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 Drakoen:


Western Caribbean then GOM. It pushes it straight into the subtropical jet stream while the CMC has it riding along it.
Oh yeah I see it. It just looked too weak so I really didn't bother of thinking of it as a possibility.
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Model initializations of 90E versus satellite-based center (blue dot).

They are still a bit off to the northeast. The system is elongated in that direction though.

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Quoting IKE:


GFDL does show something left of 90E coming off of the northern Yucatan.
Really?

GFDL 12z 78 Hours
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Quoting MiamiHurricanes09:
The GFDL isn't showing 90E getting into the Caribbean. Once it goes over the Yucatan it just kills it.

Link

I haven't seen the 12z HWRF yet, though.
Did you look at the GEM model?
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Quoting MiamiHurricanes09:
The GFDL isn't showing 90E getting into the Caribbean. Once it goes over the Yucatan it just kills it.

Link

I haven't seen the 12z HWRF yet, though.


Western Caribbean then GOM. It pushes it straight into the subtropical jet stream while the CMC has it riding along it.
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Quoting Jeff9641:


I respect that. The Miami is the trough out west, this trough is going to be the one to pick this system up.
I guess time will tell.
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300. IKE
Quoting MiamiHurricanes09:
The GFDL isn't showing 90E getting into the Caribbean. Once it goes over the Yucatan it just kills it.

Link

I haven't seen the 12z HWRF yet, though.


GFDL does show something left of 90E coming off of the northern Yucatan.
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Quoting WaterWitch11:
please tell me obama is going to visit other areas other than grand isle?!?


He has..the Blackhawk did a Expansive tour..Grand Isle is the Media point and focus.
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Quoting Drakoen:
So maybe 90E will get a chance to be in the Caribbean according to the CMC, GFDL, and HWRF 12z
The GFDL isn't showing 90E getting into the Caribbean. Once it goes over the Yucatan it just kills it.

Link

I haven't seen the 12z HWRF yet, though.
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Quoting Levi32:


Where were they getting that from? I didn't know the ECMWF did an Atlantic hurricane forecast.


Me neither
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294. IKE
Quoting WaterWitch11:
please tell me obama is going to visit other areas other than grand isle?!?


I was just thinking the same....watching on CNN.
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Quoting IKE:
I wouldn't bet my paycheck on the 12Z CMC being right. I see a much less aggressive area on the 12Z GFS. I would believe the GFS over the CMC.

Time will tell...that's what makes this fun.


Funny thing is the GFS isn't showing 90E approaching Florida, but an entirely different low. The CMC thinks it's 90E.
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292. IKE
Quoting nrtiwlnvragn:


No. Did you see the ECMWF seasonal numbers that someone posted earlier today? 18-28


No. I was busy....what is it saying?
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please tell me obama is going to visit other areas other than grand isle?!?
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Quoting nrtiwlnvragn:


No. Did you see the ECMWF seasonal numbers that someone posted earlier today? 18-28


Where were they getting that from? I didn't know the ECMWF did an Atlantic hurricane forecast.
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289. IKE
I wouldn't bet my paycheck on the 12Z CMC being right. I see a much less aggressive area on the 12Z GFS. I would believe the GFS over the CMC.

Time will tell...that's what makes this fun.
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Quoting nrtiwlnvragn:


No. Did you see the ECMWF seasonal numbers that someone posted earlier today? 18-28


Link please
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So maybe 90E will get a chance to be in the Caribbean according to the CMC, GFDL, and HWRF 12z

The upper level ridge axis will be over head in the Caribbean and the nose of the ridge may get into the southern GOM.
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Quoting IKE:
Believe it?


No. Did you see the ECMWF seasonal numbers that someone posted earlier today? 18-28
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Quoting Levi32:


Nope, but funny. I do believe this is one of those cases where the CMC is out to lunch. We shall see though.
If more models jump aboard then defiantly we have to watch it, but I am 99% sure no more models will agree.
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Quoting SevereHurricane:


Snow for Levi. lol


Ha don't I wish. Unfortunately 540 thicknesses don't give us snow here the way they do for you in the lower 48 :P
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Quoting Jeff9641:


True and I agree with you it's moisture will come over Florida once this trough out west moves east.
I don't think the moisture will come to Florida.
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Quoting IKE:
Believe it?


LOL, too funny. I do believe this is one of those cases where the CMC is out to lunch. We shall see though.
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Quoting Jeff9641:


Thanks IKE I feel as if I have been beating a dead horse for days. I have explained why this is going to happen until I can't explain anymore.



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Quoting Drakoen:


LOL!!!


The CMC is back to its old self!
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Quoting Jeff9641:


This is for you!

http://www.nco.ncep.noaa.gov/pmb/nwprod/analysis/namer/gfs/12/fp0_192.shtml


Snow for Levi. lol
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Quoting IKE:
Believe it?


If it was 2005 - yes. Otherwise no. If 2010 is another 2005, then watch out.
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Quoting IKE:
Believe it?


LOL!!!
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Quoting Jeff9641:


I feel people don't look at models before they speak. I think they think I'm making this up.
I don't think you're making it up, but the GFS looks like it is. You can't trust the GFS after 5 days.
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Quoting IKE:
Believe it?


OUCH, Good thing my answer is no.
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Quoting Jeff9641:


I feel people don't look at models before they speak. I think they think I'm making this up.


I think you're looking for something that isn't there. I looked which is why I posted you a map. Look at your own 4-panel link. The surface low is on the northern side of the subtropical jet under 70 knots of westerlies. Not only that, but it's baroclinic, with a temperature gradient to its north and it's attached to a front.
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Quoting IKE:
Believe it?


Nice...
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Quoting IKE:
Believe it?
I do not believe it. And what is interesting is that it strengthens even though it is right in the subtropical jetstream.
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265. IKE
Believe it?
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Quoting Jeff9641:


This is for you!

http://www.nco.ncep.noaa.gov/pmb/nwprod/analysis/namer/gfs/12/fp0_192.shtml
Notice that is at 192 hours. 90E by that time will be non-existent due to the proximity to land.
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so i see the buttons for:
plus, minus, flag and hide but where is button for having the iq of a provolone?

yes i know it's not fair to that beautiful cheese!
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misposted
Member Since: August 21, 2007 Posts: 0 Comments: 4860
Quoting IKE:
GFS @ 12Z through 144 hours.


The GFS keeps 90E over the eastern Pacific near the coast of Guatemala, and eventually dissipates it in several days, likely due to proximity to land.
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90E looking good.



Possible slow eastward motion can be noted on satellite animation.
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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.