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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3757. xcool



54hr





162..
Member Since: Posts: Comments:
Hey guys new to the place. I'm currently an undergrad student and I want to get my masters in broadcast meteorology. Check out my 2010 Hurricane Forecast. I think this upcoming hurricane season will keep me coming back here often.
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3753. xcool



Member Since: Posts: Comments:
Quoting btwntx08:
and u can call me rob :)

you can call me "Al".
Member Since: Posts: Comments:
Quoting xcool:
icannot find it damm
Koritheman just said just look at the vertical shear forecasts
Member Since: April 8, 2010 Posts: 15 Comments: 2572
Quoting gulfcoastdweller:


best post of the Sunday Blog.......and it's early in the day!!!....but for you Aussie...LMAO!!

lol, 5:30pm sunday night here. Still waiting for heavy rain.
Member Since: Posts: Comments:
Quoting gulfcoastdweller:


ok with the 3726 post and ur post.....what does that mean? I am one who comes here looking for info. I know the basics but don't know as much as many here on this blog

I know we are in for a busy season and to add the "oil" issue too, I am worried. it's kinda funny/sad how ppl here in Biloxi are reacting to the NOAA outlook. Most have the feeling that since Katrina happened, they are good for another 30 years and think the NOAA outlook is BS and are with the mindset that they will deal with a storm when it happens. None of them have prepared or even are thinking about prep plans.

It just frustrates me no one can heed the warnings

Do you know of the Barometer Bob show, It's on Thursday at 8pm ET. The show this week had a guest, his name, David Dilley from Global Weather Oscillations Inc. They talked about regions that could be impacted this hurricane season. Very eye-opening stuff. You can download the podcast from here.
I was actually on the show on April 29 with my lightening strike story.
Hurricane Hollow is also a very informative website.
Member Since: Posts: Comments:
3747. xcool
hey alex ///// lmao crazy
Member Since: Posts: Comments:
Quoting xcool:
<< scott here
Hey scott!
Member Since: April 8, 2010 Posts: 15 Comments: 2572
3743. xcool
MRF models create the gfs
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3742. xcool
yeah alot too much
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3741. xcool
icannot find it damm
Member Since: Posts: Comments:
Quoting FIU2010:


no me grites, ok, CARAMBA.
Please stop asking questions that you know people have no idea what the answer is i beg of you please.
Member Since: April 8, 2010 Posts: 15 Comments: 2572
Quoting melwerle:
Aussie has NEVER SAID anything derogatory to anyone since I've been around. Always informative and polite...

Aussie IS da bomb...

Thanks
Member Since: Posts: Comments:
3735. xcool
<< scott here
Member Since: Posts: Comments:
Quoting xcool:
i need to check on subtropical jet models


There are no "subtropical jet models". That is determined simply by checking the vertical shear forecasts.
Member Since: Posts: Comments:
Quoting xcool:
alexhurricane1991 yeah.i'm try find models.i have 3,000 website
You can just call me alex i dont mind.
Member Since: April 8, 2010 Posts: 15 Comments: 2572
Quoting weathersp:


Blob of Mid-level/low level showers with wispy cirrus clouds by sunday.


I meant surface winds. As far as I can tell, there will be no appreciable pressure gradient as the system nears the Gulf of Mexico, and the convection will be minimal due to strong vertical shear. Hence, no strong surface winds.
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3731. xcool
alexhurricane1991 yeah.i'm try find models.i have 3,000 website
Member Since: Posts: Comments:
Quoting xcool:
i need to check on subtropical jet models
Yeah can you post them?
Member Since: April 8, 2010 Posts: 15 Comments: 2572
Quoting xcool:
i need to check on subtropical jet models

If I had to guess, I'd put my timestamp on around the first of July for it to start really clearing out (we need more heat to build up to really drive it north)
Member Since: Posts: Comments:
3728. xcool
i need to check on subtropical jet models
Member Since: Posts: Comments:
Quoting KoritheMan:


No, because there will be no strong winds to accompany it.


Blob of Mid-level/low level showers with wispy cirrus clouds by sunday.
Member Since: Posts: Comments:
Quoting gulfcoastdweller:


if it does bring heavy rains to Fl, even it tracking across the southern Gulf, will that engery be enough to cause the oil to push up farther to the coast lines?


No, because there will be no strong winds to accompany it.
Member Since: Posts: Comments:
Quoting FIU2010:


by when then, korith.
Too early too tell just be PATIENT!!!!
Member Since: April 8, 2010 Posts: 15 Comments: 2572
3722. xcool


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Quoting btwntx08:

i would agree other than that it will bring heavy rains to fl


Yeah. The subtropical jet will not be lifting within the next week and beyond.
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Agatha is crossing at one of the narrowest parts of Cental America. Once you get beyond the inital mountians, its all a coastal plain. And this is not hyping, its fact, you can't hype geography... and besides once it gets over (which I think it will, barely.) Then it will get ripped to shreads, eaten, swallowed then regurgitated by the shear.

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3719. xcool
FIU2010 .ok
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3718. xcool


Member Since: Posts: Comments:
Quoting hcubed:


Oh, no! Don't do anything darstic...


lol!!!
Member Since: Posts: Comments:
Quoting xcool:
KoritheMan I'm real tracks Storm but hit noo land


Oh, I'm certainly hoping for an Atlantic system to track, as well. I'm just saying that any potential for Agatha's regeneration is slim to none.
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3713. xcool
FIU2010 you go stop be so mean. im asking you..
Member Since: Posts: Comments:
Quoting FIU2010:
it kills it
And rightly so it is not looking to good for agatha but the problem is going to be the very heavy rainfall in central america.
Member Since: April 8, 2010 Posts: 15 Comments: 2572
3710. xcool
KoritheMan I'm real tracks Storm but hit noo land
Member Since: Posts: Comments:
Quoting StSimonsIslandGAGuy:
Good to see you melwerle :)
Good to see you stsimmonsislandGAguy!
Member Since: April 8, 2010 Posts: 15 Comments: 2572

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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.