Bret leaving; 99L may develop; CATL wave possibly a problem down the road

By: Levi32 , 3:12 PM GMT on July 20, 2011

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Please note that these tidbits do NOT reflect the official forecasts of the National Hurricane Center, and should not be taken as such. While tropical cyclones exist in the Atlantic, the official NHC forecasts will be posted in the lower part of this blog. Please refer to those when making decisions, and heed the advisories and evacuation statements of your local National Weather Service Office.

If you can, playing the video in HD makes it much easier to see things. The video will play in low quality by default. If HD quality isn't available, then it will be in a few minutes. Let me know if you have problems with the video, and please feel free to ask me any questions regarding what I talk about in these tidbits, or about the weather in general. You can post in either of my blogs or on Youtube. I will do my best to answer. Thanks for stopping by!

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The Atlantic remains a fairly active place for mid-late July. Tropical Storm Bret continues to hold his own, despite being sheared and injected with dry air, and is slow to weaken as he moves northeast, though he will continue to weaken and eventually fizzle as he integrates into the mid-latitude westerlies. A passing shower or two may touch Bermuda, but he is no real threat to anyone.

A feature that I neglected to mention over the last few days is the old competing circulation that was initially just northeast of Bret along the frontal boundary that spawned them both, and this low is now quite far out to the northeast of Bret, looking very well-defined and tropical in nature, perhaps more so than Bret. This feature has been tagged invest 99L, and now has a high chance of development from the NHC. This is another random middle-of-nowhere situation where the system could have been classified a while ago, but won't be unless it persists for quite a long time, due to the fact that it is in the middle of nowhere. We may get TD 3 or Cindy out of this, but it will be a subjective decision by the NHC as to whether we do or not.

The bigger story that may develop next week is the large tropical wave in the central Atlantic. This wave, despite lacking convection, has a deceptively deep moisture field with it, and although there is dry air wrapping in from the northwest, this moisture field will have a chance to consolidate into a stronger area of low pressure once the wave gets farther west. The models are all hinting at this wave consolidating a bit more just north of the Caribbean in 5-7 days. A part of this wave may go into the Caribbean while the northern part continues north of the Caribbean, but either way, the energy will need to bundle before this wave can have a shot at development. As mentioned yesterday, a trough is forecasted to be over the western Atlantic around the time when this wave gets north of the Caribbean, which could recurve any system that tries to develop. However, as I also mentioned, this pattern is rather fragile, and the trough will not be in that position for very long before lifting out. In fact, some of the latest model runs, including the ECMWF and the CMC, show the system getting caught beneath the U.S. ridge as it builds northeastward, bringing the system westward towards the U.S. coast and the Bahamas.

With a fragile pattern like this, as always, timing will be everything. Whether we get development north of the Caribbean will also play a role in whether the wave recurves. I show in the video how one of the top analogs for the 500mb pattern coming up in 8-10 days is that of Hurricane Allen in 1980, which came across the northern Caribbean and Gulf of Mexico into southern Texas as a Cat 4. While this doesn't mean our wave will be anything like Allen, the big point is that this kind of a pattern can favor a storm coming underneath the big U.S. ridge when it makes one of its August moves northeastward. If this pattern does indeed set up this way, it is reminiscent of the pattern I have warned about that could develop at times this season and bring storms to the coast. There are a lot of ifs still to be resolved with this wave, and it may never develop, but it may also be a problem to watch next week, and thus will be monitored closely.

We shall see what happens!



Tropical Storm Bret Official NHC Track Forecast:



Invest 99L Visible/IR2 Floater (click image for loop):



Caribbean/East Pacific Visible/IR2 Satellite (click image for loop):



Central Atlantic Visible/IR2 Satellite (click image for loop):



Atlantic Tropical Surface Analysis:



200mb Vertical Velocity (green areas represent upward motion associated with the MJO):






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22. MeterologyStudent56
6:52 PM GMT on July 21, 2011
Quoting Levi32:
0z ECMWF operational shows no development with the central Atlantic wave, but its ensembles continue to show variance, and thus a storm, moving across the Bahamas in 6-7 days. Besides the NOGAPS, the other models remain sketchy on development.



Levi,

This might seem as a dumb question , but can you please explain the positon of the A/B high this year.
Ive been told that it puts the bahmamas and florida and the northern carribean islands at risk.
Member Since: July 21, 2011 Posts: 1 Comments: 332
21. CybrTeddy
6:04 PM GMT on July 21, 2011
Ensembles caught Bret while the Operational showed nothing, same with Arlene.
Member Since: July 8, 2005 Posts: 259 Comments: 24972
20. Levi32
2:24 PM GMT on July 21, 2011
0z ECMWF operational shows no development with the central Atlantic wave, but its ensembles continue to show variance, and thus a storm, moving across the Bahamas in 6-7 days. Besides the NOGAPS, the other models remain sketchy on development.

Member Since: November 24, 2005 Posts: 635 Comments: 26754
18. Levi32
10:35 PM GMT on July 20, 2011
We have Tropical Storm Cindy, which will remain weak as she moves over cooler waters. 2 storms on the map and it's only July.

Member Since: November 24, 2005 Posts: 635 Comments: 26754
17. Hoff511
8:47 PM GMT on July 20, 2011
Thanks Levi!
Member Since: September 2, 2009 Posts: 0 Comments: 265
16. TomTaylor
8:46 PM GMT on July 20, 2011
Quoting Levi32:


Link

Get with the program Tom. You're supposed to have all the links :P
oh silly me, I already have that link

Just never used model runs from that site so I didn't know what they looked like lol

edit: just played around a bit with that site...idk why I never used it before, some good stuff there, especially for the ECMWF. It seems 90% of the time all the websites I run into with ECMWF runs only have like 3 variables for that model (500mb geo height, 850mb vort, surface pressure).
Member Since: August 24, 2010 Posts: 19 Comments: 4358
15. Levi32
7:34 PM GMT on July 20, 2011
Quoting TomTaylor:
Nice update, as usual, levi


could you post the link to this image please?


Link

Get with the program Tom. You're supposed to have all the links :P
Member Since: November 24, 2005 Posts: 635 Comments: 26754
14. Levi32
7:33 PM GMT on July 20, 2011
BEGIN
NHC_ATCF
invest_RENUMBER_al992011_al032​011.ren

AL, 03, 2011072018, , BEST, 0, 345N, 547W, 30, 1009, TD

We have Tropical Depression #3.
Member Since: November 24, 2005 Posts: 635 Comments: 26754
13. TomTaylor
7:32 PM GMT on July 20, 2011
Nice update, as usual, levi

Quoting Levi32:
12z ECMWF shows little - just an open wave over Cuba and the western Bahamas. This illustrates that the models aren't solidly coming onboard with development, and the ones that do are still weak, so development of this wave is far from guaranteed. However, given the prospects of potential land interaction, the feature should be watched closely in case it does develop.


could you post the link to this image please?
Member Since: August 24, 2010 Posts: 19 Comments: 4358
12. AtHomeInTX
7:01 PM GMT on July 20, 2011
Thanks Levi. Fascinating as usual. Haven't thought about Allen in a while. I guess when the long trackers do actually make it to Texas they make it count. Sigh. ;)
Member Since: August 24, 2010 Posts: 0 Comments: 434
11. Levi32
6:53 PM GMT on July 20, 2011
12z ECMWF shows little - just an open wave over Cuba and the western Bahamas. This illustrates that the models aren't solidly coming onboard with development, and the ones that do are still weak, so development of this wave is far from guaranteed. However, given the prospects of potential land interaction, the feature should be watched closely in case it does develop.

Member Since: November 24, 2005 Posts: 635 Comments: 26754
9. WxCFL
5:18 PM GMT on July 20, 2011
Thanks, Levi!
Member Since: August 27, 2010 Posts: 0 Comments: 13
8. lavinia
5:12 PM GMT on July 20, 2011
Thanks Levi. Great update! :)
Member Since: September 2, 2008 Posts: 0 Comments: 217
7. earthlydragonfly
4:23 PM GMT on July 20, 2011
Great update as alway!!
Member Since: July 1, 2005 Posts: 10 Comments: 1683
6. hydrus
3:58 PM GMT on July 20, 2011
Thank you, good update..I remember Allen well..It was a monstah..90 mph gusts on the Tortugas..
Member Since: September 27, 2007 Posts: 1 Comments: 24766
5. Levi32
3:53 PM GMT on July 20, 2011
Quoting jonelu:
Just bought an 1928 Spanish style in West Palm Beach...It has some of the old style shutters...but some windows are bare. I guess I should start looking into some panels with this years set up...


That is absolutely always a great idea Jonelu, no matter what kind of a season is expected. The common saying that "it only takes one" is very true, and it could happen to you in any year.
Member Since: November 24, 2005 Posts: 635 Comments: 26754
4. jonelu
3:51 PM GMT on July 20, 2011
Just bought an 1928 Spanish style in West Palm Beach...It has some of the old style shutters...but some windows are bare. I guess I should start looking into some panels with this years set up...
Member Since: October 31, 2007 Posts: 2 Comments: 884
3. NavarreMark
3:46 PM GMT on July 20, 2011
Thanks for the update Levi.
Member Since: September 2, 2010 Posts: 0 Comments: 3989
2. TropicalAnalystwx13
3:43 PM GMT on July 20, 2011
Thanks Levi!
Member Since: July 6, 2010 Posts: 113 Comments: 34205
1. rmbjoe1954
3:17 PM GMT on July 20, 2011
Thanks, Levi. This is very informative.
Member Since: June 16, 2005 Posts: 0 Comments: 1618

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Masters student in tropical meteorology at FSU. Raised in Alaskan blizzards, but drawn toward tropical cyclones by their superior PGF.

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