High wind shear over the Gulf of Mexico

By: Dr. Jeff Masters , 2:01 PM GMT on May 26, 2006

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April 2006 was the warmest April on record in the U.S. since record keeping began in 1895. The U.S. has now had two "warmest ever" months this year, January and April. The nationally averaged April temperature was 56.5F (13.6C), which was 4.5F (2.5C) above the 1901-2000 (20th century) mean. Globally, April ranked as the 7th warmest April on record, and the period January through April ranks as the 6th warmest such period on record globally. From Figure 1, we can see that the entire tropical Atlantic region where hurricane formation occurs was warmer than average during April, and this region has remained about .5 - 1.5 degrees C above normal over the past few months.


Figure 1. Temperature Anomalies (difference of temperature from normal) for April 2006.

With all this warmer than normal water over the Atlantic, one might expect that hurricane season could have an earlier than normal start. However, that will not be the case this year, because high levels of wind shear will dominate the regions where June tropical cyclones typically form--the Gulf of Mexico. The Gulf is the primary genesis region in June because that is typically the only region where we get initial disturbances that can set a tropical storm spinning up. These initial disturbances in June are usually the remains of an old cold front or upper-level trough that stalls out over the Gulf and festers for a few days, gradually developing deep convection and spinning up into a tropical depression. June is too soon to get a tropical storm in the Caribbean or tropical Atlantic, since the tropical waves that typically serve as the initial seed for a storm are still too far south. The tropical waves coming off of Africa right now are at about six degrees latitude, and they need to be at nine degrees latitude or higher before they are far enough from the equator to serve as a seed for a tropical storm.

For the start of this year's hurricane season next week, the GFS model (Figure 2) is forecasting that there will be strong upper-level winds over the Gulf of Mexico. These winds are part of the so-called Subtropical jet stream. The jet stream--the band of high velocity winds that circles the globe--always has at least one branch, the polar jet. As its name implies, the polar jet lies close to the pole, and circles it entirely. Sometimes the jet splits, and a branch called the Subtropical jet blows across subtropical latitudes, where the Gulf of Mexico lies. As we can see from the GFS forecast for June 3 in Figure 2, both the polar and subtropical jets are apparent where the color coding indicates strong winds at the 300 millibar level (the jet stream occurs at an altitude in the atmosphere where the pressure ranges between 300 mb and 200 mb). The strong winds of the Subtropical jet will create too much wind shear for a tropical storm to form in the Gulf of Mexico next week, and the jet is expected to remain strong for at least the next two weeks. So, an early start to hurricane season looks unlikely this year.


Figure 2. GFS forecast for June 3 2006 at 300 millibars, the altitude where the jet stream is found. The polar and subtropical branches of the jet stream are clearly visible where upper-level wind speeds are highest. An area of light upper level winds and low wind shear is forecast to develop over the southern Caribbean Sea.

What about the southern Caribbean Sea, where the GFS model is predicting very light upper level winds, and where wind shear is likely to be low? Well, we will have to watch this area for tropical storm formation, but as I indicated before, the tropical waves one needs to act as the seed for a storm are usually too far south in June. Tropical waves usually do not start entering the Caribbean until July.

Have a worry-free weekend, everyone!

Jeff Masters

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278. 53rdWeatherRECON
3:46 PM GMT on May 31, 2006
Array_B

Array_B
Member Since: August 5, 2005 Posts: 2 Comments: 80
277. TampaSteve
3:00 PM GMT on May 30, 2006
So...how is AlettEpsilon doing? :)
276. MarcKeys
1:15 PM GMT on May 30, 2006
Sounds like good news so far. Hopefully these winds will continue and make this year better than the last 3.
a href="Florida Keys Fishing" target="_blank">Link
275. newt3d
12:50 PM GMT on May 30, 2006
Yeah, looks like Aletta has come back from the grave. Not that it's going to do much now that it's back ... but neat anyway.
Member Since: October 6, 2005 Posts: 0 Comments: 90
274. fredwx
12:42 PM GMT on May 30, 2006
I tend to agree that the solar cycle does influence the earth's weather and there is evidence that the global temperature is related to the length of that cycle and number of sunspots.
See Solar Link


I still think that the 90% hit risk is much to high.
Member Since: June 8, 2005 Posts: 221 Comments: 261
272. fredwx
12:30 PM GMT on May 30, 2006
I give up - the WUBA system is changing the link so I will just post it here directly

http://www.e-transit.org/hurricane/welcome.html
Member Since: June 8, 2005 Posts: 221 Comments: 261
271. fredwx
12:28 PM GMT on May 30, 2006
One more try

United States Landfalling Hurricane Probability Project
Member Since: June 8, 2005 Posts: 221 Comments: 261
270. fredwx
12:26 PM GMT on May 30, 2006
Sorry, Here is the correct link for the United States Landfalling Hurricane Probability Project
Member Since: June 8, 2005 Posts: 221 Comments: 261
269. fredwx
12:23 PM GMT on May 30, 2006
TOL MichaelSTL
RE Hurricane Risk
I think that predictions of 90% risk is misleading and counterproductive. If you look at Dr. Gray and company's outlook: United States Landfalling Hurricane Probability Project there is only a 40% of at least a tropical storm for the same region. I don't know why the big difference but I would doubt the 90% risk claim.

Note: Dr. Gray's outlook is scheduled to be updated on Wednesday.

Member Since: June 8, 2005 Posts: 221 Comments: 261
268. acduke
12:23 PM GMT on May 30, 2006
Yeah, they say in the discussion on Aletta that they expect her to die off to a remnant low, so if she doesn't, then we'll know that we're still in the "all bets are off" mode when it comes to predicting tropical systems this year.
266. WSI
12:06 PM GMT on May 30, 2006
Here is the current shear in the Gulf. As of 5/30, there is too much shear for favorable tropical development.
265. WSI
10:54 AM GMT on May 30, 2006
They mention the system in the western gulf in the tropical discussion, but that is about it. They just mentioned it, and didn't really say much about it. Shear unfavorable in the area as well. franck, where are you getting your shear information? I still show the shear to be high there.
264. acduke
10:46 AM GMT on May 30, 2006
I thought this seemed fitting...

May 29, 2006, 10:37PM
Study finds global warming may worsen poison ivy

Associated Press

WASHINGTON - Another reason to worry about global warming: more and itchier poison ivy.

The noxious vine grows faster and bigger as carbon dioxide levels in the atmosphere rise, researchers reported on Monday.

And a carbon dioxide-driven vine produces more of its rash-causing chemical, urushiol, concluded experiments conducted in a forest at Duke University where scientists increased carbon dioxide levels to those expected in 2050.

(Continue Article)

Haha, I didn't know Duke University had a forest? I wish Missouri State University had a forest. Our mascot is the Bear, you know. I bet you Blue Devils don't live in the forest.
263. franck
7:56 AM GMT on May 30, 2006
Yes, there is some circulation to that thing off Texas. Water is hot, and there isn't much shear. By mid-day it may be interesting.
Member Since: August 30, 2005 Posts: 0 Comments: 1150
262. pearlandtx
4:53 AM GMT on May 30, 2006
I've been watching the weather on the Tx coast for years and this seems like a weird set-up. Most large rain systems have some sort of movement passing through. This one is just hanging out with no real direction.
261. ForecasterColby
4:46 AM GMT on May 30, 2006
There's no low yet. However, there's a very high amount of instability in the air, so one might form.
260. WSI
4:10 AM GMT on May 30, 2006
"Any thoughts on this mess off the Texas coast?"

Well, I am no professional, but here is what I see. There is really no low level circulation with the system at all. In fact, even the upper level winds look disorganized. The shear in the area is still pretty hostile. Also, none of the models that I can see have picked up on anything down there.

None of this is to say it won't do something later on.

Now it's late, so if I missed something someone kick me in the tail, LOL!
259. pearlandtx
4:01 AM GMT on May 30, 2006
Any thoughts on this mess off the Texas coast? It sure seems to be just sitting there. We had some serious rains (13" in places) from this system earlier today before it moved off over the Gulf. The local weather guesser hinted on the 10 o'clock news that "something could be happening out there".
257. ForecasterColby
3:22 AM GMT on May 30, 2006
The odds aren't great...but it is looking very subtropical at the moment. Worth watching.
256. acduke
2:55 AM GMT on May 30, 2006
Savannah,

It looks like its moving south so it wouldn't affect the U.S. Also there is too much dry air on the western side, and even if it could overcome that, it would run into the higher shear in northern Cuba and be recurved out to sea and torn apart. That's what I see anyway...thoughts anyone?
255. SavannahStorm
2:37 AM GMT on May 30, 2006
Anyone have any insights on the cyclone east of GA/FL? The circulation shows up much tighter on the water vapor loop than it did earlier today.
Member Since: September 22, 2005 Posts: 18 Comments: 2342
254. ForecasterColby
2:02 AM GMT on May 30, 2006
It was the final *public* advisory - in the pacific they are only issued when land is theatened. I agree that Aletta is dead now, but she wasn't at the advisory time.
253. louastu
1:53 AM GMT on May 30, 2006
you can't really even see where Aletta is

I think you mean "was". The final advisory is only issued to tell you that the storm is dead.
251. louastu
1:41 AM GMT on May 30, 2006
It's ok. Hurricane Bud shouldn't be too far away. I want to see a sub-900 mb hurricane in the EPAC this year (as long as it doesn't hit land). The strongest EPAC hurricane ever was Hurricane Linda of 1997, with a minimum central pressure of 902 mb, and winds of 185 mph.
249. IKE
1:35 AM GMT on May 30, 2006
Looking at that satellite....forget what I just asked. She's a goner.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
248. IKE
1:34 AM GMT on May 30, 2006
"This will be the last public advisory on Aletta issued by the
National Hurricane Center."....

Why??
Member Since: June 9, 2005 Posts: 23 Comments: 37858
246. ancienttiger
1:29 AM GMT on May 30, 2006
Look to Univ of Colorado for Dr. Wm Gray et al. He has been the lead guy for around 20 yrs. and generally it pretty acurate. It seems all other "forecasts" are spin offs from Gray. Go to the source guys, you'll learn more.
245. louastu
1:27 AM GMT on May 30, 2006
There is a new invest in the Indian Ocean.

244. Alec
1:09 AM GMT on May 30, 2006
Even the NOAA says in their 2006 hurricane season prediction that it is extremely hard and virtually impossible to localize where they think hurricanes may make landfall this season this far out.......
243. RL3AO
1:01 AM GMT on May 30, 2006
When a hurricane does finally ride up the coast again, Joe Bastardi will act like the smartest guy on earth. Hey Joe, even a broken clock is right twice a day!
242. Alec
12:50 AM GMT on May 30, 2006
In general the Central Gulf coasts are usually high risk areas because as hurricanes get on the SW periphery of the Bermuda High once in the Gulf they tend to curve northwest and even north(assuming the high isn't spread out as an extended ridge over the northern Gulf and FL)
241. weatherguy03
12:49 AM GMT on May 30, 2006
I would definately agree with NOAA! Listen to the people with some REAL knowledge!..LOL
Member Since: July 5, 2005 Posts: 592 Comments: 29704
239. Hellsniper223
12:39 AM GMT on May 30, 2006
hehe... What a fricken joke. Hes only doing that crap to scare people into registering for accuweather.
Member Since: March 28, 2006 Posts: 0 Comments: 16
238. cjnew
12:17 AM GMT on May 30, 2006
Earlier today, I was watching CNN I think? anyways...

Joe Bastardi was on their saying how he feared for the north east U.S.
He had a 'nifty' little map highlighting areas as. low, med, high, very high. for hurricane landfall risk.
the only "LOW" area was the NE GOM, The "HIGH" areas were texas, south Fla.,and alot of the eastern sea board. then he had New York City (and surrounding areas) Higlithed as "VERY HIGH" and also N. carolina....

The rest of the spaces were filled with "med"
Member Since: July 22, 2005 Posts: 84 Comments: 2779
237. swlaaggie
11:49 PM GMT on May 29, 2006
Rain all day in sw louisiana. Soaked and loving it. It's about time.
Member Since: April 26, 2006 Posts: 0 Comments: 1032
236. Tazmanian
10:24 PM GMT on May 29, 2006
i am not feeling well to day and i am under the weather as well so when i get done with my showrs i am going to get some sleep so i may not be back on today when i get done with my shower that i need to do so this is my last post for today


sorry all if i am not a around a lot today to post i am off for the day see you when i get well and sorry for all of that
Member Since: May 21, 2006 Posts: 5091 Comments: 115073
235. Skyepony (Mod)
8:53 PM GMT on May 29, 2006
Yep, ENSO has gone neutral, like last season. The west side of the gulf should have some high shear kicking for days & it's already lossing convection from this morning. Looked neat lastnight like it was sucking energy from Aletta. East of fl looks to be trying desteratly to wrap around, shear is dropping a little in the area (& staying high over SE U.S., but i don't give it much a chance if any, just interesting.
Member Since: August 10, 2005 Posts: 162 Comments: 37829
234. Inyo
7:46 PM GMT on May 29, 2006
I dont see any La Nina or El Nino

Member Since: September 3, 2002 Posts: 42 Comments: 873
232. Caymanite
4:35 PM GMT on May 29, 2006
Happy memorial day to all of the American bloogers here. May you all have a very enjoyable and peaceful day with your families.
Member Since: December 9, 2005 Posts: 0 Comments: 315
231. Alec
4:33 PM GMT on May 29, 2006
Looks like a cool stream of water is making a comeback in the Eastern Pacific just South of the recent 30+ SST region! link
230. SavannahStorm
4:30 PM GMT on May 29, 2006
While the East Coast strom has a weak signature on visible and IR, the Link water vapor loop shows a different story.
Member Since: September 22, 2005 Posts: 18 Comments: 2342
228. weatherhunter
4:05 PM GMT on May 29, 2006
Do you mean the western Gulf? Link


I belive he means the one to the east of FL

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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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