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Archives 2000s >> 2007 News Talkbacks

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Thunderbird12
Meteorologist


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Re: Tropical Depression Developing East of Caribbean [Re: Storm Hunter]
      #77623 - Fri Aug 31 2007 02:41 PM

Recon data seems to indicate a relatively weak and broad surface circulation in 94L. Max flight-level winds so far (that I have seen) are 28 kts. It'll probably be classified at the next advisory time, even if the plane doesn't find anything tight enough to merit a vortex message. The satellite signature of the storm is impressive, but the available data so far indicates that the surface reflection is still getting its act together.

I also noticed that some convection has flared up around 15N/35W, in the vicinity of the tropical wave/broad low pressure that was getting a brief mention in the TWO for the last couple of days before being dropped. If that persists, it may start getting mentioned again, but nothing is imminent.


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typhoon_tip
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Re: Tropical Depression Developing East of Caribbean [Re: MikeC]
      #77624 - Fri Aug 31 2007 02:50 PM

I will be quite surprised if this is not a depression in the 5pm and it may develop substantially overnight tonight.

The last 3 frames here: http://www.ssd.noaa.gov/goes/flt/t1/loop-vis.html Clearly show an accelerating cyclonic torque centered very close to 11.5N/58W -- of course this may vary from official.

Rapid improvement in sat presentation has commenced.

Deep layer wind analysis shows very little shear. As the convection potency has increased the transfer of mass to the upper levels, that injection enhances the outlfow in an already fairly favorable 200mb to begin with.. This means that the system has an above average evacuation being established. (There is also a thermodynamic process involved in the latent heat release of convection but that may be over folk's heads).

Oceanic heat content is quite high where 94L is and will only increase along its extrapolated path. There was some question of turbulent overturning left in the wake of Dean, but given to the depthy thermoclines of the Caribbean, and observing SSTs, this does not seem to be a problem.

The dry air that was likely contributory in preventing more robust development heretofore is still prevalent. However, belated but not denied is the key here... The dry air can be overcome given time via storm-centric production of increasing theta-e (moisture in atmosphere). In other words, the developing TC is producing a bit of its own core from which to fester within.

The reason there is only a vague presentation in the models may have to do with the models trying to initialize for a pressure perturbation that is all of 2mb lower than standard sea-level; and also relative to the ambient observed pressures in that area. As the system develops further, however, eventually the models will sniff out its presents more clearly and we will likely see some different solutions emanating rather abruptly. Fwiw, the ECM's 12Z solution is a bit more robust now after having lost it for several runs, so perhaps we are beginning this process now.

John

Edited by typhoon_tip (Fri Aug 31 2007 02:53 PM)


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Rabbit
Weather Master


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Re: Tropical Depression Developing East of Caribbean [Re: typhoon_tip]
      #77625 - Fri Aug 31 2007 03:25 PM

very doubtful now that it will be upgraded at 5--NRL still has it as 94L and the winds have been lowered back to 30 mph

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HCW
Storm Tracker


Reged: Fri
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Re: Tropical Depression Developing East of Caribbean [Re: Rabbit]
      #77627 - Fri Aug 31 2007 04:25 PM

Quote:

very doubtful now that it will be upgraded at 5--NRL still has it as 94L and the winds have been lowered back to 30 mph




I am going to have to disagree with that since it's listed as noname06 now on the navy site Is there any chance that this could affect the US with this pattern that we are stuck in ?

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LoisCane
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Re: Tropical Depression Developing East of Caribbean [Re: HCW]
      #77628 - Fri Aug 31 2007 04:29 PM

It was upgraded on will be officially at 5. See the home page.

Next run of models will have the recon data and will be interesting to see what it can do.
Not moving all that fast.

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hurricaneguy
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Re: Tropical Depression Developing East of Caribbean [Re: HCW]
      #77629 - Fri Aug 31 2007 04:30 PM

Quote:

Is there any chance that this could affect the US with this pattern that we are stuck in ?




Not really. This storm has a Dean path written all over it. It will be just a little further south. The ridge breaking down theory has just as good of chance as that ULL had of sending Dean to the GOM, and we all know how that turned out. This will be a Central America threat.

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StrmTrckrMiami
Weather Guru


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Re: Tropical Depression Developing East of Caribbean [Re: hurricaneguy]
      #77630 - Fri Aug 31 2007 07:49 PM

It seems that the majority of the depressions and storm systems are on the path twords Mexico this year. Looks like another Dean for Mexico and Jamaica (poor jamaica) What do you guys predict the hurricanes will do? Will they follow this track or some end up in Florida?

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Storm Hunter
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Re: Tropical Depression Developing East of Caribbean [Re: StrmTrckrMiami]
      #77631 - Fri Aug 31 2007 08:03 PM

right there at sunset on TD 6 a good development of storms flared up....looks to still be expanding in lastest IR sats and on the AVN loop. It should be right over where the center should be... Still a little curious about the ridge off the SE of US in 4-5 days... if it holds, this appears to be another system being pushed right along into central america.

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Wx Data: KFLPANAM23 / CW8771
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typhoon_tip
Meteorologist


Reged: Wed
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Re: Tropical Depression #6 Forms East of Caribbean [Re: MikeC]
      #77635 - Fri Aug 31 2007 09:16 PM

This may be interesting to some...

Barbados is located at 13N/59.3W

As of the 8:05, TD6 is located at 12N/59.3W.

So, the TD is currently passing due S of the Isle of Barbados at a distance of 60 nautical miles.

Now...why that is particularly interesting for me is because they are reporting 2 consecutive hours of sustained 30+mph winds from the E. For a system of mere TD ranking, 60N miles is heck of a lot of distance to be effecting that kind of wind speed.

There could be other explanations, of course, but could it be that we have TS already?

Stay tuned!

Edited by typhoon_tip (Fri Aug 31 2007 09:35 PM)


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Storm Hunter
Veteran Storm Chaser


Reged: Wed
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Re: Tropical Depression #6 Forms East of Caribbean [Re: typhoon_tip]
      #77636 - Fri Aug 31 2007 09:28 PM

been reading that too with Obs. from Barbados.. was wondering with the NICE CDO we have now with TD6, could it be a TS now? or was the winds a thing of TD and strong westerlies coming together, to give some good winds to the island?... Some of the 00Z runs are coming out... nice little shift showing up? One thing i have noticed, seems to me that this time the center of the high will be forming off the New England area, instead of more to the south where the last one was with Dean? Anyone else seeing this... I KNOW its way down the road, but looking at the globals... seems like this may be a little different setup then Dean? On time will tell, but with the shift showing up in a 00Z runs... (ones i have seen so far)... this might be something we need to watch closely.... **I know the models will jump around a lot until we they get a good handle on the system and the surrounding enviroment***

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Wx Data: KFLPANAM23 / CW8771
2012== 23/10/9/5 sys/strms/hurr/majh



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typhoon_tip
Meteorologist


Reged: Wed
Posts: 573
Re: Tropical Depression #6 Forms East of Caribbean [Re: Storm Hunter]
      #77637 - Fri Aug 31 2007 09:44 PM

Quote:

been reading that too with Obs. from Barbados.. was wondering with the NICE CDO we have now with TD6, could it be a TS now? or was the winds a thing of TD and strong westerlies coming together, to give some good winds to the island?... Some of the 00Z runs are coming out... nice little shift showing up? One thing i have noticed, seems to me that this time the center of the high will be forming off the New England area, instead of more to the south where the last one was with Dean? Anyone else seeing this... I KNOW its way down the road, but looking at the globals... seems like this may be a little different setup then Dean? On time will tell, but with the shift showing up in a 00Z runs... (ones i have seen so far)... this might be something we need to watch closely.... **I know the models will jump around a lot until we they get a good handle on the system and the surrounding enviroment***




Actually, I am not really inclined to think it is all that different than Dean's set-up at this time; though like snowflakes, no two patterns are "identical" either.

The -GLAAM (Global Atmospheric Angular Momentum) is very powerfully locked in an anomalous state at this time...

Moreover, the graphical presentation of where the crux of that anomaly distribution is situated is along and beneath 30N, and N of 30S... What that means is, -GLAAMs are correlated with longitudinal biases in the field and therefore, there is less likelihood that a wayward opening in the ridge will suddenly emerge and draw this system up; the meridional incursion (or in other words, increased troughing) into sufficiently south latitudes becomes anticorrelary and thus doubtful, given to this background overwhelming signal to maintain a stronger subtropical ridge axis.

That is far from absolute, of course! The GLAAM is a scalar value that is a calculation of integrated torque via several sources, throughout the atmosphere as a whole. It is not a prognostic tool, it is a measurement.

That being said, until this deeply negative anomalous state starts to show a positive modality, it is just the lesser of likelihoods at this time that meridional avenues will open up. It is the best way to use this observable teleconnector "responsibly", as possible correction scheme for forecast models. In this case, however, the models are pretty clearly persistent with the ridge and therefore, we have little room to doubt their veracity -- even at this extended lead; highly unusual but this is probably directly the cause in why the Global models did so terrifyingly beautiful predicting the path of Dean. They were locked into a persistence pattern where subtropical ridging was anomalously strong along 30 to 35N.

I was going over the 300mb, 500mb, and 700mb loops of the tropical Atlantic for the next week's worth of hours and across several runs of the GFS, there is indications of deep layer brick migrating W through the SW Atlantic Basin, across the Bahamas and west through the Gulf, in perfect tandem with "Felix's" probable forced S path.

John

Edited by typhoon_tip (Fri Aug 31 2007 09:52 PM)


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Ed DunhamAdministrator
Former Meteorologist & CFHC Forum Moderator (Ed Passed Away on May 14, 2017)


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Re: Tropical Depression #6 Forms East of Caribbean [Re: typhoon_tip]
      #77638 - Fri Aug 31 2007 10:04 PM

"but could it be that we have TS already?"

No, not at all. The normal wind at Barbados at this time of year is out of the east at about 15mph (think "Trade Winds"). At 9pm the wind at Barbados was out of the east at 32mph (at 8pm they reported a gust to 49mph). The island is currently experiencing the northern edge of the CDO. Because the normal wind flow is being enhanced by the TD to the tune of about 17mph does not mean that the winds near the center of the system are at TS strength - at least not yet. Same thing at St Lucia - normal wind is ENE at 16mph, but currently NE at 29mph. Grenada, where the normal tradewind flow is blocked by the TD circulation, has NNE winds at 7mph - and Grenada is just a little farther away from the TD center than Barbados is. (I guess thats why they call them the Windward Islands ). This is a case where data on the edge of the system has to be weighed with other known meteorological and climatological factors.
ED





Edited by typhoon_tip (Fri Aug 31 2007 10:11 PM)


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typhoon_tip
Meteorologist


Reged: Wed
Posts: 573
Re: Tropical Depression #6 Forms East of Caribbean [Re: Ed Dunham]
      #77639 - Fri Aug 31 2007 10:13 PM

Quote:

"but could it be that we have TS already?"

No, not at all. The normal wind at Barbados at this time of year is out of the east at about 15mph (think "Trade Winds"). At 9pm the wind at Barbados was out of the east at 32mph (at 8pm they reported a gust to 49mph). The island is currently experiencing the northern edge of the CDO. Because the normal wind flow is being enhanced by the TD to the tune of about 17mph does not mean that the winds near the center of the system are at TS strength - at least not yet. Same thing at St Lucia - normal wind is ENE at 16mph, but currently NE at 29mph. Grenada, where the normal tradewind flow is blocked by the TD circulation, has NNE winds at 7mph - and Grenada is just a little farther away from the TD center than Barbados is. (I guess thats why they call them the Windward Islands ). This is a case where data on the edge of the system has to be weighed with other known meteorological and climatological factors.
ED






I thought of this, Ed. However, I'm considering the 60nautical miles from the central axis of the circulation center, and that is a pretty far distance...even when considering the background factors, to be registering that kind of velocity.


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Storm Hunter
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Re: Tropical Depression #6 Forms East of Caribbean [Re: typhoon_tip]
      #77640 - Fri Aug 31 2007 10:42 PM

i may already know the answer to this question, but wanted to check with someone is knows for sure... Does the UCF damage impact model plot (Experimental).... run off the GFDL, or is it a serious out models together? I think i read some where online it was a few other things combined and weighed some on the GFDL... Anyone know for sure?

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typhoon_tip
Meteorologist


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Re: Tropical Depression #6 Forms East of Caribbean [Re: MikeC]
      #77641 - Fri Aug 31 2007 10:45 PM

Rather than speculating, let's do the Meteorology:

At 8:00pm, Barbados was reporting a sea-level pressure of 1010.7mbs

At 8:05pm, NHC reported a TD depth of 1008mbs, at about precisely 60 nautical miles due south of Barbados at that time.

Since NHC does not include decimal values in their depth assessments, I will go ahead and round the 1010.7mb to 1011mb for consistent units.

Ed wants to give 15mph-worth of the 32mph, back to background trade wind phenomenon, which actually is an assumption because even though trades consistently blow, they do not do so at the same velocity relative to pressure patterns. In reality, we don't know what the trade forcing into the system was as of 8pm, but for sake of discussion, we'll just assume it was 15mph-worth. That means that 17mph-worth of velocity is hypothetically storm generated.

Now, the pressure differential between Barbados and TD6 as of 8pm was ~ 4mbs. There is a general rule that works to a very close approximation: 1mb nearly = 1kt. 4mbs thus equates to 4kts.

So, immediately there is a discrepancy here. If 4mb = 4kts, 4kts certaindly does NOT atone for 17mph, considering that 1mile is 0.864 knots. That means the 4.62mph...or essentially 5mph, sticks us with an unexplained 12mph using this method. Something is adding into this to cause the +12mph

One possible explanation for this disparity is that the trade wind forcing at this time is actually stronger than usual, and thus, Ed has a very strong point: The correction may go the other way and we may yet still have a depression. In other words, even though climate argues for 15mph of trades, we may in fact have (15mph-trade) + (12mph-trade-anonamaly) to consider.

The other possible explanation is that they are wrong about the 1008mb of pressure. They do not directly specify in the 8:05 discussion whether that is based on the last RECON trip or not.

Either way, the available evidence does tend to support Ed's point of view on this.

The other thing to remember is to look at ALL the data, not just these pretty colored sat videos. Seeing as this is about to cross the axis of the Islands, we should know in a hurry if one of these islands happens through an inflow jet that is 40mph or not.

John

Edited by typhoon_tip (Fri Aug 31 2007 10:49 PM)


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Storm Hunter
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Re: Tropical Depression #6 Forms East of Caribbean [Re: typhoon_tip]
      #77642 - Fri Aug 31 2007 10:57 PM

hmm... just noticed this... with miss piggy and kermit (NOAA2 and NOAA3) being in the islands tomorrow... looks like from 01/2100Z to 02/1430Z there will be an aircraft flying the system (TD 6) [minus about 3 hrs].. along with AF recon... so looks like the HRD will be getting some good research data from this system, if all goes planned! Looks like as of tonight, the next recon will not be out there til, about 01/0930Z?

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Wx Data: KFLPANAM23 / CW8771
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Ed DunhamAdministrator
Former Meteorologist & CFHC Forum Moderator (Ed Passed Away on May 14, 2017)


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Re: Tropical Depression #6 Forms East of Caribbean [Re: typhoon_tip]
      #77643 - Fri Aug 31 2007 11:08 PM

You're right - the 15mph was sort of an educated guess. I used the winds at Barbados at this time last night and figured that the Atlantic ridge probably hadn't changed much in the past 24 hours. We'll all know soon enough since the TD center should pass over (or very close to) Grenada at about 0500AST and Grenada is a 24hour station, i.e., they take weather observations all night.

Grenada Weather Observations

Cheers,
ED


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typhoon_tip
Meteorologist


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Re: Tropical Depression #6 Forms East of Caribbean [Re: Ed Dunham]
      #77644 - Fri Aug 31 2007 11:18 PM

Quote:

You're right - the 15mph was sort of an educated guess. I used the winds at Barbados at this time last night and figured that the Atlantic ridge probably hadn't changed much in the past 24 hours. We'll all know soon enough since the TD center should pass over (or very close to) Grenada at about 0500AST and Grenada is a 24hour station, i.e., they take weather observations all night.

Grenada Weather Observations

Cheers,
ED




Excellent inclusion!

Our normal users have the advantage of some spectacular Met on-going...


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Beaumont, TX
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Re: Tropical Depression #6 Forms East of Caribbean [Re: Ed Dunham]
      #77645 - Fri Aug 31 2007 11:33 PM

Some of the models are showing a more northern track after four days. Is it possible the high won't build as far as it is supposed to or that
there will be a weakness somewhere? I suppose it is still too early to tell. It looks like it is headed straight for Belize but a lot can
happen in four days so I do not think the Gulf Coast should dismisss the storm just yet.


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HanKFranK
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down deep [Re: Ed Dunham]
      #77646 - Fri Aug 31 2007 11:36 PM

td 6/felix has a heaping collection of model support taking it wnw on a dean redux path. there don't seem to be any synoptic scale caveats here... looks like a straightforward forecast. dean churned the waters along future felix's path... look for a lesser version of the storm, but a similar path seems perfectly reasonable. the more strengthening the more northerly a path is likely. a weaker storm will likely scuttle in nicaragua, a stronger one might head for the yucatan. the emphasis NHC is placing on 'might be a major hurricane' is probably well-founded.
models starting to snoop on the african waves again. not much support for the elongated monsoon trough near 35w with the wave-enhanced convective blip. it will still have a decent chance if a follow-on wave doesn't overtake it... for slow development like the 6/felix system out in front of it.
following wave train is all developed by the 18Z GFS. one shows as a long-track hurricane there, with a dubious refusal to recurve into a weakness in the eastern atlantic. persistent disturbed weather near the southeast coast shows some suspicious activity but no tropical cyclone development, but that will be an area to watch nonetheless. the typhoon poised to hit japan after being blocked by a strong ridge, and the future track of henriette in the eastpac into the baja seem to suggest ridging near the east coast in the upcoming timeframe. have to be vigilant for one of these things to develop further north and also take a westerly track.
HF 0336z01september


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