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Archives 2000s >> 2009 Storm Forum

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Reged: Fri
Posts: 245
Loc: Beautiful Honolulu Hawaii
Tropical Depression 8 Forms! Tropical Storm GRACE in the Making ??
      #86964 - Fri Sep 25 2009 01:27 PM

Yep. It seems as though Invest 99L is now organizing rather quickly.

The wave that was to become Invest 99L has just been tagged in the past few hours. (Thanks to Black Pearl) And at this rate, I expect *at least* a TCFA (tropical cyclone formation alert) to be issued by the end of the day, if not a bona fide Tropical Depression.

Additionally, the NHC has just 'upped' the chances for cyclogenesis to level 'Orange', or 30% to 50% chance in the next 48 hours, but personally I think it's at *least* 50/50 within 2 days, just judging on the rapidly improving satellite signature.

The following visible animated satellite loop shows this 'invest' organizing quite rapidly, with pronounced low-level cyclonic turning and several obvious 'spiral rainbands', or banding features, starting to wrap tightly around the vorticity center.

(As an aside, notice too, in the last few frames, a nice example of 'convective turret penetration', when the upper turrets of the strongest thunderstorms penetrate some distance into the stratosphere. And the low angle of the setting sun highlights them quite nicely with bright reflectivities on the sunny (western) side of the disturbance and deep shadows on the eastern side, making for excellent contrast and thus showing the penetrative turrets quite clearly.)

NOTE: In the 1/2 hour since I wrote the above paragraph, NHC has again bumped up the chances for significant development to 'Red', or at least 50% in the next 48 hours, but the TWO (tropical weather outlook) accompanying the upgrade hints at possible Depression Status *within 24 hours*, when upper level winds are expected to *temporarily* become less favorable for continued stregthening.

The long-term (currently) looks for strengthening to resume as upper level winds again become more favorable, certainly to at least tropical storm strength (if it doesn't happen within the next 24 hours), and from there who knows how strong 'Grace' might become or where she'll go and ultimately end up.

Although most models (currently) forecast the developing cyclone to first move north and then turn sharply south onto it's own track, both are unanamious in bringing it to at least storm intensity by the end of the 5-day model run.

Correct me if I'm wrong, but this looks to be about the most organized thing that the Atlantic basin has seen since Fred languished, seemingly weeks ago.

About time we had a named storm! The PEAK of Hurricane Season came and went with NARY a Storm! Go figure?

Edited by CoconutCandy (Fri Sep 25 2009 06:00 PM)

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Reged: Fri
Posts: 245
Loc: Beautiful Honolulu Hawaii
Tropical Depression 8 Forms in Far Eastern Atlantic [Re: CoconutCandy]
      #86966 - Fri Sep 25 2009 04:40 PM

Well, there ya go! According to the NRL website, Invest 99L has organized sufficiently to lower the central pressure enough to increase the sustained winds to at least 30 Kts. and Viola! Tropical Depression 8 has made its' presence known.

I expect official advisories and forecasts from the NHC to be issued in 1/2 hour, or 5pm EDT. At this rate, it seems entirely reasonable to speculate that TD8 will become TS 'Grace' within the next 12 to 24 hours, before the upper level shear ticks up a notch or two. NHC dissipates the system in a few days due to strong shear, but who knows? If a decent low and/or mid level circulation persists, it could very well find itself in a more conducive environment by days 4 or 5, in which case regeneration is certainly not out of the realm of possibilities.

Certainly the most interesting thing (Western Pacific not included ... more on that later) that we've seen in quite some time!

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Posts: 65
Re: Tropical Depression 8 Forms in Far Eastern Atlantic *Killed -- Sent to Graveyard* [Re: CoconutCandy]
      #86970 - Fri Sep 25 2009 10:07 PM

This post was sent to the Hurricane Graveyard

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Reged: Fri
Posts: 245
Loc: Beautiful Honolulu Hawaii
Chances for What? [Re: rgd]
      #86972 - Fri Sep 25 2009 11:48 PM

'Chances' aside, it *IS* a legitimate tropical cyclone that organized rather quickly from a weak tropical wave with sparse convection, and perhaps is on it's way to becoming a named storm that will go into the 2009 record books for all posterity.

Further, I realize the shear will weaken it into an open wave in a day or two. But as I mentioned above, if a decent low/mid-level circulation persists, it could well find itself in somewhat more 'friendly waters' by days 4 to 5. And the track for advisory #2 is nudged slightly to the left of the first one, so we will just have to see. The fat lady hasn't nearly begun to sing quite yet!

Y'all enjoy the calm and peace while you can. The 'canes will be back next year when El Nino subsides. But don't let your guard down just yet. As they say, it only takes one to spoil you day.

Edited by CoconutCandy (Sat Sep 26 2009 07:27 AM)

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Reged: Fri
Posts: 245
Loc: Beautiful Honolulu Hawaii
Tropical Depression 8 Recent Observations [Re: CoconutCandy]
      #86973 - Sat Sep 26 2009 12:11 AM

A few more notes and observations, as new model data has just come in.

As mentioned above, the track has been adjusted slightly to the left of the original track.

More significantly, the model guidance *no longer* has this system sharply recurving, but instead is tightly clustered on a solid NW heading, before the shear sets in and weakens it to an open wave (and *perhaps* dissipation).

Even more interestingly, the intensity guidance (at least the SHIPS and IVCN) has the storm re-strengthening to a respectible 55 Kts. by 120 hours (day 5). And this is a good 15 to 20 Kts. *higher* than the intensity guidance for the previous advisory.

So, all and all considering, I'd hazard to speculate that even if TD8/Grace does weaken (perhaps to a wave) all is not said and done with this system.

Like x-Fred, it could conceivably make it all the way across 'the pond' and (unlike x-Fred) may regenerate when upper winds become more favorable.

So let's not count out or summarily dismiss TD8 'til we see just what transpires over the next 4 to 5 days. This could turn out to be rather interesting, from a purely meteorological perspective!


Edited by Ed Dunham (Sat Sep 26 2009 08:19 AM)

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