Tropical Storm Cosme was upgraded to Hurricane at 11am HST, after steadily strengthening overnight and during the morning hours.

From NHC's latest (11am HST) forecast discussion:

"THE SATELLITE PRESENTATION HAS IMPROVED AND COSME HAS A SMALL EYE WITH A WELL-DEFINED CURVED BAND WRAPPING FULLY AROUND THE CENTER. DVORAK ESTIMATES FROM BOTH TAFB AND SAB ARE 65 KT. THE INITIAL INTENSITY HAS BEEN RAISED TO 65 KT."

The 'pseudo-eyewall replacement cycle' discussed in my last post did occur, and for a few hours a small eye was observed on visible satellite imagery. Since then, the eye has become cloud filled and/or obscured by cirrus debris.

However, IR imagery continues to show deep convection forming near the center, so it is difficult to say whether Cosme has peaked in intensity or is still strengthening just a tad more, per NHC's forecast peak of 70 Kts. And it continues to exhibit excellent outflow in nearly all quadrants, with very light shear prevailing for the foreseeable future.

The next advisory in a couple hours will reveal Cosmes' strength following the visible eye event. I suspect it is still maintaining a closed eyewall feature, shown nicely in a TRMM microwave overpass at 9:30 this morning HST. (See attachment.)

If Cosme hasn't peaked yet, it is expected to do so soon. From visible satellite loops it's apparent that Cosmes' circulation is beginning to entrain more and more of the stable stratocumulus cloud field to its NW.

More importantly, the projected track will take Cosme over progressively cooler SST temps in the next 24-36 hours. It will be crossing over several isotherms in quick succession during that time frame, as the thermal gradient is rather tight in this area.

"...COSME'S INTENSITY COULD BE PEAKING...SINCE WATER TEMPERATURES ARE
ALREADY BELOW 26C AND ARE EXPECTED TO DECREASE FURTHER ALONG THE
PROJECTED TRACK. THE OFFICIAL INTENSITY FORECAST ALLOWS FOR SOME
STRENGTHENING IN THE NEXT 12 HOURS...BUT THEN GRADUALLY WEAKENS THE
CYCLONE THROUGH DAY FIVE...AS A RESULT OF THE COOLER WATERS AND A
MORE STABLE ENVIRONMENT."

The good / bad news, depending on your perspective, is that Cosme is now expected to maintain its' identity longer than earlier forecast, and the latest track shows a minimal tropical storm with its' center of circulation passing over or just barely south of the southern tip of the Big Island of Hawaii in the early morning hours this Saturday.

[image] http://www.nhc.noaa.gov/refresh/graphics_ep1+shtml/203532.shtml?5day?large#contents [/image]

(In case the above image doesn't display, here's the direct link:)

http://www.nhc.noaa.gov/refresh/graphics_ep1+shtml/203532.shtml?5day?large#contents

While it is very likely that Cosme will bring much-needed rains to the Big island and perhaps Maui,

it will also bring in tons of humidity over the state as it passes by during the weekend, making for several days of very muggy and highly uncomfortable weather.

Let's just hope it does weaken as quickly as expected; while the Big Island certainly needs a good soaking, it surely doesn't need any kind of severe wind event to contend with.

And as I was mentioning in my previous post ... and from NHC's last discussion ...

"ONE BIT OF TRIVIA...ONLY FOUR OTHER EAST PACIFIC HURRICANE SEASONS
HAVE HAD THEIR FIRST HURRICANE FORM LATER THAN COSME."

... and the fact that Cosme is the first *hurricane* to form in the Northern Hemisphere 2007 season. Rather unusual.

More coming after the 5pm HST advisory from the NHC ...