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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Regardless of if it becomes anything...it will bring us here in Florida...lots of rain...which we need badly!
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Remind me of Barry actually.
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Quoting IKE:
6Z GFS
Looks like the system wants to follow Fay's footsteps per this model run.

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Good morning all

To get a good look at where the actual rotation is with the trough see the shortwave loop. Just off to the W and WSW of the Western end of Jamaica.

Shear has pushed the convection about 50 to 100 miles East of the axis.

Link
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983. IKE
Here's a nice satellite loop of the system...Link

All of that moisture that's east of it should eventually get drawn into south Florida.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
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I keep on waiting for the TWO for the Atlantic..
then I remember its May 17th.
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Quoting IKE:
Look south of Miami....between south Florida and the northern coast of Cuba and the curve to the clouds.....


Dang... that thing's gotten way more organized.
Member Since: December 21, 2007 Posts: 13 Comments: 3044
Tropical Update

Don't watch the convection when trying to locate a center, the system is being sheared, thus the center and convection are two different places.
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Morning all, I see our blob did really well during DMAX.
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977. IKE
From the 8:05 am EDST TWD...

THE CARIBBEAN SEA...
A MIDDLE LEVEL TO UPPER LEVEL TROUGH EXTENDS FROM THE STRAITS OF
FLORIDA...ACROSS CUBA AND JAMAICA...INTO THE SOUTHWESTERN CORNER
OF THE AREA. THIS TROUGH HAS PERSISTED IN MORE OR LESS THE SAME
AREA FOR AT LEAST THE LAST 72 HOURS OR SO. A SURFACE TROUGH HAS
BECOME MORE PRONOUNCED IN SHORTWAVE INFRARED SATELLITE IMAGERY
ALONG 79W/80W FROM 16N TO 21N.
MOIST UPPER LEVEL SOUTHWESTERLY
WIND FLOW IS ON THE EASTERN SIDE OF THE TROUGH ACROSS THE
REMAINDER OF THE CARIBBEAN SEA TO THE EAST OF 70W. THE CYCLONIC
FLOW AROUND THE TROUGH COVERS THE AREA ROUGHLY TO THE EAST OF
THE LINE FROM GUADELOUPE TO THE GUAJIRA PENINSULA OF
NORTHEASTERN COLOMBIA. SCATTERED MODERATE SHOWERS TO ISOLATED
STRONG THUNDERSTORMS ARE FROM 16N TO 20N BETWEEN THE JAMAICA
CHANNEL AND 78W.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting IKE:
Take care surfmom.


: ) you TOO!! I like IKE!!!!
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Quoting IKE:


I would imagine so.

It's been so dry down there, I think I would wait til after this moves through to burn.


Oh yes.... I'm not even lighting a B-day candle outside... place out east is combustible.....just if it's nasty I have to worry about the stuff branches going air borne etc.
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974. IKE
Take care surfmom.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting aquak9:
post 955

don't freak, ya'll...it's not the real stormtop, notice the zero instead of the letter "O"


didn't freak -- good thing you can see so well in the AM
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Ohhh I see it, look at that nuget -- I hope all I see is rain and NOT trouble...... shhhh I do spy some wave potential too!

Got yard work and then a paddle in the gulf.....won't be flat forever.
SURF
Another flat weekend on tap for the GC, with afternoon thunderstorms forecasted everyday. Fishing red hot right now on the beach with Tarpon schooling close to shore. Have a great weekend.
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971. IKE
Quoting surfmom:
hummmm coffee and weather maps -- I love it -- used to be a newspaper... gave that up......tired of the humans thinking their in charge.......
So we have a DROUGHT BUSTER here, Ike -- love the line... might borrow it! Wasn't completely ready for this...... work wise - Got a huge pule of debris that was to be burned off --cept w/the drought we couldn't..... do you think we're going to have some wind with this...over 20mph???


I would imagine so.

It's been so dry down there, I think I would wait til after this moves through to burn.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
post 955

don't freak, ya'll...it's not the real stormtop, notice the zero instead of the letter "O"
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hummmm coffee and weather maps -- I love it -- used to be a newspaper... gave that up......tired of the humans thinking their in charge.......
So we have a DROUGHT BUSTER here, Ike -- love the line... might borrow it! Wasn't completely ready for this...... work wise - Got a huge pule of debris that was to be burned off --cept w/the drought we couldn't..... do you think we're going to have some wind with this...over 20mph???
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Gitmo Radar- Link
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967. IKE
Quoting surfmom:
Ike -- up so early on a sunday morning???? must be something to look at.... hee, hee


Yeah...fixing to finish mowing my yard in about an hour.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
966. IKE
Look south of Miami....between south Florida and the northern coast of Cuba and the curve to the clouds.....

Member Since: June 9, 2005 Posts: 23 Comments: 37858
Ike -- up so early on a sunday morning???? must be something to look at.... hee, hee
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Quoting IKE:


Wind shear is 30 knots...should drop by tomorrow. The 20 knot and lower shear line is dropping south toward the circulation.


For some reason, I want something to form, but for it to be helpful to the FL drought (I'm in SC, though).
Member Since: December 21, 2007 Posts: 13 Comments: 3044
963. IKE
Quoting cg2916:

The consensus. ANd wind shear should be very low so I don't know what's keeping this system from forming.


Wind shear is 30 knots...should drop by tomorrow. The 20 knot and lower shear line is dropping south toward the circulation.

Member Since: June 9, 2005 Posts: 23 Comments: 37858
Cuba system AVN.
Member Since: December 21, 2007 Posts: 13 Comments: 3044
Wind shear tendency- Link

Actual Wind Shear- Link
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Quoting IKE:


What model do you see backing off?

Not sure it will ever be tropical. I'll go with STS as my final call.

Really doesn't matter....winds and rain for most of Florida. Drought-buster for the peninsula.

The consensus. ANd wind shear should be very low so I don't know what's keeping this system from forming.
Member Since: December 21, 2007 Posts: 13 Comments: 3044
959. ackee
its been raining non stop here in kington since last night is there a low forming near jamaica?
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I can tell you one thing, the system near Cuba is way more organized than when this post was made.
Member Since: December 21, 2007 Posts: 13 Comments: 3044
957. IKE
Quoting cg2916:

It looks like the models are backing off with it. And when is this thing going to get a low with it?


What model do you see backing off?

Not sure it will ever be tropical. I'll go with STS as my final call.

Really doesn't matter....winds and rain for most of Florida. Drought-buster for the peninsula.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Looks like if it keeps scooting east, Haiti will tear it apart- Link
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Quoting Weather456:
GFS now intialize something as early as 2mr


It looks like the models are backing off with it. And when is this thing going to get a low with it?
Member Since: December 21, 2007 Posts: 13 Comments: 3044
GFS now intialize something as early as 2mr

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Quoting Weather456:


hello, long time no see.


Looks like he fixed his caps lock button!
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Quoting STORMT0P:
interesting....


hello, long time no see.
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950. IKE
Gale conditions expected within 240 nm NW quadrant of low late Tue through Wed.....

out in the GOM, east of 90W.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting IKE:
6Z GFS


Brings it a little closer to the other models.
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947. IKE
6Z GFS
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946. IKE
6Z NOGAPS
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945. IKE
MARINE WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
445 AM EDT SUN MAY 17 2009


ATLC AND GULF OF MEXICO...
FORECAST DEVELOPS A SURFACE LOW S OF CUBA TUE AND LIFTS IT
SLOWLY NORTH TOWARD THE FL KEYS THROUGH TUE NIGHT AND THEN TURNS
THE SYSTEM MORE NW INTO THE GULF OF MEXICO. AS PER COORDINATION
WITH HPC AND MFL...SLOWED DOWN THE NORTHERLY PROGRESS OF THE 00Z
GFS. THE FORECAST RELIES ON A 00Z GFS/ECMWF BLEND. CONFIDENCE IN
THE GFS DECREASES SIGNIFICANTLY TUE ONWARD AS THE 00Z CONTINUES
TO OVER-AMPLIFY THE VORTICITY ON THE EASTERN SIDE OF THE MID
LEVEL LOW...DRAGGING THE LOW TRACK EASTWARD. HOWEVER...THERE IS
SOME CONCERN THAT THE GFS MAY BE RIGHT FOR THE WRONG REASONS AS
THE 00Z UKMET HAS TRENDED MORE EASTERLY WITH THE LOW TRACK AFTER
THE LOW INCORPORATES THE MID LEVEL VORTICITY FROM THE DEEP LAYER
TROUGH EXPECTED TO PASS NORTH OF THE SYSTEM MON. FOR NOW...WILL
SLOWLY TREND TOWARD A MORE EASTERLY TRACK INTO THE GULF OF
MEXICO TUE-THU...WITH THE STRONGEST WINDS IN THE SW N ATLC N OF
THE BAHAMAS ON THE NORTHERN SIDE OF THE WARM FRONT AND IN THE
GULF IN THE NW QUADRANT OF THE LOW WED AND EXPANDING TO N
SEMICIRCLE THU. MODELS AGREE ON MOVING THE LOW NW INTO THE
CENTRAL GULF BY THE END OF THE PERIOD AS THE RIDGE TO ITS N
PASSES E FROM THE TN VALLEY WED AND OFF THE MID ATLC COAST THU.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Good morning to all.

72 hour TAFB forecast

img
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943. IKE
NO,LA long-term...

"LONG TERM...
COULD BE AN INTERESTING END OF THE WEEK AND WEEKEND. GFS AND ECMWF
ARE COMING INTO AGREEMENT ON A SOLUTION WITH THE UPPER LOW
EXPECTED TO FORM OVER THE SOUTHEAST GULF OF MEXICO. GENERAL TRACK
WOULD BE FROM NEAR TAMPA AREA ON WEDNESDAY TO THE MOBILE-PENSACOLA
AREA FRIDAY...THEN OVER CENTRAL MISSISSIPPI AND ALABAMA FOR THE
WEEKEND. ECMWF IS SLIGHTLY SLOWER AND STRONGER...BUT SAME GENERAL
TRACK. THIS TRACK WOULD HAVE OUR AREA ON THE `DRIER` SIDE OF THE
LOW TRACK.

WE WILL BEGIN TO SEE CLOUDS INCREASE WEDNESDAY WITH CHANCES FOR
PRECIPITATION RETURNING THURSDAY. FOR NOW...WILL KEEP 12 HOUR POPS
IN THE CHANCE RANGE FOR THURSDAY AND BEYOND UNTIL TIMING AND STRENGTH
IS A LITTLE BETTER DEFINED. MAIN CONCERNS WILL BE POTENTIAL FOR
VERY HEAVY RAIN...ESPECIALLY AROUND FRIDAY AND SATURDAY.

WILL GO GENERALLY CLOSE TO THE MEX GUIDANCE FOR THE EXTENDED PERIOD.
GFS SOLUTION IS DRIVING THE FORECAST FOR THE END OF THE WEEK."
Member Since: June 9, 2005 Posts: 23 Comments: 37858
942. IKE
Quoting RTLSNK:
Morning early birds,

67*F in Macon, Ga this morning, 98% humidity

Nice half inch of rain last night, more on the way

Anyone else having trouble with the Nexrad radar? Regional radar won't do a loop anymore.


I'm not having any problems.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
941. IKE
Mobile,AL long-term...

"LONG TERM...(TUESDAY NIGHT THROUGH SUNDAY)GUIDANCE AGREES WITH THE
SYSTEM OVER THE GULF MEANDERING NORTHWARD. THE ECMWF`S SOLUTION OF
THE SURFACE LOW MOVING OVER THE FA 24-36HRS SLOWER THEN THE GFS
CONTINUES. BOTH ARE FASTER THAN YESTERDAY`S 00Z GUIDANCE...WITH HE
GFS ADVERTISING THE SURFACE LOW MOVING OVER THE NW FL PANHANDLE GULF
COAST THURSDAY NIGHT...THE ECMWF NOW SATURDAY MORN. THE ENSEMBLE MEAN
CONTINUES TO STICK WITH THE OP GFS SOLUTION...ALTHOUGH A BIT
SLOWER...SO HAVE WENT THAT DIRECTION.

HAVE LITTLE CONCERN WITH THIS SYSTEM BECOMING THE FIRST TROPICAL
STORM OF THE YEAR AS FEEL THERE IS ENOUGH UPPER LEVEL SHEAR TO LIMIT
THIS."

Member Since: June 9, 2005 Posts: 23 Comments: 37858
Morning early birds,

67*F in Macon, Ga this morning, 98% humidity

Nice half inch of rain last night, more on the way

Anyone else having trouble with the Nexrad radar? Regional radar won't do a loop anymore.
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939. IKE
COC appears near western Cuba. Convection is to the east due to shear.
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938. IKE
You can kind of see what's going to happen looking at shear maps and satellite. I notice pressures have fallen about 1/2 to 1 mb over the last 24 hours in the eastern GOM and points south.

Looks like an STS is likely.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
937. IKE
Morning everybody...

Ah...first sip of freshly brewed coffee...

6Z NAM looks close to that 00Z ECMWF.
Member Since: June 9, 2005 Posts: 23 Comments: 37858

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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.