Invest 91L more organized, but has little time to develop

By: Dr. Jeff Masters , 2:31 PM GMT on April 22, 2011

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Hurricane season is more than a month away, but we have a tropical disturbance (91L) typical of what one might see in June or November. 91L is spinning over the waters a few hundred miles south of Bermuda, and has improved considerably in organization since yesterday, thanks to a drop in wind shear. The latest SHIPS model output is showing shear of 40 - 55 knots over 91L, but shear analyses from the University of Wisconsin CIMSS group is showing lower shear values of 20 - 30 knots over the main circulation center and to 91L's north, where the heaviest thunderstorms are. The system has a warm core at low levels, but a trough of low pressure lies over the storm at upper levels, and this trough is pumping cold, dry air into 91L, making it not completely tropical. One characteristic of subtropical systems like 91L is the presence of the main band of heavy thunderstorms removed several hundred miles from the circulation center, and 91L fits that description. 91L has two centers of circulation competing to be dominant, and this competition is slowing the storm's development. The storm was headed north at 5 - 10 mph early this morning, but that motion has halted, and 91L appears to be moving more south-southwesterly now, away from Bermuda. Sea surface temperatures are 23°C, which are very cold for a tropical storm to form in, but could support development of a subtropical storm.

As 91L moves south today, shear will steadily rise, and the storm likely has only until Friday night before shear grows too high to permit development. NHC is giving 91L a 20% chance of developing into a subtropical or tropical depression, which is a reasonable forecast. There has been only been one named April storm in the Atlantic since 1851, Tropical Storm Ana of 2003. The formation of a tropical disturbance at this location this time of year is unusual, but is not a harbinger of a active season ahead. Had this been going on in the Caribbean, that would be a different story.


Figure 1. Morning satellite image of the Atlantic tropical disturbance 91L. Note the two centers of circulation competing to be dominant. I expect the northern center will become dominant.

Jeff Masters

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I have to go ...I just wanted to say Wuzup Gro..!
Member Since: September 27, 2007 Posts: 1 Comments: 20910
Quoting PlazaRed:
Toche!!
Or whatwever they say in thr tounge of the Franks?


At least they are holding swords when they say. Most here are unarmed.
Member Since: July 17, 2009 Posts: 71 Comments: 25968
Quoting PlazaRed:
I do apologise for getting a bit 'irate,' earlier and having to come yet again to terms with the fact that some of us are 'human,'
The fact is that the world as we have 'known,' it is about to go through a phase of transience and there is nothing we can do to reverse its path.
All I/we can be thankful for is that we can perceive that change is inevitable.
Apologies to Hydrus!!





No apology needed P.R..You would have to read back many posts to fully understand what really transpired..Nobody was gonna hit anyone. It was a harmless joke that I should not have taken so seriously.....I learned something today...:)
Member Since: September 27, 2007 Posts: 1 Comments: 20910
The Dry Dragon:



has 91L in its paw
Member Since: July 12, 2007 Posts: 0 Comments: 6004
351. CaicosRetiredSailor
12:54 AM GMT on April 23, 2011
How do they rate? I or not I
Member Since: July 12, 2007 Posts: 0 Comments: 6004
350. Grothar
12:54 AM GMT on April 23, 2011
Quoting GeoffreyWPB:
Good evening Grothar.


Hey, Geoff. Anything new happen while I was gone. Heard there was a big swirl in the Atlantic. Heard those NHC guys weren't doing their job again.
Member Since: July 17, 2009 Posts: 71 Comments: 25968
349. PlazaRed
12:53 AM GMT on April 23, 2011
Toche!!
Or whatwever they say in thr tounge of the Franks?
Member Since: January 21, 2011 Posts: 0 Comments: 2072
348. Grothar
12:51 AM GMT on April 23, 2011
Quoting PlazaRed:
Como estas Amigo?
Toda las cosas eestan bien y usted esta como siempre, predido!
Where on Earth-y have you been hiding Senor Grother? When we have had a very interesting day!!


Achenando! Watching everybody being irate.
Member Since: July 17, 2009 Posts: 71 Comments: 25968
346. PlazaRed
12:49 AM GMT on April 23, 2011
Como estas Amigo?
Toda las cosas eestan bien y usted esta como siempre, predido!
Where on Earth-y have you been hiding Senor Grother? When we have had a very interesting day!!
Member Since: January 21, 2011 Posts: 0 Comments: 2072
345. hydrus
12:49 AM GMT on April 23, 2011
Quoting KEEPEROFTHEGATE:
models are for guidance things can and will change hopefully

sorry your house is getting beat up would you prefer if it just blew away
No...I like my house and would like to keep it. I lost 2 houses to Charley. This one is repairable if it would just stop fricken raining....:)
Member Since: September 27, 2007 Posts: 1 Comments: 20910
344. GeoffreyWPB
12:47 AM GMT on April 23, 2011
Live St. Louis TV Coverage
Member Since: September 10, 2007 Posts: 0 Comments: 11099
343. melwerle
12:46 AM GMT on April 23, 2011
Glad I'm here in Sandy Eggo...hubby had to fly back to Georgia...he said it's humid and raining...

I'm sitting on the porch with a chardonney in 70 degree weather...sunshine and cool...

Cheers...
Member Since: June 28, 2006 Posts: 12 Comments: 1837
342. GeoffreyWPB
12:45 AM GMT on April 23, 2011
Good evening Grothar.
Member Since: September 10, 2007 Posts: 0 Comments: 11099
340. CaicosRetiredSailor
12:44 AM GMT on April 23, 2011
If Dr. Masters is home in Ann Arbor... actually when I investigated closer, not as much WX in that area as I first thought there might be. My brother lives at Lake Whitmore just N. of Ann Arbor, so I watch that area.
Member Since: July 12, 2007 Posts: 0 Comments: 6004
339. Grothar
12:40 AM GMT on April 23, 2011
Hello.
Member Since: July 17, 2009 Posts: 71 Comments: 25968
338. emcf30
12:33 AM GMT on April 23, 2011
Confirmed Tornado on ground. Heading toward St Louis metro
Member Since: August 7, 2010 Posts: 0 Comments: 1933
337. KEEPEROFTHEGATE (Mod)
12:31 AM GMT on April 23, 2011
Member Since: July 15, 2006 Posts: 170 Comments: 53485
336. emcf30
12:30 AM GMT on April 23, 2011
Keeper you crack me up.
Member Since: August 7, 2010 Posts: 0 Comments: 1933
335. PlazaRed
12:28 AM GMT on April 23, 2011
I do apologise for getting a bit 'irate,' earlier and having to come yet again to terms with the fact that some of us are 'human,'
The fact is that the world as we have 'known,' it is about to go through a phase of transience and there is nothing we can do to reverse its path.
All I/we can be thankful for is that we can perceive that change is inevitable.
Apologies to Hydrus!!





Member Since: January 21, 2011 Posts: 0 Comments: 2072
334. KEEPEROFTHEGATE (Mod)
12:28 AM GMT on April 23, 2011
Quoting emcf30:
Big hail

2335 400 BIG SPRING MONTGOMERY MO 3880 9148 NUMEROUS BASEBALL TO GRAGEFRUIT SIZE HAILSTONES (LSX)


Member Since: July 15, 2006 Posts: 170 Comments: 53485
333. GeoffreyWPB
12:26 AM GMT on April 23, 2011
...SPECIAL FEATURE...

A 1008 MB NON-TROPICAL LOW CONTINUES TO SPIN ABOUT 430 NM S OF
BERMUDA NEAR 27N64W. SHOWER ACTIVITY HAS NOT INCREASED FROM
EARLIER TODAY WITH A SMALL AREA OF SHOWERS/POSSIBLE
THUNDERSTORMS S OF THE CENTER FROM 25N-26N BETWEEN 64W-65W...AND
SCATTERED SHOWERS/ISOLATED THUNDERSTORMS WITHIN 75 NM N AND E OF
A SURFACE TROUGH EXTENDING FROM THE LOW CENTER ALONG 27N62W
25N60W 21N62W 19N65W. E WINDS UP TO 30 KTS ARE N OF THE SYSTEM
WITH 20-25 KT WINDS ELSEWHERE AROUND THE LOW CENTER AND TROUGH.
WATER VAPOR IMAGERY INDICATES A DRY SLOT OF AIR BEING SUCKED
AROUND THE SRN SEMI-CIRCLE OF THE STORM. THIS DRY AIR INTRUSION
ALONG WITH UNFAVORABLE UPPER LEVEL WINDS ARE EXPECTED TO HINDER
FURTHER DEVELOPMENT. THE SYSTEM IS CURRENTLY MOVING WSW AT 9KT.
A GENERAL SW MOTION IS EXPECTED OVER THE NEXT COUPLE OF DAYS.
Member Since: September 10, 2007 Posts: 0 Comments: 11099
332. emcf30
12:25 AM GMT on April 23, 2011
Big hail

2335 400 BIG SPRING MONTGOMERY MO 3880 9148 NUMEROUS BASEBALL TO GRAGEFRUIT SIZE HAILSTONES (LSX)
Member Since: August 7, 2010 Posts: 0 Comments: 1933
331. KEEPEROFTHEGATE (Mod)
12:25 AM GMT on April 23, 2011
Quoting hydrus:
Big giant red blob right over my beat up house...Lovely...
models are for guidance things can and will change hopefully

sorry your house is getting beat up would you prefer if it just blew away
Member Since: July 15, 2006 Posts: 170 Comments: 53485
329. hydrus
12:11 AM GMT on April 23, 2011
Quoting KEEPEROFTHEGATE:
Big giant red blob right over my beat up house...Lovely...
Member Since: September 27, 2007 Posts: 1 Comments: 20910
328. KEEPEROFTHEGATE (Mod)
12:06 AM GMT on April 23, 2011
Member Since: July 15, 2006 Posts: 170 Comments: 53485
327. hydrus
12:05 AM GMT on April 23, 2011
Quoting emcf30:
Now that is a nasty looking tornado on that link
Here is one of my favorite tornado films ever.. From back in 1953, Warner Robbins AFB..Link
Member Since: September 27, 2007 Posts: 1 Comments: 20910
326. KEEPEROFTHEGATE (Mod)
11:59 PM GMT on April 22, 2011
Member Since: July 15, 2006 Posts: 170 Comments: 53485
325. KEEPEROFTHEGATE (Mod)
11:58 PM GMT on April 22, 2011
XX/INV/91L
MARK
24.95N/63.76W
Member Since: July 15, 2006 Posts: 170 Comments: 53485
324. hydrus
11:57 PM GMT on April 22, 2011
This looks like a really large tornado...Which it is.
Member Since: September 27, 2007 Posts: 1 Comments: 20910
323. emcf30
11:56 PM GMT on April 22, 2011
Now that is a nasty looking tornado on that link
Member Since: August 7, 2010 Posts: 0 Comments: 1933
322. hydrus
11:55 PM GMT on April 22, 2011
Quoting emcf30:
Hydrus, Ref #318, Do you know where that pic is from?
That was heavy tornado damage in Chapman, Kansas on June 11, 2008...Link
Member Since: September 27, 2007 Posts: 1 Comments: 20910
321. emcf30
11:50 PM GMT on April 22, 2011
Hydrus, Ref #318, Do you know where that pic is from?
Member Since: August 7, 2010 Posts: 0 Comments: 1933
320. PlazaRed
11:49 PM GMT on April 22, 2011
Please Note:- We could get banned for posting rubbish like this and I don't want to activate the banner so ''calm down,'' as we at best have a responsibility to humanity to behave in a calm and acceptable way towards those who quest after knowledge?
Member Since: January 21, 2011 Posts: 0 Comments: 2072
319. GeoffreyWPB
11:48 PM GMT on April 22, 2011
Live TV Coverage from Tulsa
Member Since: September 10, 2007 Posts: 0 Comments: 11099
318. hydrus
11:46 PM GMT on April 22, 2011
ouch
Member Since: September 27, 2007 Posts: 1 Comments: 20910
317. hydrus
11:44 PM GMT on April 22, 2011
Quoting PlazaRed:

How I wish I had you as a drinking partner in the years of my youth!
For we could have wasted each other and told the world it was in a good cause?
Man!! take the quest by the hand and do not dally with the wraiths who have trodden this land be 4 for the hand of the inevitable is in the mind of the invincible!
Power perceived is power achieved P.R...:)
Member Since: September 27, 2007 Posts: 1 Comments: 20910
316. hydrus
11:40 PM GMT on April 22, 2011
Another rather scary looking June example..
Member Since: September 27, 2007 Posts: 1 Comments: 20910
315. PlazaRed
11:39 PM GMT on April 22, 2011
Quoting hydrus:
. The only punch I have has 11 bottles of grain alcohol in it..I am concerned about how much severe weather we may face early next week......More may be required around that time..

How I wish I had you as a drinking partner in the years of my youth!
For we could have wasted each other and told the world it was in a good cause?
Man!! take the quest by the hand and do not dally with the wraiths who have trodden this land be 4 for the hand of the inevitable is in the mind of the invincible!
Member Since: January 21, 2011 Posts: 0 Comments: 2072
314. hydrus
11:38 PM GMT on April 22, 2011
Quoting KEEPEROFTHEGATE:
ya been active kinda reminds me of 05 and we still got all of may yet thats when things really get going we even get in on the events then
Even june has some nasty tornady outbreaks. Here is one from June 18 of last year via WIKI..
Member Since: September 27, 2007 Posts: 1 Comments: 20910
313. hydrus
11:35 PM GMT on April 22, 2011
This image looks familiar....I have seen this before...hmmmmm oh yeah, like for the past 2 months..
Member Since: September 27, 2007 Posts: 1 Comments: 20910
312. KEEPEROFTHEGATE (Mod)
11:35 PM GMT on April 22, 2011
Quoting hydrus:
This is turning out to be a very active Spring...And there is a lot of it left.
ya been active kinda reminds me of 05 and we still got all of may yet thats when things really get going we even get in on the events then
Member Since: July 15, 2006 Posts: 170 Comments: 53485
311. emcf30
11:34 PM GMT on April 22, 2011
I hope Reed gets on a tornado before dark he will have some great shots. This is his first storm of the year in the Dominator. Will be able to get up close now.
Member Since: August 7, 2010 Posts: 0 Comments: 1933
310. hydrus
11:31 PM GMT on April 22, 2011
Quoting KEEPEROFTHEGATE:
This is turning out to be a very active Spring...And there is a lot of it left.
Member Since: September 27, 2007 Posts: 1 Comments: 20910
308. emcf30
11:29 PM GMT on April 22, 2011
Member Since: August 7, 2010 Posts: 0 Comments: 1933
307. KEEPEROFTHEGATE (Mod)
11:29 PM GMT on April 22, 2011
Member Since: July 15, 2006 Posts: 170 Comments: 53485
306. hydrus
11:27 PM GMT on April 22, 2011
Quoting emcf30:
Wow...You can actually see the overshooting tops on those super-cells....Really cool pic.
Member Since: September 27, 2007 Posts: 1 Comments: 20910
305. emcf30
11:24 PM GMT on April 22, 2011
Member Since: August 7, 2010 Posts: 0 Comments: 1933

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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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