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Atlantic Invest Thread 2011

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This thread is for discussing invests as and when they form.

90L has formed near Europe

20110310.1654.f15.x.85h.90LINVEST.30kts-1002mb-337N-182W.38pc.jpg

90Q south Atlantic

20110310.1900.msg2.x.ir1km.90QINVEST.25kts-1007mb-190S-390W.100pc.jpg

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Wow, this is early.

South Atlantic invest looks rubbish though, however the North Atlantic invest could well become sub-tropical though it is doubtful.

Just to give my opinion, this season will feature the main action late in the season and will be a below average season with 8/5/1. I will update this prediction and give an official forecast on June 15th. Very pleased with last season as i predicted 20/10/5 and the actual result was 18/10/5. I also got the 2007 hurricane season, spot on.

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90L is looking very impressive and has done over the last day or so. The circulation is well defined and winds are at 30kts near the centre. Small shot at becoming a subtropical storm but the system will probably push northeastwards towards Spain over colder water instead.

So, 90Q in the South Atlantic. These disturbances/storms seem to be happening more and more in the South Atlantic (though still very rare), with the formation of Tropical Storm Anita last year in March and an unnamed subtropical storm in November. Interestingly, GFS seems keen on developing 90Q subtropically or tropically, forcasting it to move away from the coast and strengthen. Waters are warm enough and there seems to be a pocket of unusually low shear in the area so 90Q may become one of the South Atlantic's rare tropical cyclones.

Interesting notes from Wikipedia regarding the last couple of years in the South Atlantic (with references to Anita):

Brazilian meteorologists stated that the formation of this storm and its transition into a tropical cyclone could be regarded as "historic". Tropical cyclone formation in the Atlantic Ocean south of the equator is extremely rare, with only seven other documented cyclones forming in this region in history. Although a minor system, it marked the first time that a tropical or subtropical system formed in consecutive years, following a subtropical storm in January 2009.[9] After the formation of a subtropical cyclone in November, 2010 marked the first year in recorded history that two tropical or subtropical systems had formed.

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Why it isn't named?Warm core,thunderstorms near center,closed circulation and 40 mph winds.

post-15004-0-40099400-1303460262_thumb.j

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Remnants of invest 91L reached Bahamas and brought some showers.Remnants will continue to Florida and possibly bring 1 inch of rain.

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Not long to go now before the season kicks off, SST's in the GOM now widely 27C to 30C and perhaps more crucially SST's around Cape Verde have reached 26C. Here is a live loop for us all to keep an eye on...

ir4-l.jpg

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Have to admit I was looking for an early start to the season maybe something in late May, but now I think this is likely to not be the case, the ITCZ is still at something like 2-3 degrees north when we really want it at 5-7 degrees as a minimum IMO.

SSTs are improving nicely but again a degree or 2 off from where they ideally need to be. We'll get there though. !

post-6326-0-09814200-1305287434_thumb.gi

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A later start to the season would probably be very welcome in the US, given the flooding that's going on at the moment and the devastating tornado outbreak in late April.

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Yes,the ITCZ position is the main factor.Even with strong shear and marginal SSTs some storms will form if the ITCZ is nough far from equator.

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ITCZ is still incredibly far south, below the equator at one point which is almost unheard of for this time of year.

We really need the pattern change to kick in and send it north, however I believe that's due to happen begining of June so we *might* start to see some good waves etc forming from mid June onwards.

post-6326-0-92152400-1306163882_thumb.gi

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Worth watching the next MJO wave as it rolls through the W.Caribbean in 2-3 weeks or so, that'll probably be the best shot at getting 'early'...otherwise we'll probably have to try our luck with these cut-off lows that attempt to become warm cored, abit like we have with 92L right now.

To be honest I suspected a fairly average start to the season, esp on the back of a fairly strong La Nina winter...with that being said I think with the quick shift towards warm neutral/weak El Nino occuring right now, I may have slightly under-estimated the chances of an early season system.

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Convection has pretty much diminshed from 92L this evening. The circulation still looks good but convection needs to come back soon if further development is to occur. High shear is really preventing further organisation of 92L at present.

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92L looks totally sheared now, I doubt it will get going again with the shear not forecast to abate significantly in the next few days.

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This is the output from UK Met and NOAA

Met O forecast

Our forecast for the 2011 season is for 13 tropical storms between June and November, with a 70% chance that the number will be in the range 10 to 17, which is very close to the 1980-2010 long-term average of 12. This is in contrast to 2010 which had a total of 19 tropical storms.

And the American forecast

Across the entire Atlantic Basin for the six-month season, which begins June 1, NOAA is predicting the following ranges this year:

• 12 to 18 named storms (winds of 39 mph or higher), of which:

• 6 to 10 could become hurricanes (winds of 74 mph or higher), including:

• 3 to 6 major hurricanes (Category 3, 4 or 5; winds of 111 mph or higher)

Each of these ranges has a 70 percent likelihood, and indicate that activity will exceed the seasonal average of 11 named storms, six hurricanes and two major hurricanes.

So the basic storm forecast looks similar from both centres.

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thanks for posting this :)

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Yeah the agencies do broadly agree on an above average season but probably not as hyperactive as 2010 in terms of numbers at least. A fairly safe call and I suspect something between 14-16NS is a solid call for now. I think the call of 13NS is a touch low from the Met office but then again I suspect the difference between that and the final figure will be hardly noticeable to thier prediction.

Of course just watch the ENSO go El nino or something daft like that now I've said this!

ps, I stand by this:

"Worth watching the next MJO wave as it rolls through the W.Caribbean in 2-3 weeks or so, that'll probably be the best shot at getting 'early'"

Interesting to see quite a few models trying to spin something up in the Caribbean, a little earlier then I thought but it would make sense given its a favoured area and also background conditions.

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We have invest 93L which formed east of Florida yesterday. The system was developing a LLC and had some persistant convection over it. However, 93L has now made landfall over Florida. The invest is racing southwestwards towards the Gulf Of Mexico, where it has a chance to become the season's first tropical depression if it can get it's act together quick enough before a second landfall on the gulf coast. Shear is currently low across the GOM, and waters are around 26-27C which could support tropical depression formation.

post-1820-0-71463900-1306961809_thumb.jp

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Thanks for the heads up. !

A couple of half chances here, if the track for 93L is further south into Mexico then it might have the time to develop, HWRF is a prime example of this taking it to a weak Tropical storm, the first of the season. However the prefered course seems to be further north with only 36 hrs or so of life left before landfall as its travelling pretty quickly.

Recently convection has flared away, but some good circulation is still there so just about time for something to develop, NHC have it at 10%.

There is another area of interest in the south Caribbean under a yellow alert also with 10%, this has a much broader area of convection with limited circulation, due to it's size and location though I don't really rate it's chances over the next couple of days. The biggest factor this one has it that the broad area of circulation is not due to move for nearly a week so it has plenty of time for the circulation to slowly develop over some pretty good SST's.

Further afield the ITCZ is slowly moving further north again with some active waves and good activity leaving Africa.

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