR-E OVERPASSES FROM 1018 UTC AND 1056
UTC RESPECTIVELY SHOW THAT THE LOW-LEVEL CENTER IS EXPOSED WITH THE
REMAINING DEEP CONVECTION LOCATED ABOUT 60-75 N MI TO THE WEST."
And, with the first visible images of the day, it was lowered to 35 Kts., a minimal tropical storm. As mentioned, the LLC was entirely exposed with a tight, low cloud swirl around a large clear "eye"-like feature. Apparently the cooler SST's and, especially, the easterly shear had really taken their toll.
"BOTH COOL WATERS AND EASTERLY SHEAR ARE ANTICIPATED TO CONTINUE TO
INFLUENCE THE CYCLONE'S INTENSITY...THE OFFICIAL INTENSITY FORECAST MAINTAINS COSME AS A WEAK TROPICAL STORM THROUGH 4 DAYS. HOWEVER IF THE CURRENT RAPID WEAKENING TREND CONTINUES...SOME ADDITIONAL DOWNWARD ADJUSTMENTS WILL NEED TO BE MADE."
And the latest (11am HST) discussion ...
"THE VISIBLE SATELLITE IMAGERY SHOWS THAT COSME HAS AN EXPOSED
TIGHTLY-SWIRLED CIRCULATION WITH A FEW THUNDERSTORMS CONFINED TO
THE SOUTHWESTERN QUADRANT OF THE CYCLONE ... COSME REMAINS OVER 25C WATERS AND UNDER THE INFLUENCE OF EASTERLY SHEAR ... IF THE CYCLONE SURVIVES THE NEXT THREE DAYS AND STAYS SOUTH OF THE FORECAST TRACK...THE WATERS WARM BACK UP WHICH COULD ALLOW FOR REGENERATION."
And NHC is now forecasting a downgrade to depression status by the next advisory, and holding Cosme as a depression through the forecast period.
However! In the last few frames of the animated IR loop, very deep convection, with temps of -80 and colder, has once again flared in the SW quadrant, is building and is now over-spreading the LLC. Unusual for the diurnal convective minimum of the daylight hours. (It is now early afternoon, Hawaii time, don't forget: 1pm HST, 7pm EDT)
If this convective trend continues, I hazzard to speculate that Cosme will NOT be downgraded to Depression, as forecast, but may well hold it's TS strength a while longer.
Perhaps the easterly shear is relaxing just a tad, and allowing for deep convection to re-form near and over the LLC. At any rate, it certainly will be an uphill struggle, in view of the cooler SST's mentioned above, at least in the short term.
However, as Cosme enters Hawaiian water later in the forecast period, with progressively warmer SST's, like the NHC discussion says, some regeneration and intensification is not out of the question. Time will tell.
Here's the link to the latest IR loop. Have a look for yourself.
http://weather.hawaii.edu/satellite/sata...amp;overlay=off
Will keep you posted. - Norm
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