CoconutCandy
User
Reged: Fri
Posts: 245
Loc: Beautiful Honolulu Hawaii
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Apologies for missing a few days, just a lot going on.
Not the least of which is Tropical Storm HILDA, now only 600 miles ESE of the Hawaiian Islands, and heading in our general direction, as many EastPac Cyclones are wont to do.
HILDA has persistantly and consistantly bucked a steady 15 to 20 Kts. Easterly vertical wind shear, and it was orginally thought that this shear was certain to have a significant limiting effect on the cyclone's expected peak intensity.
However, HILDA has 'nay-sayed' all the initial intensity guidance and surprised the forecasters with a slow, steady, consistant strengthening. Although most of the deep convection has, thus far, been mainly displaced in the south semi-circle, the waters are nonetheless sufficiently warm to impart the requisite energy *and* with a good outflow channel to the south, all add up to the reality of a slowly strengthening storm.
Tropical Storm HILDA Slowly Organizing Monday Afternoon.
(Note the Hawaiian Islands to the Left Side of Image.)
Instead of the original max-out at 55 kts., giving the nod to the detrimental effects of the shear, all the intensity guidance have now 'clicked-on' to the fact that HILDA has BIGGER plans despite the persistant shear, and all are now forecasting Hurricane Intensity over the next 3 or 4 days, if not sooner. 
Note that the 27C Isotherm is NE of the Hawaiian Islands in El Nino Years !!
Given the fact that the SST's are a warmish 27-28 C, plenty to support at least a Cat.1 Hurricane in and of itself, it stands to reason that *only the shear* should be a constraining factor with HILDA's bid for at least Minimal Cat. 1 Hurricane Status, if not more.
"THE SHIPS INTENSITY FORECAST SHOWS A GRADUAL RELAXATION OF THE VERTICAL SHEAR PRESENTLY OVER HILDA ..."
And since the shear has now lessened to just 15 Kts. and expected to lessen further, it's no wonder that the intensity guidance has come onboard and chimed in with a resounding 'Hurricane' within a few days time, if not sooner.
The *Actual Track* of HILDA's future path is much more problematic, and not at all certain at this time.
Although ... "HILDA WILL BE IN DEEP EASTERLY FLOW SOUTH OF A MID AND UPPER-LEVEL RIDGE EXTENDING EASTWARD FROM THE HAWAIIAN ISLANDS AND THE LOW-LEVEL SUBTROPICAL RIDGE FARTHER TO THE NORTH.
GLOBAL MODELS SHIFT THE RIDGE ALOFT TO OVER AND SOUTHWEST OF HAWAII...WHICH SHOULD TURN HILDA ON A MORE WEST-SOUTHWESTWARD COURSE FROM 24 TO 72 HOURS.
Projected Dip to the WSW Followed by Beginning of Slow(?) Recurvature
Fine and dandy. Hawaii off the hook yet again ?!? 
However! ...BEYOND 72 HOURS...THE GLOBAL MODELS HAVE DIFFERENT SOLUTIONS BUT IN GENERAL DIG AN UPPER LEVEL (trough) SOUTHWARD CLOSE TO THE HAWAIIAN ISLANDS. THE TROUGH ALOFT SHOULD WEAKEN THE SURFACE RIDGE NORTHWEST OF HILDA ... ALLOWING THE SYSTEM TO ASSUME A WEST-NORTHWEST COURSE ...
IT SHOULD BE POINTED OUT THAT (and the NGFDL) CONTINUES TO TAKE HILDA ON A MORE NORTHERN TRACK (directly towards Hawaii) AFTER 48 HOURS. IT IS *STILL TOO EARLY TO TELL* IF THIS IS A CORRECT MOVE.
If the and NGFDL have their way, Hawaii is in for a Breezy Day!
Maybe a 2nd 'Hawaiian Vacation' for the "Hurricane Hunters" ?? Certainly a situation that bears closely watching. More coming as time permits.
Please feel free to add your thoughts and comments!
Edited by CoconutCandy (Tue Aug 25 2009 09:24 AM)
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vpbob21
Weather Guru
Reged: Fri
Posts: 115
Loc: Ohio
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Hilda is looking quite anemic tonight. The convection had pretty much disappeared earlier, then there was another little burst and now that seems to be dying out. The 11 AM discussion suggested that perhaps dry air had gotten entrained into the circulation. But for whatever reason, Hilda has been weakening and is no longer forecast to reach hurricane strength.
Hilda is a small storm, and small storms are quite sensitive to adverse atmospheric conditions. It seems to be in that zone now where it could develop a big burst of convection and take off, or the thunderstorms might not refire and it might just spin down. I don't have a good feeling what might happen, but the next couple CPHC discussions should be interesting. Anyway, the weakening trend will probably ensure that it will likely be a shallow system and stay south of the islands.
Edit: Of course, almost as soon as I typed this a big burst of convection fired. We'll see if it stays persistant.
Edited by vpbob21 (Wed Aug 26 2009 01:44 AM)
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vpbob21
Weather Guru
Reged: Fri
Posts: 115
Loc: Ohio
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As is common with promising looking systems in the Central Pacific, Hilda has succumbed to the dry air that she ingested (and I'm sure a bit of shear as well). The CPHC issued the final advisory late yesterday afternoon. You can still see the low level swirl of clouds rolling along at about 15/162. Some storms are firing south and west of the COC, but no regeneration is expected.
There is another system (invest 95C) that has a Tropical Cyclone Formation Alert issued for it at about 15/177. It has a chance to be TS Neki, but will have to do so quickly as it will be crossing into the Western Pacific in about 24 hours. If it does become Neki it would be the first time since 2002 that 3 storms were named in the Central Pacific basin.
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