Still watching for a potential early-season Atlantic subtropical storm

By: Dr. Jeff Masters , 7:10 PM GMT on May 16, 2009

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The latest 00Z and 12Z runs of the GFS, UKMET, NOGAPS, and ECMWF global dynamical computer models continue to indicate the possibility of an early season subtropical storm forming in the Gulf of Mexico 3 - 7 days from now. A modest area of low shear air is expected to open up between the polar jet stream to the north and the subtropical jet stream to the south, between Cuba and the northern Gulf of Mexico. The models have not been consistent with the timing or the size of this low shear area, and I wouldn't be surprised to see them back off again from this forecast with Sunday's set of runs. Nevertheless, I'll call once again for a 10% chance of development of a subtropical depression in the eastern Gulf of Mexico, 4 - 7 days from now. There isn't much of a disturbance at present to look at--there are some scattered showers between Cuba and Jamaica, but they are under a hefty 30 knots of wind shear. These showers should gradually increase in intensity and areal coverage over the next two days, and phase space diagrams from Florida State University indicate that an extratropical low may form near the western tip of Cuba 2 - 3 days from now. The storm may then gradually transition to a subtropical or tropical system later in the week, if the shear is low enough. Even if the shear is high and the storm remains extratropical, it could be a substantial rain-maker where it comes ashore. The models target the northern Gulf Coast between Louisiana and the Florida Panhandle as the most likely landfall location, but it is too early to place any confidence in this track.

There is also about a 10% chance a subtropical storm may form in the mid-Atlantic a few hundred miles east of Bermuda. There, a large upper-level cold low has cut off from the jet stream, and it may spin in place long enough over the next week to develop a warm core and be classified as a subtropical storm. It is unlikely that a subtropical storm forming that far out in the Atlantic this early in the year would pose a threat to any land areas, with the possible exception of Bermuda.

Climatology of early-season Atlantic tropical cyclones
Tropical storms are uncommon in the Atlantic before June 1, with only 26 named storms on record between 1851 - 2008. Five of these have made it to hurricane strength, and only one--Hurricane Able of 1951--made it to major hurricane status. Last year's Tropical Storm Arthur may be the deadliest May tropical cyclone on record. Though only a 40 mph tropical storm at landfall, Arthur killed five people in Belize and caused $78 million in damage. Three early-season storms have brought hurricane-force winds to land. The March 1908 hurricane swept through the northern Lesser Antilles Islands as a Category 1 or 2 hurricane, destroying at least 24 boats and causing damage to buildings on St. Bartholomew. Hurricane Able of 1951 brought sustained winds of 90 - 95 mph to the northern Bahama Islands, but caused little damage. Hurricane 2 of May 1908 hit North Carolina's Outer Banks as a Category 1 hurricane, but also caused little damage.


Figure 1. Tracking map for the earliest hurricane to make landfall, the March 1908 hurricane in the northern Lesser Antilles Islands.

List of all early season (formed in January - May) Atlantic named storms
May 31, 2008: Tropical Storm Arthur
May 6, 2007: Subtropical Storm Andrea
April 18, 2003: Tropical Storm Ana
April 21, 1992: Subtropical Storm 1
May 6, 1981: Tropical Storm Arlene
January 18, 1978: Subtropical Storm 1
May 21, 1976: Subtropical Storm 1
May 23, 1972: Subtropical Storm Alpha
May 17, 1970: Hurricane Alma (Category 1)
May 28, 1959: Tropical Storm Arlene
February 2, 1953: Tropical Storm Alice
May 25, 1952: Tropical Storm 1
May 15, 1951: Hurricane Able (Category 3)
May 22, 1948: Tropical Storm 1
May 19, 1940: Tropical Storm 1
May 27, 1934: Tropical Storm 1
May 14, 1933: Tropical Storm 1
May 5, 1932: Tropical Storm 1
May 13, 1916: Tropical Storm 1
May 24, 1908: Hurricane 2 (Category 1)
March 6, 1908: Hurricane 1 (Category 2)
May 27, 1890: Tropical Storm 1
May 16, 1889: Hurricane 1 (Category 1)
May 17, 1887: Tropical Storm 2
May 15, 1887: Tropical Storm 1
May 30, 1865: Tropical Storm 1

I'll have an update Sunday.

Jeff Masters

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Quoting SevereHurricane:


I speak it and type it. :D


I guess that makes 2 of us.
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Alright.. so what did I miss.. other the the standard who might be who and wishcaster BS... any weather news?
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g'nite bloggers i'll be back in the very early a.m to check up on things
god bless be well guys
I'd still watch the system east of Bermuda. Looks to be a bit more convective activity near the center than earlier today.
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Quoting HurricaneKing:
What happened to the english language?


I speak it and type it. :D
Member Since: September 7, 2008 Posts: 17 Comments: 1604
Blog Refresh
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just playin taz
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Quoting WeatherStudent:
guys whats the pressure criteria for a td the pressure would have to be what and below


No real requirement...average I see is about 1009. I've seen em in a range of about 1006-1014.
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Quoting KEEPEROFTHEGATE:
and always listen to state and local officials


LOL...
Member Since: September 7, 2008 Posts: 17 Comments: 1604
Hey Taz!
you forgot westcaster
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and always listen to state and local officials
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What happened to the english language?


The 00z (Midnight run) and 12z (afternoon run) of the computer models are normally the best. They have the most data from more sources incorporated into them.
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Quoting WeatherStudent:
guys whats the pressure criteria for a td the pressure would have to be what and below


you just have to have a closed low pressure

this will NOT be a td before tomorrow night
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guys whats the pressure criteria for a td the pressure would have to be what and below
Quoting KEEPEROFTHEGATE:
and baby food and diapers


And make sure you pay close attention to you local news.
Member Since: September 7, 2008 Posts: 17 Comments: 1604
pl if y'all say so whtever you guys are the experts not moi
and baby food and diapers
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Quoting KEEPEROFTHEGATE:
ya you might want to get yer flashlight and batteries ready
lol


Don't forget the Plywood, candles, and Poptarts.
Member Since: September 7, 2008 Posts: 17 Comments: 1604
Lets see if a low forms soon that the models can initiate their first positions,instead of having different positions to start.
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Quoting WeatherStudent:
besides the midnight gfs run is alwats the weaker run of all three, so tahs self explanotry would you think bud?


First off,
The run isn't close to being done,
Second,
Its looking better on satellite by the frame.
Third,
It looks rather similar to the 18z run.
ok buddy?
Member Since: September 7, 2008 Posts: 17 Comments: 1604
Quoting presslord:
Drak...I'm thinkin' you'e rigt....


U r3Alli 7hiNk 5o???
Member Since: October 28, 2006 Posts: 57 Comments: 30613
Quoting WeatherStudent:
we'll probably wake up to morning to a swriling puff of clouds
ya you might want to get yer flashlight and batteries ready
lol
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Quoting Drakoen:
who is frak?



sorry for mispronuncing your name
Drak...I'm thinkin' you'e rigt....
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Quoting WeatherStudent:


so d i


wow... didnt you just say the 00z run is the weakest?
just wow...
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who is frak?
Member Since: October 28, 2006 Posts: 57 Comments: 30613
GFS hasn't changed much from its previous run. Perhaps a more weaker system approaching the Panhandle
Member Since: October 28, 2006 Posts: 57 Comments: 30613
nice to see you as well, thouhts on phenomanlly encouring gfs run on our system tonight frak?
Quoting hurricanealley:
I have a feeling the next gfs model run will drop it.
doesnt matter any more there is actually something there and iam looking right at it it needs to persist for another 8 hr and it will be 24
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we'll probably wake up to morning to a swriling puff of clouds
WeatherStudent-PresidentialElection-JFV
Member Since: October 28, 2006 Posts: 57 Comments: 30613
Quoting hurricanealley:
I have a feeling the next gfs model run will drop it.


so d i
Quoting WeatherStudent:
besides the midnight gfs run is alwats the weaker run of all three, so tahs self explanotry would you think bud?


why is it the weakest one... it looks the best it has ever looked right now...
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I have a feeling the next gfs model run will drop it.
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besides the midnight gfs run is alwats the weaker run of all three, so tahs self explanotry would you think bud?
Quoting WeatherStudent:


yes a dud adrian thank god


Always been a dud iam not really expecting much out of this but some soaking rain for florida.
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yeah and thats weak...
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now adrian thats still a hefty td enough to bring winds of 40 mph and at least a ts watch to your counties wouldn't you think so?
Quoting hurricane23:
weak low over southern florida on the 00z GFS.


yes a dud adrian thank god
Quoting cchsweatherman:


Having a hard time comprehending the solution proposed by this latest NAM model. Seems like a total mess if you ask me. But then again, the NAM has always been the worst with tropical cyclogenesis.


It believes the front will get to the storm more than earlier thought. It will be almost like the cut off over the atlantic was in the beginning multiple vorticies competing for control.

Speaking of the cut off it's looking pretty good right now. Thanks to the dry air between the bands and the convection trying to build it actually has an pseudo eye feature.
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weak low over southern florida on the 00z GFS.
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789. beell
Quoting atmoaggie:


Why they include NAM in that suite is beyond me...


Well, the NAM is sure not known for being a tropical model but with any system this close in, upstream weather will ultimately play a large part in track. In the case of this potential system-upstream weather may also play a part in intensity.

Upstream is NAmerica. I like looking at it anyway-variety at least!
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Interesting..Deep convection is increasing.

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heres a close up still image of cell between cuba and n jamaica at 19n/77w
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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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