93L a headache - could be a big deal; Katia struggling but could threaten Bermuda

By: Levi32 , 3:27 PM GMT on September 01, 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 video went kind of long today, but there is a lot to talk about. Invest 93L is going to be a headache for forecasters this weekend and early next week, as it will likely meander around the northwest Gulf of Mexico for a few days before moving inland. A move straight NW into the heart of Texas is unlikely due to the ridge there, and a deflection either WSW or northeast along the periphery of the ridge is likely. The big question is which direction will it choose and when will it choose it. A shortwave trough moving into the eastern U.S. in 3-4 days will try to tug 93L northeast, but it may or may not succeed. I ramble about a lot of stuff in the video regarding the pattern, but the main point is that much is going to depend on how strong 93L is and how it influences its own environment. 93L's strongest outflow channel is going to be to the southeast towards the NW Caribbean during its life, and if it strengthens substantially into a strong storm, that outflow will help strengthen the ridge to the southeast of 93L, between itself and Hurricane Katia to the east. This ridge would then increase the southwesterly steering flow over the Gulf of Mexico, and thus 93L would help propel itself northeastward into Louisiana. Because I think 93L has a chance to get fairly strong while sitting over very hot water for 4-5 days, I think the eventual end-game will be a northeast move into the Louisiana/MS area, after an initial loop to the WSW off the Texas coast and then back northward. This forecast has a larger than normal amount of uncertainty due to the complex pattern involved with weak steering currents, and the computer models are solidly divided in half between an eventual northeast movement and a WSW movement into south Texas or northern Mexico.

The benefit from 93L may be that with several days in the NW gulf it is sure to bring coastal Texas at least some showers periodically, which would be welcomed by many. However, if 93L doesn't move inland quickly this weekend, that kind of time over the 31C waters of the gulf could allow it to strengthen significantly, and a hurricane would be likely if 93L is still over water come Monday. This is the concerning part of this situation. The ECMWF shows a worst-case scenario by having 93L miss the first trough and sit still in the NW gulf for 8 days, strengthening into a major hurricane before moving into Louisiana in response to a 2nd trough. While the Euro is the outlier showing this solution, it illustrates the fragility of this pattern and just how hard it is going to be to make 93L go anywhere. Don't be surprised if my track forecast has to change during the coming days, and everyone along the gulf coast from northern Mexico to the western Florida panhandle should keep a very close eye on 93L.

Hurricane Katia is finally eating too much dry air this morning, and she may no longer be a hurricane for the moment, as her low-level center is nearly exposed. Eventually she should overcome this and strengthen again, but probably not beyond Cat 3 during her lifetime. The models still point at Bermuda, and although I still think the track will shift west between Bermuda and Cape Hatteras, folks on that island should keep a close eye on Katia. An eventual move up towards the Canadian Maritimes as a weakening tropical storm could occur as well. Chances of affecting the U.S. are slim right now, especially if we have Lee in the Gulf of Mexico after this weekend, as the ridge that he should build between himself and Katia would help force her northward as well.

We shall see what happens!

Invest 93L Model Track Forecasts:



Official NHC Forecast for Tropical Storm Katia:



Tropical Storm Katia Model Track Forecasts:



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 Potential (green areas represent upward motion associated with the MJO):






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33. Levi32
1:11 AM GMT on September 02, 2011
Quoting spathy:
Hi Levi
Watch all your updates.
I love them.



BTW

Take care of your cold/allergies.

I heard that stuffiness.


Haha - Yes ma'am :P
Member Since: November 24, 2005 Posts: 635 Comments: 26754
31. Levi32
11:54 PM GMT on September 01, 2011
NHC track follows the model consensus into western Louisiana in 48 hours. This short of a time over water means a moderate tropical storm is all TD 13 would get to, making it a big water storm, dumping over a foot of rain in LA. Any slowing of this track or meandering in the NW gulf could result in a stronger storm. As I said this morning, if it's over water on Monday, it should be a hurricane. If it goes ashore before that, it's just a tropical storm.

Member Since: November 24, 2005 Posts: 635 Comments: 26754
30. WaterWitch11
11:52 PM GMT on September 01, 2011
ok....i'm sorry its working now.
Member Since: August 11, 2008 Posts: 3 Comments: 1924
29. Levi32
11:41 PM GMT on September 01, 2011
Quoting WaterWitch11:
i swear i just posted here. i love your blog, a lot of info. the video posted stops at 3:50. i do not think its on my end. thanks.


I've had nobody else have this problem, and it plays fine for me. Chances are it's on your end somewhere.
Member Since: November 24, 2005 Posts: 635 Comments: 26754
28. WaterWitch11
11:35 PM GMT on September 01, 2011
i swear i just posted here. i love your blog, a lot of info. the video posted stops at 3:50. i do not think its on my end. thanks.
Member Since: August 11, 2008 Posts: 3 Comments: 1924
27. Levi32
10:56 PM GMT on September 01, 2011
We have Tropical Depression #13

THIRTEEN, AL, L, , , , , 13, 2011, TD,
Member Since: November 24, 2005 Posts: 635 Comments: 26754
26. Levi32
7:46 PM GMT on September 01, 2011
Quoting swlaaggie:
Levi,

The fsu and psu sites still don't have the 12z euro up. Where do you obtain the euro runs shown on your blog?

Thanks.


Raleighwx
Member Since: November 24, 2005 Posts: 635 Comments: 26754
25. swlaaggie
7:33 PM GMT on September 01, 2011
Levi,

The fsu and psu sites still don't have the 12z euro up. Where do you obtain the euro runs shown on your blog?

Thanks.
Member Since: April 26, 2006 Posts: 0 Comments: 1032
24. AtHomeInTX
7:12 PM GMT on September 01, 2011

Quoting Levi32:


Well hopefully coastal Texas still gets some rain on the NW side if it's not too limited in that quadrant. Rain will be a huge issue for Louisiana though if this hangs around to give them perpetual water for 5 days straight. HPC had 18 inches over southern LA for the next 5 days.

Ouch! I had read "a foot" of rain in the New Orleans area.  SW LA is in as bad a drought as we are. I hope they get in on some of that.  Their fires don't respect borders.  Lol. I'm just kidding. Hope they get some for their own sake. And of course we'll take what we can get too.
Member Since: August 24, 2010 Posts: 0 Comments: 432
23. AllyBama
7:06 PM GMT on September 01, 2011
GO WEST!..LOL
Member Since: August 3, 2006 Posts: 133 Comments: 20647
22. Levi32
7:01 PM GMT on September 01, 2011
Quoting AtHomeInTX:
Thanks Levi. That EURO run is much less scary for everyone involved. Last night it had us under some crazy winds for 8 days. Now just I think four.  These models look farther away from us. So rain chances are probably nothing again. Sigh.  But if it wasn't going to be a rain maker anyway good riddance!  The dry wind on the back side will just add too our fire danger. Thanks again. :)


Well hopefully coastal Texas still gets some rain on the NW side if it's not too limited in that quadrant. Rain will be a huge issue for Louisiana though if this hangs around to give them perpetual water for 5 days straight. HPC had 18 inches over southern LA for the next 5 days.
Member Since: November 24, 2005 Posts: 635 Comments: 26754
21. Levi32
7:00 PM GMT on September 01, 2011
Recon found a broad center with westerlies, but the area of lowest pressures (~1010mb) is very large. We saw this with Irene. It will take a while to consolidate that into a tight low worthy of classification.

Member Since: November 24, 2005 Posts: 635 Comments: 26754
20. AtHomeInTX
6:56 PM GMT on September 01, 2011
Thanks Levi. That EURO run is much less scary for everyone involved. Last night it had us under some crazy winds for 8 days. Now just I think four.  These models look farther away from us. So rain chances are probably nothing again. Sigh.  But if it wasn't going to be a rain maker anyway good riddance!  The dry wind on the back side will just add too our fire danger. Thanks again. :)
Member Since: August 24, 2010 Posts: 0 Comments: 432
19. Levi32
6:28 PM GMT on September 01, 2011
The 12z ECMWF actually supports my track of 93L initially moving WSW closer to Texas and then looping back around northeast towards Louisiana, with a landfall on Tuesday next week. This setup would likely have 93L as a Cat 1 hurricane, which is much more realistic than what the 0z run showed last night - a 930mb hurricane after 8 days over water.

Member Since: November 24, 2005 Posts: 635 Comments: 26754
18. Hoff511
5:30 PM GMT on September 01, 2011
Thanks Levi!
Member Since: September 2, 2009 Posts: 0 Comments: 265
17. KeysieLife
5:20 PM GMT on September 01, 2011

Just got a chance to watch the video today. Thank you Levi, absoultely fantastic explanation on the trough/ridge setup and how it could effect these storms. Keep up the excelent work, you make Mets wish they had skills like that! =)
Member Since: September 10, 2010 Posts: 4 Comments: 409
16. Levi32
5:11 PM GMT on September 01, 2011
Quoting Boudreaux77:
If this thing in the Gulf actually hangs around for a while, wouldn't it upwell the cooler waters and actually keep itself from getting too big?


See the last couple posts above. If some worst-case scenario like the ECMWF came true and 93L becomes a major, then that would be a huge issue, but for a weaker system it will depend.
Member Since: November 24, 2005 Posts: 635 Comments: 26754
15. Boudreaux77
5:10 PM GMT on September 01, 2011
Nevermind, I see the answer to my question above. Thanks again for the updates.
Member Since: June 24, 2010 Posts: 0 Comments: 9
14. Boudreaux77
5:01 PM GMT on September 01, 2011
If this thing in the Gulf actually hangs around for a while, wouldn't it upwell the cooler waters and actually keep itself from getting too big?
Member Since: June 24, 2010 Posts: 0 Comments: 9
13. swlaaggie
4:59 PM GMT on September 01, 2011
Thanks for the rapid reply Levi.

Have a wonderful Labor Day weekend.
Member Since: April 26, 2006 Posts: 0 Comments: 1032
12. Levi32
4:53 PM GMT on September 01, 2011
Quoting swlaaggie:
Levi,

Thanks very much. As always, a great overview and quite educational.

As a 10 year resident of SW Louisiana, I've seen numerous storms(some quite large and some weaker) that tend to weaken just prior to landfall.

One in particular, Lilly(early 2000's) really weakened as she came closer to land. The theory in regard to Lilly was that she followed the path of a storm just 2-3 weeks prior and the prior storm sucked the heat content out of the water.

The coast off Louisiana is very shallow out to 40 miles, thus it has a lower heat content than deeper portions of the GOM.

If Lee sits out off the Louisiana coast for several days, I wonder if the models(especially the euro) are not taking the "churn up" of the water into account(deep or shallow). I'm not remotely suggesting this would kill the storm completely, but I do wonder if it might prevent the formation of a major type of hurricane?

Thoughts/corrections?

Thanks in advance and great job on your blog.


You make a valid point that I neglected to bring up in today's update, but it may become very relevant later. I don't think cold upwelling will be too much of an issue if the storm is far enough off the coast, but if it sits around just off of LA as you describe, those shallow waters could be cooled after a few days of a stronger system sitting there. 93L would likely have to be a stronger TS or weak hurricane to deplete the energy in the water though, even in the shallow shelf area.
Member Since: November 24, 2005 Posts: 635 Comments: 26754
11. Levi32
4:51 PM GMT on September 01, 2011
You may have noticed that I completely ignored 94L north of Bermuda this morning. This is another tiny system that will live for 12 hours if it acquires a warm-core structure. It actually already has one. I won't be happy if we throw away another 12-hour name, but it may deserve an upgrade later. I don't care about it because it is a zero threat. 93L and Katia, on the other hand, could cause impacts on land, and deserve attention.
Member Since: November 24, 2005 Posts: 635 Comments: 26754
10. swlaaggie
4:48 PM GMT on September 01, 2011
Levi,

Thanks very much. As always, a great overview and quite educational.

As a 10 year resident of SW Louisiana, I've seen numerous storms(some quite large and some weaker) that tend to weaken just prior to landfall.

One in particular, Lilly(early 2000's) really weakened as she came closer to land. The theory in regard to Lilly was that she followed the path of a storm just 2-3 weeks prior and the prior storm sucked the heat content out of the water.

The coast off Louisiana is very shallow out to 40 miles, thus it has a lower heat content than deeper portions of the GOM.

If Lee sits out off the Louisiana coast for several days, I wonder if the models(especially the euro) are not taking the "churn up" of the water into account(deep or shallow). I'm not remotely suggesting this would kill the storm completely, but I do wonder if it might prevent the formation of a major type of hurricane?

Thoughts/corrections?

Thanks in advance and great job on your blog.

p.s. When I told my wife about the potential for a storm, she immediately went to the computer and pulled up your blog. Trust me, that's the highest form of compliment. :-)
Member Since: April 26, 2006 Posts: 0 Comments: 1032
9. JGreco
4:46 PM GMT on September 01, 2011
Quoting Levi32:


Well if it gets tugged northeast it could certainly move near the Mississippi River Delta and then on into the MS/AL area. I think asking for a landfall actually in Florida like the GFS had yesterday morning is too much to ask from the trough, and I think a landfall will be farther west, but the panhandle could still get affected by the east side of a potential storm.


Just wondering because are weather tends to be more inclined towards what happens in Alabama and Mississippi. Ivan's landfall in Alabama devastated the area from Pensacola to Destin and brought sustained winds above Cat 3 to my area. That is why I am concerned about this landing as far East as let say Alabama or Mississippi, that is still on the East side for us:o
Member Since: September 22, 2005 Posts: 0 Comments: 322
8. Levi32
4:42 PM GMT on September 01, 2011
Quoting JGreco:
Hey Levi. Just wondering how far East is possible for the eventual landfall of the storm.Since I'm in the extreme Western Florida Panhandle, we sit exactly NE of the of the jutting tip of Louisiana which is the Southern most point in the North Gulf Coast region.. So its kind of frightening because there has been storms in the past that barely have missed the tip of Louisiana which launched them into Alabama putting us much closer to the East side. Just wondering how far towards Eastern Louisiana can this storm go?


Well if it gets tugged northeast it could certainly move near the Mississippi River Delta and then on into the MS/AL area. I think asking for a landfall actually in Florida like the GFS had yesterday morning is too much to ask from the trough, and I think a landfall will be farther west, but the panhandle could still get affected by the east side of a potential storm.
Member Since: November 24, 2005 Posts: 635 Comments: 26754
7. JGreco
4:39 PM GMT on September 01, 2011
Hey Levi. Just wondering how far East is possible for the eventual landfall of the storm.Since I'm in the extreme Western Florida Panhandle, we sit exactly NE of the of the jutting tip of Louisiana which is the Southern most point in the North Gulf Coast region.. So its kind of frightening because there has been storms in the past that barely have missed the tip of Louisiana which launched them into Alabama putting us much closer to the East side. Just wondering how far towards Eastern Louisiana can this storm go?
Member Since: September 22, 2005 Posts: 0 Comments: 322
6. Levi32
4:31 PM GMT on September 01, 2011
I fully expect a downgrade of Hurricane Katia next advisory. Her low-level center is now exposed.

If 93L is to become a hurricane it will have to remain over water after the weekend. A move inland sooner than that means it won't be a huge deal. We'll have to see. Folks should keep a close eye on this one.
Member Since: November 24, 2005 Posts: 635 Comments: 26754
5. seasntrees
4:02 PM GMT on September 01, 2011
I enjoy your "Tidbits" and have learned an abundance of information from you since signing up to the blog. Many thanks :)
Member Since: August 4, 2011 Posts: 0 Comments: 9
4. InTheCone
3:55 PM GMT on September 01, 2011
Thanks Levi, hope we don't get a meandering 'cane in the gulf!
Member Since: September 1, 2007 Posts: 0 Comments: 1990
3. Barefootontherocks
3:54 PM GMT on September 01, 2011
The XTRAP goes right over my house! LOL

Thanks for sharing your good thoughts on tropical weather.

Best wishes for a great second year at UAF.
Member Since: April 29, 2006 Posts: 162 Comments: 20423
2. daddyjames
3:51 PM GMT on September 01, 2011
Levi, thanks a million! Learned a lot today. Thanks for taking your time to explain all the possibilities. You are truly appreciated and respected by most (there are those trolls -lol) members of the blog.
Member Since: June 25, 2011 Posts: 2 Comments: 3735
1. Beachfoxx
3:45 PM GMT on September 01, 2011
Thanks Levi--- I'm no MET, but I have been watching these type storms for years.  We've got water temps of 89°.  Don't won't 93L dancing around in the GOM for to long...
Member Since: July 10, 2005 Posts: 157 Comments: 29391

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