Dr. Jeff Masters' WunderBlog

La Ni�a is gone

Posted by: Dr. Jeff Masters, 03:13 PM GMT del 11 Maggio 2006

The La Ni�a of 2006 proved to be short-lived. Sea Surface Temperatures (SSTs) in the eastern Pacific near the Equator have returned to near-normal values over the past month, according to the latest El Ni�o advisory issued today by the Climate Prediction Center (CPC). We are now in what is characterized as ENSO-neutral conditions (or El Ni�o-neutral conditions), which means that there is neither an El Ni�o nor a La Ni�a occurring. This is the case about 45% of the time, and was true for March through December of 2005. The CPC expects El Ni�o-neutral conditions to continue for at least the next 3-6 months, which means for all of hurricane season. The 2006 La Ni�a was an unusual one, because it started very late--no La Ni�a of similar magnitude has ever formed in the middle of winter, as this one did. However, the demise of this year's La Ni�a came at the usual time such events end--April and May are the typical months for the demise of both La Ni�a and El Ni�o.

How will this affect the hurricane season of 2006?
So, what does all this portend for the upcoming hurricane season? It is well-known that the presence of a La Ni�a usually means more Atlantic hurricanes, and stronger hurricanes, too. This is because the large-scale wind circulation that develops during a La Ni�a keeps wind shear levels relatively low over the main development region for hurricanes in the tropical Atlantic. So, the demise of La Ni�a is good news for those of you living in Hurricane Alley. However, before we get too cheerful about this, it is worth remembering that the unbelievable Hurricane Season of 2005 occurred in El Ni�o-neutral conditions, and El Ni�o-neutral conditions are expected for this hurricane season, too. So, let's look at some other factors that will influence this year's hurricane season.

Figure 1. Comparison of this year's May SST anomalies with last year's. Image credit: NOAA.

SST comparison--this year vs. last year
Let's compare last year's SST anomalies (the difference in temperature between observed and normal) with this year's, to see how things have changed (Figure 1). The key things to look at are the SSTs in the Caribbean and the tropical Atlantic between Africa and the Antilles Islands, since this is where 85% of all major hurricanes form. While SSTs are .5 to 1.5 degrees above normal--which is a lot!--SSTs are a full degree Centigrade cooler this year than last year at this time. This reduction in SSTs should keep this year's hurricane season from producing early major hurricanes, like Dennis and Emily of July 2005. However, once we enter the prime hurricane months of August through October, expect another above normal year for hurricanes and intense hurricanes. My worst-case scenario for 2006 is a year similar to 2004, which was awful, but modest compared to 2005. My best-case scenario is a year like 1995, which was still very active, but the Bermuda High set up much farther east and recurved most storms before they hit land. Of course, this would be bad for the northeastern Leeward Islands, which got pounded in 1995.

The Gulf of Mexico SSTs are much warmer this year than last, due in part to the record warm temperatures the U.S. experienced in January and April. This may allow for more intense that normal June systems to develop in the Gulf this year. However, remember that systems that develop in the Gulf usually only last a day or two, which doesn't give them much time to strengthen before they hit land. There has only ever been one major hurricane in June (Audrey of 1957).

The other item of interest is that the pattern of SSTs over the eastern Pacific is much different this year versus last year. Waters near the Equator were much warmer last year, thanks to the lingering effect of the El Ni�o event early in the year. There is also a much warmer pool of water north of Hawaii this year. These differences may end up having a significant influence on this year's jet stream pattern, and where the Bermuda high ultimately sets up camp. The jet stream and Bermuda high determine how hurricanes are steered, but unfortunately we don't know enough about long-range influences of unusual SST patterns on the weather to be able to predict where this year's hurricanes are likely to be steered. The bottom line is that SSTs are cooler and have a much different pattern this year compared to last year, and thus we should not expect a continuation of last year's ridiculously hyperactive, once-in-a-lifetime hurricane season.

Outlook for the rest of May
SSTs are already warm enough to support hurricane formation in the Gulf of Mexico, and the entire tropical Atlantic. What is saving us are the strong upper level winds of the jet stream, which has been dipping far to the south and creating lots of wind shear. The jet stream is forecast to remain active and fairly far south for at least the next two weeks, which should maintain unfavorable levels of wind shear over the Atlantic for the remainder of May. As long as we're talking about tornado outbreaks in the southern U.S., such as we've experienced this week, we don't have to worry about hurricane formation in the Gulf of Mexico. Tornado outbreaks require a stong jet stream, which is the bane of a hurricane trying to form.

The other missing ingredient--at least in the Caribbean and tropical Atlantic--has been the lack of an initial disturbance to get a hurricane started. Africa has just begun to produce its usual summer parade of tropical waves, which frequently serve as the nucleus for a tropical storm. These tropical waves are coming off of Africa at about 2 degrees North Latitude, which is too close to the Equator to allow a hurricane to spin up. I'm not expecting any tropical development for the rest of May in the Atlantic due to high wind shear and the lack of proper initial disturbances.

It's another story in the Eastern Pacific, where wind shear is less and the remains of an old cold front coming off of North America could serve to trigger tropical storm formation as early as next week. The hurricane specialists at the National Hurricane Center begin rotating shift work on Monday May 15, which marks the official beginning of the Eastern Pacific hurricane season.

My next blog will be on Monday. I'll talk about air pollution some next week, since May marks the beginning of air pollution season, and next week is EPA's Air Pollution Awareness Week.

Jeff Masters

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351. atmosweather 06:41 PM GMT del 13 Maggio 2006
Gotta run everyone, I'll be back later this evening. Member Since: Settembre 24, 2005 Posts: 33 Comments: 9265

352. ProgressivePulse 06:43 PM GMT del 13 Maggio 2006
Adios Rich Member Since: Agosto 19, 2005 Posts: 5 Comments: 4443

353. Levi32 06:45 PM GMT del 13 Maggio 2006
Talk to you later Rich! Member Since: novembre 24, 2005 Posts: 593 Comments: 25604

354. Levi32 06:45 PM GMT del 13 Maggio 2006
On visible you can see low clouds being drawn towards the center of the wave from the southwest. Member Since: novembre 24, 2005 Posts: 593 Comments: 25604

355. Levi32 06:55 PM GMT del 13 Maggio 2006
Um...guys? Look at where the NHC has the wave in 72 hours. Any fears? Member Since: novembre 24, 2005 Posts: 593 Comments: 25604

356. Levi32 06:58 PM GMT del 13 Maggio 2006
Oh my gosh look at this! Here are links to the GFS shear forecasts for 72, 96, and 120 hours. The shear just clears a path for the wave into the Caribbean!!! This is bad! 72 hour 96 hour 120 hour Member Since: novembre 24, 2005 Posts: 593 Comments: 25604

357. Levi32 07:01 PM GMT del 13 Maggio 2006
Oops, forgot 144 hours! Look at less than 5-8 knots of shear in the western Caribbean! Right where the wave will be! 144 hour shear Member Since: novembre 24, 2005 Posts: 593 Comments: 25604

358. HurricaneKing 07:09 PM GMT del 13 Maggio 2006
TROPICAL WAVES... A TROPICAL WAVE HAS BEEN RELOCATED ALONG 43W S OF 9N BASED UPON CYCLONIC TURNING EVIDENT ON SATELLITE IMAGERY. THIS NEW POSITION ALSO CONSIDERS CONTINUITY OF THE FORWARD SPEED OF THE WAVE OVER THE PAST COUPLE OF DAYS. IN ADDITION...THIS WAVE AXIS POSITION IS IN BETTER AGREEMENT WITH THE MODEL GUIDANCE. THE TROPICAL WAVE IS MOVING W NEAR 10 KT. SCATTERED MODERATE CONVECTION IS ALONG AND TO THE E OF THE AXIS EMBEDDED WITHIN THE ITCZ FROM 4N-8N BETWEEN 40W-43W. Member Since: Luglio 6, 2005 Posts: 71 Comments: 2432

359. weatherguy03 07:11 PM GMT del 13 Maggio 2006
Ok ST Jr. take it easy!..LOL First its only an open wave right now. Second, it needs to really gain some lattitude and it better do it fast! Third, the environment out ahead of this is very hostile. Very low chance of developing. Member Since: Luglio 5, 2005 Posts: 581 Comments: 29681

360. louastu 07:13 PM GMT del 13 Maggio 2006
I don't think it is going to develop much further, and even if it does, it will probably be no threat to the United States.

361. Levi32 07:15 PM GMT del 13 Maggio 2006
Bob, I just posted the shear forecasts and low shear opens up right in front of it! Also it is okay to be excited about the first wave of the season. It has been a long time since we have seen some action. Also, the NHC forecast chart I posted above shows it gaining latitude and entering the east Caribbean! Member Since: novembre 24, 2005 Posts: 593 Comments: 25604

362. HurricaneKing 07:16 PM GMT del 13 Maggio 2006
I didn't say it was going to develop. Member Since: Luglio 6, 2005 Posts: 71 Comments: 2432

363. weatherguy03 07:17 PM GMT del 13 Maggio 2006
Its cool Levi. I was just joking with ya! Enjoy it and get excited! Have a good day! Member Since: Luglio 5, 2005 Posts: 581 Comments: 29681

364. StellarCyclone 07:23 PM GMT del 13 Maggio 2006
Prayers for all - throughout the season! Looks like things are heating up ...

365. louastu 07:24 PM GMT del 13 Maggio 2006
To me, it looks like it will head towards Haiti.

366. Levi32 07:24 PM GMT del 13 Maggio 2006
I understand lol. We are all scared of the season. Thanks Bob have a good day yourself! Member Since: novembre 24, 2005 Posts: 593 Comments: 25604

367. Levi32 07:26 PM GMT del 13 Maggio 2006
Louastu why do you think it will head towards Haiti? I think the high will build back in and put it in the west Caribbean. Member Since: novembre 24, 2005 Posts: 593 Comments: 25604

368. Levi32 07:30 PM GMT del 13 Maggio 2006
I have to go for an hour or so. Catch you all later! Member Since: novembre 24, 2005 Posts: 593 Comments: 25604

369. louastu 08:10 PM GMT del 13 Maggio 2006
About 90% percent of this is a big guess. The other 10% is what I have learned (it is possible that I have learned the wrong way, or an outdated way). I think the 3 systems that are going to be responsible for steering the tropical wave are the 1019 mb high in the middle of the Atlantic, the 1009 mb low off the coast of Panama, and the 1010 mb low which is mostly off the map, with a front that extends into Mexico. If I am reading that map correctly, then the 1019 mb high is forecast to move off to the ESE. If this happens, it should allow a turn to the North. The 1010 mb low has a front that extends all the way to the Yucatan Peninsula, which if I am not mistaken (or misinformed), should help to cause a turn to the North. Finally, I believe the steering flow around the 1009 mb low will also aid in a Northward turn. If the 1009 mb low doesn't move then the wave should get pushed into Puertyo Rico, but I think it will push off to the West, which will allow the wave to make it a little further West before beginning it's Northward turn. This is my first true forecast. If I am wrong about something, or I have overlooked something, please let me know.

370. louastu 08:11 PM GMT del 13 Maggio 2006
Crap. I thought I posted that as a smaller image.

371. louastu 08:14 PM GMT del 13 Maggio 2006
"Puertyo Rico" should be "Puerto Rico".

372. snowboy 08:17 PM GMT del 13 Maggio 2006
I don't like the look or the outlook for the system out in the Atlantic. Look out if it survives and reaches the Caribbean. Member Since: Settembre 21, 2005 Posts: 10 Comments: 2546

373. StormJunkie 08:31 PM GMT del 13 Maggio 2006
Wave? Where? Who, what'd I miss. (pants briefly then begins looking for wave again) I will have to look in to this when I getting home tonight. Going ou o dinner with my girlfriend. See ya SJ Member Since: Agosto 17, 2005 Posts: 26 Comments: 15240

374. RL3AO 08:47 PM GMT del 13 Maggio 2006
Going ou o dinner with my girlfriend. See ya haha, you're such a comedian...wait, you're serious?

375. StormJunkie 08:50 PM GMT del 13 Maggio 2006
Yes, other then the typos I am serious:) out to Now this wave on the other hand, I don't know about. SJ Member Since: Agosto 17, 2005 Posts: 26 Comments: 15240

376. louastu 08:53 PM GMT del 13 Maggio 2006
On the map I posted, look South of 10 N, between 40 W and 50 W.

377. Levi32 08:54 PM GMT del 13 Maggio 2006
SJ you are still here? lol! You should have been gone by now. 20 minutes is plenty of time to check out the wave lol. When you say you are leaving, and then come back, how can we believe you lol. Member Since: novembre 24, 2005 Posts: 593 Comments: 25604

378. StormJunkie 08:57 PM GMT del 13 Maggio 2006
I am leaving levi, but still in the process of getting ready. I'll be gone in the next 20. Anywho where did this map come from, what do the model say, and had adiscussion mentioned it yet? SJ Member Since: Agosto 17, 2005 Posts: 26 Comments: 15240

379. Levi32 09:00 PM GMT del 13 Maggio 2006
SJ all you have to do to get all that is read all the above posts from the last few hours. This wave has circulation on satellite and NHC forecasts it to move into the Caribbean. The NHC discussion even notes the circulation, and I posted shear forecasts a while back that show the shear clearing ahead of the wave in the Caribbean. Member Since: novembre 24, 2005 Posts: 593 Comments: 25604

380. StormJunkie 09:00 PM GMT del 13 Maggio 2006
Sorry ya'll my typing is off today. I am leaving levi, but still in the process of getting ready. I'll be gone in the next 20. Anywho where did this map come from, what do the models say, and has a discussion mentioned it yet? SJ Member Since: Agosto 17, 2005 Posts: 26 Comments: 15240

381. louastu 09:02 PM GMT del 13 Maggio 2006
I got the map from the NHC. Link Click where it says "1200 UTC SURFACE ANALYSIS".

382. StormJunkie 09:03 PM GMT del 13 Maggio 2006
I will read all the info when i get home Levi, but thanks for the quick update. Find all the info here StormJunkie.com links and more. See ya SJ Member Since: Agosto 17, 2005 Posts: 26 Comments: 15240

383. Levi32 09:03 PM GMT del 13 Maggio 2006
That's ok SJ girls make you shaky lol. Member Since: novembre 24, 2005 Posts: 593 Comments: 25604

384. snowboy 09:06 PM GMT del 13 Maggio 2006
Thanks for the overview of the Atlantic louastu. If the system starts moving WNW and gaining latitude, the high SSTs and low shear environment will encourage further development. Member Since: Settembre 21, 2005 Posts: 10 Comments: 2546

385. pt100 09:09 PM GMT del 13 Maggio 2006
Hi, I dont agree that this is something of importance. What I see on the visible, on 43W, 4N, is a low local cloud forming due to local circumstances. Because this cloud is formed, a vacuum is created on the west side of it. I don't know if this happens because the cloud itsself redirects the wind or because watervapor turns to little droplets creating a vacuum. The "wave" you see is the passing clouds filling up this vacuum on 47W, 3N

386. louastu 09:09 PM GMT del 13 Maggio 2006
I am not sure about that. If it is interacts with the front, then I think it will strip the system of most of it's moisture (kind of like what happened with Tammy last year).

387. Levi32 09:19 PM GMT del 13 Maggio 2006
pt100, if you are right, then how do you explain the NHC taking note of it calling it a wave and saying it has circulation. Are you saying they are wrong? Member Since: novembre 24, 2005 Posts: 593 Comments: 25604

388. pt100 09:22 PM GMT del 13 Maggio 2006
Im not very skilled in weather but Ive looked into this very intens, plz look for yourself especialy what happens in the lower atmos.visible

389. Levi32 09:29 PM GMT del 13 Maggio 2006
pt100, I don't think I totally understand what you were talking about, but look at about 47w and 5n on your loop. See the circulation? The area of convection to its east is the wave itself. If the wave moves ontop of that circulation, we will have a tropical low on our hands. That is definately a full blown tropical wave. Member Since: novembre 24, 2005 Posts: 593 Comments: 25604

390. TheLuckyTacoBlizzard 09:36 PM GMT del 13 Maggio 2006
Levi32 where would this be going if this did pop up in to a TD or stonger if you come to my blog there some in i think you sould see

391. Levi32 09:40 PM GMT del 13 Maggio 2006
David it is hard to tell where it would go after formation since we are so far away from that time. My guess right now would be anywhere from the Yucatan Peninsula to western Cuba. Member Since: novembre 24, 2005 Posts: 593 Comments: 25604

392. TheLuckyTacoBlizzard 09:42 PM GMT del 13 Maggio 2006
and may be FL or some where in the gulf

393. pt100 09:45 PM GMT del 13 Maggio 2006
I agree with that, what im saying is that this is because on 44W, 3-4N a cloud is formed. To my opinion its just a little low behind this cloud and this circulation will be blown into peaces within a couple of hours

394. pt100 09:50 PM GMT del 13 Maggio 2006
or is it pieces?

395. louastu 09:52 PM GMT del 13 Maggio 2006
It is pieces.

396. snowski 09:57 PM GMT del 13 Maggio 2006
SSD is showing Chanchu loop:

397. Levi32 09:58 PM GMT del 13 Maggio 2006
Well you just described what a wave is. A small trough behind some convection. If you think it will fall apart soon that is fine with me. I think it is more than you make it out to be though. Member Since: novembre 24, 2005 Posts: 593 Comments: 25604

398. snowski 09:58 PM GMT del 13 Maggio 2006
That's: http://www.ssd.noaa.gov/mtsat/wpac/loop-ir2.html

399. pt100 10:05 PM GMT del 13 Maggio 2006
Levi, what im interrested in is why that local cloud formed, I looked at the map but its all water over there. Is it sst or is it pressure. or a combination of the 2. Can you tell?

400. Levi32 10:11 PM GMT del 13 Maggio 2006
So you are talking about one small area of cloud? You are not talking about the whole wave? If that is the case, then there is no way to really know how one little cloud formed. The air probably just got unstable, a thermal broke the cap and up puffed an area of thunderstorms. Member Since: novembre 24, 2005 Posts: 593 Comments: 25604

401. louastu 10:15 PM GMT del 13 Maggio 2006
I have to go out for a little bit. I should be back within a few hours.

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