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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1207. pottery
Quoting Bordonaro:

So, I gather the Calabash Tree was correct!

Welcome to Rainy Season 2010 in Trinidad and Tobago :o)!!
All is as it should be, here.
But we got up to 10" in parts of the Island on Wed night, which caused some pretty severe flooding...
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Quoting alexhurricane1991:
You got that right!
Agreed.
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Quoting stormwatcherCI:
Yes, but we are not getting any in Cayman yet.
Incroyable!
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Quoting BenBIogger:
GFS at 120 hours show a weak tropical storm in the southeastern Gulf of Mexico.
Shear is way too high in the area to support development.
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1203. KEEPEROFTHEGATE (Mod)
Quoting WinterAnalystwx13:


I'm not scaring anyone. Did I say a Category 5 would enter the Gulf and destroy anything? No. I only have it as a TD in the Gulf, and that is my opinion.
iam not trying to give ya a hard time
but right now there is enough worries in the gulf and to give any additional worries is not right thats all
we are watchin all of us and if something is gonna be a problem then it would be the right time to inform but at this time there is no reason for it
Member Since: July 15, 2006 Posts: 178 Comments: 55971
Quoting Weather456:


hey xcool...It was just last night I said to myself, you are one of those bloggers whose names describe them...in your case, a blogger of few words, cool and mellow.
You got that right!
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GFS at 120 hours show a weak tropical storm in the southeastern Gulf of Mexico.
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Quoting Weather456:


hey xcool...It was just last night I said to myself, you are one of those bloggers whose names describe them...in your case, a blogger of few words, cool and mellow.
You see, I'm different. I have a long username and I speak a lot. lol.
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1199. xcool



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Quoting xcool:
Weather456 hey


hey xcool...It was just last night I said to myself, you are one of those bloggers whose names describe them...in your case, a blogger of few words, cool and mellow.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting Hurricanes101:
wait wait wait

90E is NO THREAT to the US at this time and it is very likely it never will be

Lets not put up misinformation on here


The threat is to Central America right now due to flooding rains out the mountains, anything after that is nothing more than speculation
Yep i dont think 90E or whatever comes from it will be that big of a deal when it gets on our side but guatamala and surrounding countries are going to be in extreme rain fall because of the slow movement of this storm that will be the main headline with this disturbance soon to be td1E.
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Quoting pottery:

So, basically, from New York to Guyana?
Good coverage, anyway...
The graph I posted is based on direct landfalls. I doubt we will get a tropical cyclone making a direct landfall in Guyana or New York.
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1195. xcool



in GOM
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1193. pottery
Quoting AstroHurricane001:


I wouldn't rule out western Florida, Honduras and Nicaragua, Long Island to Massechusetts, Nova Scotia to Newfoundland, Guyana, and especially the Carolinas, as possible danger zones.

So, basically, from New York to Guyana?
Good coverage, anyway...
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Make sure you are prepared for hurricane season


by W456
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting Chicklit:

Um...the Caribbean bloggers did say they wanted rain...
Yes, but we are not getting any in Cayman yet.
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Quoting pottery:

We just all on the ball here, man!
I need more manpower around here these days, the grass, weeds, everything is growing faster than we can keep it back.
Thought I saw a Tiger stalking a Elephant in the yard the other day. Coulnt be sure. Too much bush....

So, I gather the Calabash Tree was correct!

Welcome to Rainy Season 2010 in Trinidad and Tobago :o)!!
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1188. xcool
Weather456 hey
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1187. hydrus
Quoting StormW:


Me! LOL!!
You would be a superb replacement.
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Quoting Weather456:


And we got

Well congrats on the rain i just hope theres no widespread flooding anywhere.
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1184. xcool
18 gfs storms in gom wt]]]]]]
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(Quoting Weather456): And we got . . .

Yippee! Rain glorious rain.
Now can someone turn the spigot off?!
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wait wait wait

90E is NO THREAT to the US at this time and it is very likely it never will be

Lets not put up misinformation on here


The threat is to Central America right now due to flooding rains out the mountains, anything after that is nothing more than speculation
Member Since: March 10, 2010 Posts: 1 Comments: 7874
This is a cool link. Check it out:

NextSat
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Quoting Chicklit:

Um...the Caribbean bloggers did say they wanted rain...


And we got

Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting xcool:
alexhurricane1991 heyyy
Hey Xcool!!!!
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Co -Cirrus overspread
CDO - Central dense Overcast
OBA - outer band area
ECT - embedded cloudtops

Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting Chucktown:


He was introduced last weekend and talked a little about 90L - very clear and concise, should fit in fine.
Okay thats good i didnt see him thank you
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1176. xcool
alexhurricane1991 heyyy
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Um...the Caribbean bloggers did say they wanted rain...
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Quoting MiamiHurricanes09:
Good evening!
Good evening to you as well!
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Quoting MiamiHurricanes09:


I wouldn't rule out western Florida, Honduras and Nicaragua, Long Island to Massechusetts, Nova Scotia to Newfoundland, Guyana, and especially the Carolinas, as possible danger zones.
Member Since: August 30, 2008 Posts: 8 Comments: 2835
1172. xcool
FIU2010 oh really mean ???
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Quoting alexhurricane1991:
Rick Knabb he worked at the NHC for 14 years so lets see how he does


He was introduced last weekend and talked a little about 90L - very clear and concise, should fit in fine.
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troughs are bad, ridges are good...right? Can anyone explain how these relate to hurricane formation/intensity? tia
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Good evening!
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1167. xcool
whats last news on 90e ????????????????
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Quoting stormhank:
Whos going to take Steve Lyons place at TWC???
Rick Knabb he worked at the NHC for 14 years so lets see how he does
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Excerpt: Latest National Hurricane Center Tropical Weather Discussion

274
AXNT20 KNHC 282350
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT FRI MAY 28 2010

... TOTAL PRECIPITABLE WATER IMAGERY INDICATES VERY HIGH VALUES ACROSS THE ENTIRE CARIBBEAN AND AS A RESULT CONVECTIVE ACTIVITY IS LIKELY TO CONTINUE THROUGH THE WEEKEND.

THE ADDITION OF THE TROPICAL WAVE CURRENTLY MOVING ACROSS EASTERN VENEZUELA AND SUBSEQUENT FRACTURING OF ENERGY AND MOISTURE N-NE FROM THE WAVE WILL ADD TO INCREASED PRECIPITATION OVER THE EASTERN AND CENTRAL CARIBBEAN.

AN UPPER LEVEL RIDGE AXIS ALSO EXTENDS FROM 11N56W TO 14N74W ALONG 14N TO AN AREA OF DISTURBED WEATHER IN THE E PACIFIC ALONG 95W. THIS UPPER LEVEL DIFFLUENCE ACROSS THE BASIN FURTHER SUPPORTS THE CONVECTION THIS EVENING.

BY SUNDAY...THE SURFACE TROUGHING ACROSS THE WESTERN CARIBBEAN IS FORECAST TO SHIFT INTO THE CENTRAL ATLC WITH SURFACE TROUGHING EXTENDING SW THROUGH THE MONA PASSAGE AND INTO THE CENTRAL CARIBBEAN.
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Whos going to take Steve Lyons place at TWC???
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Quoting atmoaggie:

But it will not be able to dampen waves created well out to sea where there isn't enough surface slick to stop them from forming. Then the mixing begins...

And the dense surface slick, covering square miles, will be staying about where it is until BP does something constructive, or at about 29 N. Very uncommon that we get very small hurricanes. (anyone know of any smaller than Camille in the northern gulf?)

Even if we got a little one, still would induce enough mixing that the surface oil would have an undetectable effect if any at all on the hurricane itself, again, in my honest opinion. Even the smallest cat 1 puts surface waters in motion. We all saw what happened when oil reached the loop current. A thin tendril stretched out over miles and miles. Moving water will do some things guaranteed to break up a solid slick.


Can a tropical cyclone form near or over the slick?
Member Since: August 30, 2008 Posts: 8 Comments: 2835
Quoting WeathermanAG:
I think 90E could be trouble for the Gulf Coast..Real Trouble!
We dont know that first off it has to survive the high terrain of guatamala then it has a very short time to organize because if it goes in the gulf it will be torn to shreds by shear this is your opinion but i dont see it being a big concern.
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Quoting stormhank:
?? Dr Lyons quitting weather channel???


He quit weeks ago - now the Meteorologist in Charge at the NWS office in San Angelo, TX.
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1158. tillou
KEEPEROFTHEGATE 1:41 AM GMT on May 29, 2010
Quoting WinterAnalystwx13:
I made this graphic really quickly.

and you really should stop scaring people nothing has been detemined yet with the system 90e

Thank you Keeperofthegate!!!!!
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Whats latest on 90E??? is it gonna affect the US in any way????
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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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