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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AOI

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Humour in Comments
Member Since: Posts: Comments:
1556. xcool
got love gfs
Member Since: September 26, 2009 Posts: 2 Comments: 15626
Quoting Hurricanes101:
GFS long range is very plausible

could have Alex in the BOC in about 2 weeks


Audrey! Oh Alex lol
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1554. xcool
i'm not leave
Member Since: September 26, 2009 Posts: 2 Comments: 15626
1553. EricSFL
Quoting xcool:
wow people leave


Yeah,I think they don't like "chongas"...
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Quoting xcool:
:0
Theres not many left on here.
Member Since: Posts: Comments:
Quoting Hurricanes101:
GFS long range is very plausible

could have Alex in the BOC in about 2 weeks


Yeah. I saw that. That's probably the 4 or 5th run showing that. Will watch and wait of course.
No more like this one please.

Member Since: Posts: Comments:
1550. xcool
wow people leave
Member Since: September 26, 2009 Posts: 2 Comments: 15626
Quoting Weather456:
I'm gonna call it a night.

Good night all.
Good night see you tomorrow.
Member Since: Posts: Comments:
1548. xcool
:0
Member Since: September 26, 2009 Posts: 2 Comments: 15626
1547. KEEPEROFTHEGATE (Mod)
iam gone as well later all see what first light may bring
Member Since: July 15, 2006 Posts: 169 Comments: 53296
I'm gonna call it a night.

Good night all.
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Quoting alexhurricane1991:
True but it is in the long range and it will change many times.


yup it sure can
Member Since: Posts: Comments:
Quoting Hurricanes101:
GFS long range is very plausible

could have Alex in the BOC in about 2 weeks
True but it is in the long range and it will change many times.
Member Since: Posts: Comments:
Quoting Hurricanes101:
GFS long range is very plausible

could have Alex in the BOC in about 2 weeks


Plausible...but not reliable.

I kinda learned over the years to ignore models out past 168 hrs unless doing a seasonal outlook.

But as you said, you can pick up a pattern or two in the long range forecasts.
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Its plausible because it is in an area that normally sees development in Early June
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1540. Grothar
Quoting FIU2010:
They're called las chunags de miami, lol


Is that with an i or a u?
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1539. KEEPEROFTHEGATE (Mod)
Quoting FIU2010:
morning, keeps, groovy looking avatar, lol
its a new 2010 look i call him oil slick man
Member Since: July 15, 2006 Posts: 169 Comments: 53296
1538. EricSFL
Quoting Hurricanes101:
GFS long range is very plausible

could have Alex in the BOC in about 2 weeks


You shouldn't trust the GFS that far out.
Member Since: Posts: Comments:
GFS long range is very plausible

could have Alex in the BOC in about 2 weeks
Member Since: Posts: Comments:
Quoting Weather456:


correct. Remnant energy carrying moisture to the GOM.
Alright sounds good i wouldnt mind some rain here in odessa north of tampa.
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Simple as 1, 2, 3


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1534. xcool
Grothar lol hi
Member Since: September 26, 2009 Posts: 2 Comments: 15626
Quoting alexhurricane1991:
Okay thanks again so what the gfs is saying what we are saying.


correct. Remnant energy carrying moisture to the GOM.
Member Since: Posts: Comments:
1532. Drakoen
I have 90E at 13.1N 94W
Member Since: October 28, 2006 Posts: 57 Comments: 29928
Quoting Weather456:


Keep in mind that weak, sheared disturbance in post 1506 does not imply a tropical system. The remnant moisture you pointed to is more or a less a disturbance.
Okay thanks again so what the gfs is saying what we are saying.
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1530. Grothar
Quoting xcool:
TampaSpin hey friend...


Yo xcool! Still posting those graphs, I see. Sorry I couldn't answer the other night, I was busy watching the fights. (on here) LOL
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Quoting hercj:
456 do you think they will put together a recon for this system for Sunday or Monday?


I have not seen any flights schedule for the weekend.
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Nite all...
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Quoting alexhurricane1991:
No im not convinced yet it could go either way but right now all i see is just remnant moisture sreaming into your area.


Keep in mind that weak, sheared disturbance in post 1506 does not imply a tropical system. The remnant moisture you pointed to is more or a less a disturbance.
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1526. hercj
456 do you think they will put together a recon for this system for Sunday or Monday?
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Quoting Weather456:


Yeah, been saying that all night. And when I said the GFS was being reasonable, it did not allow the system to organized because of the conditions in the GOM.
Oh okay thanks for the clarification.
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1524. xcool
oh really
Member Since: September 26, 2009 Posts: 2 Comments: 15626
Quoting FIU2010:

still not convinced, eh?
No im not convinced yet it could go either way but right now all i see is just remnant moisture sreaming into your area.
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1522. Drakoen
Microwave pass:

Member Since: October 28, 2006 Posts: 57 Comments: 29928
Quoting alexhurricane1991:
But do you think it will have time to organize into something? i mean when it traverses over central america its going to take a beating.


Yeah, been saying that all night. And when I said the GFS was being reasonable, it did not allow the system to organized because of the conditions in the GOM.
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1520. xcool
lmaoo
Member Since: September 26, 2009 Posts: 2 Comments: 15626
Quoting Grothar:


I studied the Kpelle tribe in Africa many years ago. They don't have a number higher than 3 and no measurements. When ask how far a place is, they answer "not far" if it is close; and "very far" if it a long distance. All in all not a bad system. However, I think they would be able to come closer to how many barrels of oil is seeping out than BP is doing!!!


That kinda sounds like when you're in the countryside in Jamaica. when they tell you "just around the corner" it could be a very long drive!
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Quoting xcool:
TampaSpin :0


In Chat room now.
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Quoting Skyepony:


Even over WindSat? That one covers it seems 1/2 or less than what ASCAT sees in a day.


Forgot that. I use Windsat much less than ASCAT because upon until recently, Windsat had half the globe blank for several weeks.
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1514. EricSFL


Hey FIU2010...

(from miami new times)
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1513. xcool
TampaSpin :0
Member Since: September 26, 2009 Posts: 2 Comments: 15626
Quoting xcool:
TampaSpin hey friend...


Hey Xcool!
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1511. Grothar
Quoting kimoskee:
Knock Him Dowm Man Don't Commit Murder
K H D M D C M

Kilo Heca Deca Metre Deci Centi Milli

That's how I remember. High school was a long time ago!


I studied the Kpelle tribe in Africa many years ago. They don't have a number higher than 3 and no measurements. When ask how far a place is, they answer "not far" if it is close; and "very far" if it a long distance. All in all not a bad system. However, I think they would be able to come closer to how many barrels of oil is seeping out than BP is doing!!!
Member Since: Posts: Comments:
Quoting Weather456:
The 00Z GFS is reasonable showing a weak, sheared disturbance moving towards the NE GOM, bringing rains to parts of FL and the SE before merging with a frontal system.
But do you think it will have time to organize into something? i mean when it traverses over central america its going to take a beating.
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Well the joke is on the other side too

I mean with something called "topkill" I thought for certain Cheney was involved

;)
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1508. Skyepony (Mod)
Quoting Weather456:


Frankly, I hate ASCAT. I would exhaust all other possible means before going to ASCAT. Not telling anyone ASCAT isn't good when its ready...but I am not feeling it, if u kno what i mean.


Even over WindSat? That one covers it seems 1/2 or less than what ASCAT sees in a day.
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1507. xcool
TampaSpin hey friend...
Member Since: September 26, 2009 Posts: 2 Comments: 15626

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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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