Disturbance fizzeled in Eastern Atlantic

[Gustywind]

[Gustywind]

Eastern Pacific systems, monitoring Atlantic
Chris Dolce, Lead Meteorologist, The Weather Channel
Aug. 4, 2009 9:24 am ET


The Atlantic Basin remains quiet overall. However there is one area of interest well out in the eastern Atlantic.

An area of low pressure is located well southwest of the Cape Verde Islands between 30 and 40 west longitude. There continues to be some persistent convection and it will be monitored for slow development while moving off to the west.So far we've had one tropical depression in May this season and no named storms.
http://www.weather.com/newscenter/tropical/

[Ed Mahmoud]

Here's a bit closer look at the disturbance, along with a plot of some obs in the area. It actually looks less impressive on visible imagery than with IR. The thunderstorm area is elongating NW-SE today. There are some sparse surface obs in the region. Can't really identify much of a circulation aloft, and nothing at the surface. A high-res satellite loop (I have Meteosat imagery every 15 min) reveals two small vortices to the northeast of the disturbance. I circled them on the image below. Both lack convection and aren't likely to develop.

All models - GFS, Canadian, ECMWF take this disturbance W-WNW for the next 2-3 days then NW and out to sea well east of the Caribbean, as Derek noted. However, the models may be overdeveloping the disturbance. If it remains as it is, it'll probably just continue westward (and not develop, most likely). Of note are the weak trade winds indicated by the obs on the image. This indicates that the high to its north is weaker now, another sign that it'll start gaining latitude should it get better organized.

But there is a slight chance of development. Not high enough to warrant an invest yet. Probably won't develop until this Saturday. Hmm, that happens to be August 8th!

Cloud tops have warmed a touch, and although WxMan57 dismissed the 6Z GFS run on December 5, 2008 that showed the December 10th snow miracle, he seems right most of the time. Which is good, since he is a paid professional.


If he seems to think (unsaid, but reading between the lines) a Code Yellow as issued by the NHC is correct, it is probably correct.

[Ed Mahmoud]

Eastern Pacific systems, monitoring Atlantic
Chris Dolce, Lead Meteorologist, The Weather Channel
Aug. 4, 2009 9:24 am ET


The Atlantic Basin remains quiet overall. However there is one area of interest well out in the eastern Atlantic.

An area of low pressure is located well southwest of the Cape Verde Islands between 30 and 40 west longitude. There continues to be some persistent convection and it will be monitored for slow development while moving off to the west.So far we've had one tropical depression in May this season and no named storms.
http://www.weather.com/newscenter/tropical/

Do the on duty off camera mets at TWC ever deviate from the NHC script on development?

Not deviating when a system is approaching land is a good thing, minimizes confusion, increases the chances that people do what they are supposed to do, heed warnings, etc., but for a system 5 or 6 days minimum from land, would TWC ever deviate from the NHC script?

[Gustywind]

SAL

[Dean4Storms]

Thanks Wxman57, that more up to date visible does paint a less impressive system.

[wxman57]

Thanks Wxman57, that more up to date visible does paint a less impressive system.

You're welcome. I'll post additional shots today. I'm pulling for it to develop on Saturday, my pick for the 1st storm date since May. I don't think my chances are very good of hitting, as I'm totally dependent on this disturbance developing. There's nothing else out there that could develop by Saturday.

[Frank2]

wxman57,

Thanks for the update - as that Emeril fella would say, your synopsis has "brough it down a notch" since an hour or two ago...

It did seem formidable on the IR, but as you mentioned the VIS does reveal a much-less impressive system...

Thanks

[Sanibel]

Someone mentioned the wave following over Africa might be the better of the two. The last time two disturbances came off of Africa the second one was the contender. The second one has dried up slightly but this present wave shows the Atlantic is starting to burst waves so if the trend holds the second wave should also convect with red IR.

The season has warmed up a little. It will either support these waves or not. But the trend here is more to follow that will plant and form. Perhaps the MJO isn't here yet and the next pulse of waves will coincide with the MJO and have much different results?

[Sanibel]

Half-gelled isn't enough in negative conditions:

[wxman57]

Someone mentioned the wave following over Africa might be the better of the two. The last time two disturbances came off of Africa the second one was the contender. The second one has dried up slightly but this present wave shows the Atlantic is starting to burst waves so if the trend holds the second wave should also convect with red IR.

The season has warmed up a little. It will either support these waves or not. But the trend here is more to follow that will plant and form. Perhaps the MJO isn't here yet and the next pulse of waves will coincide with the MJO and have much different results?

You're correct in noticing that the trailing waves are more likely to develop. We saw that over and over again in 2008 on the archived MIMIC TPW data which can be accessed below the animation on this page:

http://cimss.ssec.wisc.edu/tropic/real- ... /main.html

And if you look at the models closely (GFS/ECMWF/Canadian), you'll see that they're actually developing the system closer to the coast of Africa, not the area that the NHC highlighted. Of course, that system lacks any significant convection so it'll have a tough time developing unless something changes.

As for any MJO pulse, the MJO has remained very weak this season. There are no indications of a pulse heading our way. Here's an excellent MJO page. I encourage everyone here to read the weekly MJO update (PPT or PDF files in the middle of the page).

http://cimss.ssec.wisc.edu/tropic/real- ... /main.html

Weekly update PPT:
http://www.cpc.ncep.noaa.gov/products/p ... update.ppt

Weekly update PDF:
http://www.cpc.ncep.noaa.gov/products/p ... update.pdf

[Aric Dunn]

I totally Agree with wxman57. This is by far the best wave this season and development is is at least probable. There is a piece of energy to the systems east that will catch up today and most likely help fire some deep convection later. development still few days out since its well attached to the ITCZ, but its already showing the tell tale signs
this one is a green light from me sometime late friday to sunday for development. At least when it becomes a becomes a official depression although i imagine will be looking at a pretty impressive circulation and envelope associated with it as it is a decent size system

[cycloneye]

Discussion by Dr Jeff Masters.

Posted by: JeffMasters, 3:18 PM GMT on August 04, 2009

A tropical disturbance embedded in the Intertropical Convergence Zone (ITCZ), near 9N 35W, is moving west at about 15 mph. The heavy thunderstorm activity associated with this tropical wave has changed little over the past 24 hours, and remains disorganized. This morning's QuikSCAT pass showed a moderate wind shift, but nothing resembling an organized surface circulation. Top winds were in the 20 - 30 mph range. Strong easterly winds are creating about 20 knots of wind shear over the wave, which is marginally conducive for development. The disturbance is about 300 miles south of the Saharan Air Layer (SAL), so dust and dry air should not hinder development over the next few days.

Given the disturbance's current lack of organization, combined with the presence of 20 knots of wind shear, any development should be slow to occur. The forecast wind shear along the storm's path over the next five days is predicted to remain at or below 20 knots, which should allow some slow development. Sea surface temperatures (SSTs) will warm from about 28°C to 29°C as the storm progresses westward. The GFS model has been indicating some development is possible in several of its runs over the past few days, but has not been consistent with this prediction. None of the other models show any development of the system. NHC is giving the disturbance a low (less than 30% chance) of developing into a tropical depression over the next two days, which is a good forecast. The GFS and ECMWF models predict the system will be approaching the northern Lesser Antilles Islands by Sunday. Both models forecast the development of a band of very high wind shear just to the north of the islands at that time, so the long-range survival of anything that might manage to develop is in doubt.

[wxman57]

It's looking less impressive on visible imagery now. No new surface obs since 12Z in the area. I don't think this warrants an invest at this time.

[Sanibel]

That said, you can never tell and we've seen busted waves like this burst and develop further west.


(Including Katrina and Andrew)

[wxman57]

That said, you can never tell and we've seen busted waves like this burst and develop further west.

(Including Katrina and Andrew)

Katrina had little or no convection when it was near 30W-35W. I'm looking at some saved satellite shots now of Katrina between August 4th-12th. Of course, it was moving toward an environment that was much more favorable for development than this disturbance is.

[HURAKAN]

We need to use HAARP to give this wave some life!!!

[cycloneye]

Ramsdis has now a floater over it.



Floater Java loop

[Blown Away]

Nice little rotation near 9N/35W on the visible and that's where we were seeing the deep reds on the IR. At least we have something to look at and chat about.

[alan1961]

It already has good mid level rotation and upper air support. I doubt the NHC is taking into account any reduction in Coriolis effect or separation from the ITCZ but you never know.

My guess is they are just waiting to see if the dry air environment poofs the storm before sending the price of oil over $75 a barrel.

now now nimbus dont be cynical