Loop Current Eddy cuts off; oil danger to Keys now greatly reduced

By: Dr. Jeff Masters , 2:24 PM GMT on May 28, 2010

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A major ocean current re-alignment is underway the Gulf of Mexico right now, and the new configuration that is developing greatly reduces the threat of oil entering the Loop Current and affecting the Florida Keys and U.S. East Coast. As I explain in my Loop Current Primer, the Loop Current is an ocean current that transports warm Caribbean water through the Yucatan Channel between Cuba and Mexico. The current flows northward into the Gulf of Mexico, then loops southeastward just south of the Florida Keys (where it is called the Florida Current), and past the western Bahamas. Here, the waters of the Loop Current flow northward along the U.S. coast and become the Gulf Stream. With current speeds of about 0.8 m/s, the Loop Current is one of the fastest currents in the Atlantic Ocean. Every 6 - 11 months, the top bulge of the Loop Current cuts off, forming a 250-mile diameter circular eddy in the middle of the Gulf of Mexico. This clockwise-spinning eddy is filled with warm water from the Loop Current, and is called a Loop Current Eddy. The main body of the Loop Current then takes a fairly direct eastward path from the Yucatan Channel to the Florida Keys.

Over the past two days, surface currents in the Gulf of Mexico have aligned to form a Loop Current Eddy, as seen in the analysis of surface currents done by the U.S. Navy (Figure 1, and see also a 30-day animation of the eddy forming.) It remains to be seen if the deep water currents have followed suit, and a stable Loop Current Eddy cannot exist until the deep water currents also cut off into a clockwise-rotating ring of water at depth. A NOAA Hurricane Hunter aircraft is out over the Gulf of Mexico today dropping expendable buoys and current probes to determine if a stable Loop Current Eddy has formed. Roffer's Ocean Fishing Forecast Service has a nice discussion on the Loop Current Eddy formation.


Figure 1. Comparison of surface currents in the Gulf of Mexico on May 19 (top) and May 27 (bottom) as simulated by the HYCOM model. On May 19, the Loop Current made a large northward loop into the Gulf, and was able to transport oil from the near the spill location southwards through the Keys. By May 27, this loop had cut off, and new oil moving southwards from the spill will now be trapped in the clockwise rotating Loop Current Eddy that is cut off from the Loop Current. Note on the west side of the Gulf of Mexico, off the coast of Texas, there is an old Loop Current Eddy that cut off from the Loop Current in July 2009. This eddy cut off in the same location as this week's eddy, and has drifted west-southwestward at 3 - 5 km per day over the past ten months. Image credit: U.S. Navy.

If the eddy does remain in place, it will greatly reduce the chances of oil making it to Cuba, the Florida Keys, and beyond. Any oil moving southwards from the spill location will now become entrained in the eddy, and will move in a 250 mile-wide clockwise circle in the east-central Gulf of Mexico. A small portion the oil will get shed away from the eddy's periphery and make it into the Loop Current and waters surrounding the eddy, but the concentrations of oil doing so will be small. Keep in mind, though, that during the first 1 - 2 months that a Loop Current Eddy forms, it is common for the eddy to exchange substantial amounts of water with the Loop Current, and in some cases get re-absorbed into the Loop Current. A 1-year animation of the Loop Current shows that the last Loop Current Eddy, which cut off in mid-July 2009, experienced a 2-week period in early August when it re-attached to the Loop Current. A significant portion of any oil entering the eddy during a period of re-attachment will be able to enter the Loop Current and flow past the Keys.

One bad result of the eddy breaking off is that now we have an extra source of heat energy for passing hurricanes during the upcoming hurricane season. Loop Current eddies have high-temperature water that extends to great depth, and hurricanes passing over such eddies often undergo rapid intensification. Hurricanes Katrina and Rita of 2005 both underwent rapid intensification as they passed over warm Loop Current eddies in 2005. The formation of a Loop Current Eddy during hurricane season means that a much greater portion of the Gulf of Mexico has deep, warm water capable of fueling rapid intensification of hurricanes.

Oil spill update
Light offshore northwesterly winds are expected to blow over the northern Gulf of Mexico today through Saturday, resulting decreased threats of oil to the Louisiana shore, according to the latest trajectory forecasts from NOAA. These offshore winds may be able to transport oil southwards into the Loop Current Eddy that just formed; a streamer of oil moving southeastward into the Loop Current Eddy is visible in yesterday's NASA MODIS imagery (Figure 2). Winds will shift to onshore out of the south on Saturday night, then shift to southwesterly by Tuesday. The long-range forecast from the GFS model indicates continued southwesterly winds all of next week. If this forecast verifies, we will see our greatest chances yet of significant amounts of oil reaching the beaches of Mississippi, Alabama, and the Florida Panhandle.


Figure 2. Visible satellite image of the Gulf of Mexico taken at 2:55pm EDT Thursday May 27, 2010, by the MODIS instrument on NASA's Aqua satellite. Thin streaks of oil can be seen moving southeast and then southwest around the eastern side of the new Loop Current Eddy. Image credit: NASA.

Oil spill resources
My post, What a hurricane would do the Deepwater Horizon oil spill
My post Wednesday with answers to some of the common questions I get about the spill
My post on the Southwest Florida "Forbidden Zone" where surface oil will rarely go
My post on what oil might do to a hurricane
NOAA trajectory forecasts
Deepwater Horizon Unified Command web site
Oil Spill Academic Task Force
University of South Florida Ocean Circulation Group oil spill forecasts
ROFFS Deepwater Horizon page
Surface current forecasts from NOAA's HYCOM model
Synthetic Aperture Radar (SAR) imagery from the University of Miami

Central American disturbance
The Atlantic is currently quiet, with none of our reliable global forecast models predicting tropical cyclone development over the next 6 days. There is an area of disturbed weather (90E) just off the Pacific coast of Mexico that will be a major concern for southern Mexico and much of Central America over the next 3 - 4 days. The disturbance will bring heavy rains to Central America during the weekend, potentially bringing serious flooding rains to portions of Mexico, Guatemala, El Salvador, Honduras, and Nicaragua. NHC is giving the disturbance a high (>60% chance) of the disturbance developing into a tropical depression by Sunday. Wunderbloggers Weather456 and StormW have more on the tropics.


Figure 3. Satellite image of the Central American disturbance 90E this morning.

Join the "Hurricane Haven" with Dr. Jeff Masters: a new Internet radio show
Beginning next week, I'll be experimenting with a live 1-hour Internet radio show called "Hurricane Haven." The show will be aired at 4pm EDT on Tuesdays, with the first show June 1. Listeners will be able to call in and ask questions. Some topics I'll cover on the first show:

1) What's going on in the tropics right now
2) Preview of the coming hurricane season
3) How a hurricane might affect the oil spill
4) How the oil spill might affect a hurricane
5) New advancements in hurricane science presented at this month's AMS Conference on Hurricanes and Tropical Meteorology
6) Haiti's vulnerability to a hurricane this season

I hope you can tune in to the broadcast, which will be at http://www.wunderground.com/wxradio/wubroadcast.h tml. If not, the show will be recorded and stored as a podcast.

I'll be back with at least one update over the coming 3-day Memorial Day weekend. Have a great holiday!

Jeff Masters

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Quoting Patrap:


Yeah,,we were ,are in the Middle of a lotta outflows,,bone dry still Here At Mag & Jeff

Still dry in Covington...(pool in Mandeville)
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2656. Michfan
Quoting AllStar17:
5 pm Advisory:


Hey allstar where do you get that KMZ file for that image?
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2655. Patrap
Nasty storms atmo..., Im bone dry still.That One South down near Lafitte was Booming.

Member Since: July 3, 2005 Posts: 424 Comments: 128279
Hail report at Belle Chasse, too:

1944 100 BELLE CHASSE PLAQUEMINES LA 2985 9000 (LIX)
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That's a very wet & stormy sat afternoon.. it has been a while! That moiture tongue over the N/ NE caribbean islands is bringing us some much needed rain.
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Quoting Patrap:
Speaking of Outflows..

A Nwest bound mini Cold front is stirring trouble


Yeah, washed out the day at the pool, up here...

And little warning before the first boom...was fairly close. Though, those of us paying attention could easily tell you that particular cloud mass was capable of lightning.
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2650. KEEPEROFTHEGATE (Mod)
01E/TS/A
MARK
14.1N/91.9W
MOVEMENT NEN
Member Since: July 15, 2006 Posts: 171 Comments: 53835
2649. xcool
kmanislander haha
Member Since: September 26, 2009 Posts: 2 Comments: 15670
Well, it feels like summer here which means BBQ time !!. In preparation for my cherry wood smoked baby backs I must now hit the gym.

Catch you all later.
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2647. xcool



Member Since: September 26, 2009 Posts: 2 Comments: 15670
2646. Levi32
Quoting Drakoen:
Their position doesn't explain why that airport reported winds switching from east to northeast to north as if a storm was making landfall...


I dunno....the position of that weather station isn't exactly clearly on the western side of the apparent COC on satellite imagery. It almost looks like winds should be either calm under the center or southerly if anything.
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Quoting Drakoen:


It happened over a pretty good span

Link


I see. Very odd because that is the signature of a landfalling system. That wind kept pulling around.
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Quoting shakaka:


Even funnier are those on here who basically word for word repeat after Levi/456/Drak like 10 minutes after theirs and answering the same exact question. Kills me every time. Lots of deja vu in this blog!
I thought I was the only one who noticed that. LOL
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2643. shakaka
Quoting SouthALWX:

Not that I disagree or to be insulting but ...
is Joe Bastardi, by chance, your favorite forecaster ... lol some things you say seem to be exactly what Joe B said the day before, but rephrased .... maybe you just think alike ;)


Even funnier are those on here who basically word for word repeat after Levi/456/Drak like 10 minutes after theirs and answering the same exact question. Kills me every time. Lots of deja vu in this blog!
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2642. Patrap
Quoting KC2NOLA:
Definitely strange weather here Pat. Drove from Tchoupitoulas to Claiborne via Nashville and the clouds, wind and rain changed drastically over a 10 block route.


Yeah,,we were ,are in the Middle of a lotta outflows,,bone dry still Here At Mag & Jeff
Member Since: July 3, 2005 Posts: 424 Comments: 128279
2641. Drakoen
Quoting kmanislander:


Perhaps a localised downburst ?


It happened over a pretty good span

Link
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Quoting Levi32:


I don't know why the NHC said she still may strengthen...to me it looks like the deterioration process has already begun.


I just ran the IR loop again and the cloud tops are warming very rapidly. Save for the one convective blow up just West of the Guatemalan border the deep convection has waned.

It will be interesting to see how much rain the mountains wring out of this once it starts pushing up those slopes in earnest
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2639. xcool
haha 40 c haha
Member Since: September 26, 2009 Posts: 2 Comments: 15670
2638. KC2NOLA
Definitely strange weather here Pat. Drove from Tchoupitoulas to Claiborne via Nashville and the clouds, wind and rain changed drastically over a 10 block route.
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ALTHOUGH VISIBLE AND INFRARED SATELLITE IMAGERY INDICATE SOME
EROSION OF THE CENTRAL CONVECTION...MICROWAVE IMAGERY INDICATES THAT
BANDING FEATURES HAVE CONTINUED TO IMPROVE EAST AND SOUTH OF THE
CENTER. THE INITIAL INTENSITY IS INCREASED TO 40 KT BASED ON A
SATELLITE INTENSITY ESTIMATE OF 35 KT FROM BOTH TAFB AND SAB AND
THE TIGHTER BANDING FEATURES NOTED IN MICROWAVE IMAGERY.

THE INITIAL MOTION ESTIMATE IS 055/06 KT...WHICH MAY BE A LITTLE
SLOW. AGATHA IS EXPECTED TO CONTINUE MOVING IN A NORTHEASTWARD OR
EAST-NORTHEASTWARD DIRECTION FOR THE NEXT 24 HOURS AS THE CYCLONE
MOVES AROUND THE WEST SIDE OF A BROAD MID-LEVEL RIDGE THAT LIES
ALONG 12N LATITUDE. LANDFALL IS EXPECTED TO OCCUR ALONG THE
GUATEMALAN COAST BY SUNDAY MORNING.
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2636. IKE
Quoting Patrap:
Seems my living room will be cool,and the Kitchen Normal here Ike..

LOL


LOL...

I needed the rain here. Glad to get it...cooled off to 68 degrees.
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2635. Patrap
Seems my living room will be cool,and the Kitchen Normal here Ike..

LOL
Member Since: July 3, 2005 Posts: 424 Comments: 128279
Quoting Patrap:
Speaking of Outflows..

A Nwest bound mini Cold front is stirring trouble


thats like the one that was northbound here. if it smacks into westward moving waves from outflow, heads up! gusty as hell (and the trees are confused Im sure)
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2633. Levi32
Quoting kmanislander:


Being a stone's throw from land and with friction already eroding the Northern semi circle of the storm there is little chance of further intensification IMO


I don't know why the NHC said she still may strengthen...to me it looks like the deterioration process has already begun.
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2632. IKE
6-10 day temperatures...

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2631. Patrap


Agatha Model Plots
Member Since: July 3, 2005 Posts: 424 Comments: 128279
2630. Levi32
Quoting Drakoen:


That's true but I hope you will be able to expand your horizon...


Oh I won't have a choice if I ever get to a Meteorology school lol.
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re:2612 I got caught in one yesterday at Mcdonalds in Tillmans Corner. Thought I was gonna have to throw my wife out the car as a sacrificial lamb.....LOL
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Quoting Drakoen:
Their position doesn't explain why that airport reported winds switching from east to northeast to north as if a storm was making landfall...


Perhaps a localised downburst ?
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Quoting kmanislander:


Being a stone's throw from land and with friction already eroding the Northern semi circle of the storm there is little chance of further intensification IMO
Yeah, I don't see anymore intensification taking place, but you never know.
Member Since: September 2, 2009 Posts: 130 Comments: 21193
2625. Patrap
Speaking of Outflows..

A Nwest bound mini Cold front is stirring trouble

Member Since: July 3, 2005 Posts: 424 Comments: 128279
hey guys you know what I realise that from the begining of the TS til now the forecast track has moved more east every time and dissapation time more east as well
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2623. Levi32
Quoting SouthALWX:

knew you sounded familiar ... ;) Keep at it. I dont subscribe so it works for me. I noticed you have disagreed a few times with him, so you're not incompetent alone, either.


Thanks for noticing that. I make it a point not to be led around by man or model, but learn what I can from both and formulate my own conclusions.
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Quoting AllStar17:
5 pm Advisory:


Where can I find this site? Can you put a link here, please?
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Quoting Patrap:


This ULL is a Whoppa,..it has a tropical feel tropical here..and August Like
"
you aint kiddin. good news is that it is a cold rain. feels great in the heat. I assume the incredible temp contrast from the outflow triggered the west moving wave.
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2620. Patrap
Quoting Drakoen:
Their position doesn't explain why that airport reported winds switching from east to northeast to north as if a storm was making landfall...


Maybe that convective burst was rotating within that Semi circle of the Overall..

Dunno
Member Since: July 3, 2005 Posts: 424 Comments: 128279


According with this image very near to coast but the center not sure is onshore.
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Quoting MiamiHurricanes09:
If it intensifies a little more, chances of it going into the Caribbean increase. Steering in the 999-990 MSLP layer seems a little more favoring the Caribbean.


Being a stone's throw from land and with friction already eroding the Northern semi circle of the storm there is little chance of further intensification IMO
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2617. Drakoen
Their position doesn't explain why that airport reported winds switching from east to northeast to north as if a storm was making landfall...
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2616. Patrap
Quoting SouthALWX:
Okay, WEIRD. I was just at the intersection of a breeze front and a gravity wave! crazy weather! gusts to 50 MPH out of two different directions! (east then SW as the wave crests passed!) some of the strangest weather Ive seen ever! check it out on mobile radar!


This ULL is a Whoppa,..it has a tropical feel tropical here..and August Like
Member Since: July 3, 2005 Posts: 424 Comments: 128279
Quoting wunderkidcayman:
new map
1010-1000range


and
999-990 range

If it intensifies a little more, chances of it going into the Caribbean increase. Steering in the 999-990 MSLP layer seems a little more favoring the Caribbean.
Member Since: September 2, 2009 Posts: 130 Comments: 21193
Quoting PcolaDan:
On possibly a positive note, a faster moving Agatha may mean less rain for the region.
The volcano Pacaya which erupted earlier this week is close to some of Guatemala's most prized coffee plantations. The national coffee association, Anacafe, had no immediate reports of serious damage to crops.

Coffee workers said on Friday rain from the storm was helping to clean ash off trees and were optimistic crop damage would be minimal.

Agatha's increased forward speed will help the folks in Guatemala and C America avoid terrible flooding.
Member Since: August 25, 2009 Posts: 20 Comments: 6785
2613. Patrap
Quoting kmanislander:


If the center is where they say it is it won't take until Sunday morning to come ashore.


Sure wont Kman,,dont know how they work a slide rule sumtimes.
Member Since: July 3, 2005 Posts: 424 Comments: 128279
Okay, WEIRD. I was just at the intersection of a breeze front and a gravity wave! crazy weather! gusts to 50 MPH out of two different directions! (east then SW as the wave crests passed!) some of the strangest weather Ive seen ever! check it out on mobile radar!
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I see it clearly now with my new glasses
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Quoting Patrap:
That big convective Burst is inland and where the deed is being done,bu the center is still Se of that


If the center is where they say it is it won't take until Sunday morning to come ashore.
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Quoting Patrap:
That big convective Burst is inland and where the deed is being done,bu the center is still Se of that


exactly
Member Since: March 10, 2010 Posts: 1 Comments: 7688
2608. cg2916
Quoting xcool:
MiamiHurricanes09 100% free


Where do you get it?
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About

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