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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1057. cg2916
Quoting Hurricanes101:


LO means Low I would think
DB means Disturbance

In other words the NHCs thinking that the center is still not well-defined is correct


Look at my ASCAT pic:



How is that not well-defined? That's better than earlier.
Member Since: December 21, 2007 Posts: 13 Comments: 3035
hey is that a little bit of lower land between Chiapas range and the highlands in you image Weather456
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Quoting cg2916:
Now look at this:

28/2345 UTC 14.1N 95.9W T1.0/1.5 90E
28/1745 UTC 13.4N 94.7W T1.5/1.5 90E


yup and satellite confirms, 90E is getting less organized again

This system can't seem to get its act together enough
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1054. IKE
Quoting FIU2010:
ike, you watching the cane special?


Nope...watching the NBA.
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1053. cg2916
Now look at this:

28/2345 UTC 14.1N 95.9W T1.0/1.5 90E
28/1745 UTC 13.4N 94.7W T1.5/1.5 90E
Member Since: December 21, 2007 Posts: 13 Comments: 3035
Quoting cg2916:


It was LO... I forgot what that means.


LO means Low I would think
DB means Disturbance

In other words the NHCs thinking that the center is still not well-defined is correct
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Quoting Hurricanes101:
EP, 90, 2010052900, , BEST, 0, 130N, 942W, 30, 1005, DB

hmmmm wonder if this means anything


I believe it means disturbance.
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1050. cg2916
Quoting Hurricanes101:
EP, 90, 2010052900, , BEST, 0, 130N, 942W, 30, 1005, DB

hmmmm wonder if this means anything


It was LO... I forgot what that means.
Member Since: December 21, 2007 Posts: 13 Comments: 3035
Quoting CyclonicVoyage:
BP out till Sunday now for an answer on the top kill, ARGGGGG.


In other words, it isn't working. They said they would know by last Thursday. They didn't say anything then, but brought in another ship full of mud. So they're going to try again, but I think it's safe to say their first try was a failure. So was the junk shot.

I guess they are going to try another top kill, maybe with higher pressure.
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1048. Ossqss
Quoting StormSurgeon:


No Way! It's a UFO! Call UFO Hunters and set up a Nat. Geo. special!


I think your correct LoL :) Etna here!





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Quoting Weather456:


The last part was humor.

Which part do you want me expand on?


LOL......hey man.
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Quoting Weather456:
General topography of the area of interest. The highest rainfall will likely occur along the windward slopes of the Chiapas mountains and Guatemalan highlands on the right side of the storm where onshore flow and orographic lift are greatest.





Thanks 456, now I understand that the expansion you were speaking of was regarding the expansion of the rainfall umbrella as a tropical system makes landfall. Obviously, Salina Cruz will see copius amounts of rainfall from 90E. Don't you think?
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EP, 90, 2010052900, , BEST, 0, 130N, 942W, 30, 1005, DB

hmmmm wonder if this means anything
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Quoting atmoaggie:

This was a light to moderate wind condition. Winds from a minimal TS would be enough wind to make the waves happen regardless of surface oil slick and break up the surface slick which would stop the effect.I don't think so, but even if it did modify anything about a TC, it would so minimal of forcing as compared to all of the other factors involved as to be undetectable.

In my honest opinion, the primary, and only significant concern of the marriage of oil slick and TC is that storm surge would deposit oil in places it would not get to otherwise. And booms, skimming, etc. would be unusable in any effort to stop it.


But in some areas the slick is metres thick, and the could be upwelling from the shallower subsurface areas. What about a very small hurricane heading over the dense slick? Would it expand, or strengthen?
Member Since: August 30, 2008 Posts: 8 Comments: 2835
BP out till Sunday now for an answer on the top kill, ARGGGGG.
Member Since: January 30, 2010 Posts: 0 Comments: 3259
Quoting atmoaggie:
Like the new avatar...EC made some big changes to CMC before last season. Vastly improved. Will it hold? I dunno. Models tend to do well for one season and notsowell in another, it seems.
Tough to figure which is the one to look at in May. Ask again in September...


Ha, you guys are too funny. Avatar was an epic and amazing movie by the way.
Member Since: August 30, 2008 Posts: 8 Comments: 2835
Quoting StormSurgeon:


Huh? Expand please.


The last part was humor.

Which part do you want me expand on?
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Quoting KEEPEROFTHEGATE:

Interesting. And AMSR-E can detect SST through clouds most of the time...(but comes with land-interference, resolution, and revisit caveats).

Do they perchance have a plot showing the age of the pixels (called latency, in the business) in that plot?
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General topography of the area of interest. The highest rainfall will likely occur along the windward slopes of the Chiapas mountains and Guatemalan highlands on the right side of the storm where onshore flow and orographic lift are greatest.



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1037. KEEPEROFTHEGATE (Mod)
Quoting AstroHurricane001:


Slow-moving 90E has also used up a lot of the heat in the East Pacific. Some SSTs are down to 26C from 31C. One storm can affect the entire basin.
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Quoting Ossqss:
Off topic, but this is kinda cool. Volcanic Smoke Ring! Clickable picture

Cool!
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1034. IKE
And looking at the IR satellite on 90E...it looks headed toward that direction.
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Quoting Ossqss:
Off topic, but this is kinda cool. Volcanic Smoke Ring! Clickable picture :)





No Way! It's a UFO! Call UFO Hunters and set up a Nat. Geo. special!
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1032. pottery
Quoting AstroHurricane001:


So winds speed up over oil...does this mean that a hurricane's winds can intensify over the slick?! What will happen when the eyewall of a storm passes over the oil? Can the oil have an effect on the storm's trajectory speed?

Not really. The point was made re. a very calm sea condition at the time.
Sea conditions in a storm would be different as you know.
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1031. Ossqss
Off topic, but this is kinda cool. Volcanic Smoke Ring! Clickable picture :)



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1030. IKE
Quoting HurricaneObserver:
WRF Model shows 90E making it into the Caribean
myFOXHurricane


That's the same direction the other models that show it...have it going...on the eastern side of the Yucatan peninsula...heading N to NNE.
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Quoting AstroHurricane001:


So winds speed up over oil...does this mean that a hurricane's winds can intensify over the slick?! What will happen when the eyewall of a storm passes over the oil?

This was a light to moderate wind condition. Winds from a minimal TS would be enough wind to make the waves happen regardless of surface oil slick and break up the surface slick which would stop the effect.
Quoting AstroHurricane001:


Can the oil have an effect on the storm's trajectory speed?
I don't think so, but even if it did modify anything about a TC, it would so minimal of forcing as compared to all of the other factors involved as to be undetectable.

In my honest opinion, the primary, and only significant concern of the marriage of oil slick and TC is that storm surge would deposit oil in places it would not get to otherwise. And booms, skimming, etc. would be unusable in any effort to stop it.
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Quoting Weather456:



Tropical cyclones get larger due to land interaction, not the opposite...

I remembered Marco from 2008, it was a very small cyclone so it rained itself out quickly which may have made it appear smaller.

Marco was also small because it couldn't find polo.



Huh? Expand please.
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Quoting Weather456:



Tropical cyclones get larger due to land interaction, not the opposite...

I remembered Marco from 2008, it was a very small cyclone so it rained itself out quickly which may have made it appear smaller.

Marco was also small because it couldn't find polo.



Marco spun itself into a storm from a small vortex in the larger INVEST that moved over the Yucatan.

Smaller storms can also strengthen more rapidly as we saw with Cyclone Tracy north of Australia which held a record that Marco beat.

LOL!!!
Member Since: August 30, 2008 Posts: 8 Comments: 2835
WRF Model shows 90E making it into the Caribean
myFOXHurricane
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1025. Dakster
CMC = Constantly Making Cyclones -

When the other models start to agree that a Hurricane is going to hit South Florida, I'll put some effort into believing it.

Best thing is to have a model predict you will get hit 168 hours+ out. Statistically speaking, you are very safe...
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Quoting atmoaggie:
Like the new avatar...EC made some big changes to CMC before last season. Vastly improved. Will it hold? I dunno. Models tend to do well for one season and notsowell in another, it seems.
Tough to figure which is the one to look at in May. Ask again in September...


I'm sure there will be PLENTY of data by then...
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Quoting KEEPEROFTHEGATE:
iam aware of that and in all liklyhood 90e gets the number just in case if lurches forward 100 miles then no number


Slow-moving 90E has also used up a lot of the heat in the East Pacific. Some SSTs are down to 26C from 31C. One storm can affect the entire basin.
Member Since: August 30, 2008 Posts: 8 Comments: 2835
Quoting WatchingThisOne:


Yup. I also tend to look a bit harder at the CMC at the 96 and 120 marks ... it seems to do better than the other models.


Yeah, I'll stretch it to 5 days if the atmospheric conditions are rather benign, but that's about it. The multitude of models have gotten out of control now. If I look at a spaghetti model I just get hungry....lol
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Quoting KEEPEROFTHEGATE:
iam aware of that and in all liklyhood 90e gets the number just in case if lurches forward 100 miles then no number
Like the new avatar...
Quoting BaltOCane:



in 2007 someone, can't remember who, said CMC= Constantly Making Cyclones... hehe...

but if they've gotten better, then that should be interesting; it's 144 hours out
EC made some big changes to CMC before last season. Vastly improved. Will it hold? I dunno. Models tend to do well for one season and notsowell in another, it seems.
Tough to figure which is the one to look at in May. Ask again in September...
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Quoting plywoodstatenative:
1008 mb low at this time of the year in the Yucatan. aye yi yi.


You mean such a storm is actually rare? What about Arlene 2005 (wow I am spewing out a lot of analog storms)!
Member Since: August 30, 2008 Posts: 8 Comments: 2835
Quoting Weather456:



Tropical cyclones get larger due to land interaction, not the opposite...

I remembered Marco from 2008, it was a very small cyclone so it rained itself out quickly which may have made it appear smaller.

Marco was also small because it couldn't find polo.



LOL!
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1018. Makoto1
Quoting Weather456:



Marco was also small because it couldn't find polo.



rofl Polo was in the Pacific, that's why. It found the wrong ocean. It figured crossing Mexico would find it in the Pacific, but it found the BOC instead and when it hit land again it must have been very confused.
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Quoting atmoaggie:

Part of what Dr. M surmised in that post is that the roughness of wave action, though fairly small, created slightly more drag over the water-only surface and less over the oil slick. Then the winds over the oil slick would be slightly faster than the winds over water alone.

Simply put, a region of faster winds catching up to a region of slower winds. When that happens the winds immediately there will speed up a little, horizontally, but this is also a convergence zone, much as a shallow cold front can be, thus, the winds impart their momentum, some, to an upward direction. Surface air goes up, clouds form.

He did not ascribe the clouds being present to a difference in absorption of solar radiation, but could also be a factor, IMO. End result would be a small, weak version of the same seabreeze effect (without the usual T-storms) we see along coastlines all around this time of year.

And welcome aboard...I recommend thick skin, sharp wit, and developing the ability to speed skim over 20 posts of drivel to find one worth carefully scrutinizing.


So winds speed up over oil...does this mean that a hurricane's winds can intensify over the slick?! What will happen when the eyewall of a storm passes over the oil? Can the oil have an effect on the storm's trajectory speed?
Member Since: August 30, 2008 Posts: 8 Comments: 2835
Quoting Weather456:



Tropical cyclones get larger due to land interaction, not the opposite...

I remembered Marco from 2008, it was a very small cyclone so it rained itself out quickly which may have made appear smaller.

Marco was also small because it couldn't find polo.


Zing!
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Dang Atmo, don't confuse the guy.......or gal.
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Quoting AstroHurricane001:


Wow, those are some big waves. 90E is a fairly large system but may become smaller due to land interaction (remember Marco?).



Tropical cyclones get larger due to land interaction, not the opposite...

I remembered Marco from 2008, it was a very small cyclone so it rained itself out quickly which may have made it appear smaller.

Marco was also small because it couldn't find polo.

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Quoting StormSurgeon:


No models do. 72 hours is my personal model accuracy barometer.


Yup. I also tend to look a bit harder at the CMC at the 96 and 120 marks ... it seems to do better than the other models.
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1012. KEEPEROFTHEGATE (Mod)
Quoting leo305:





it will not make landfall tonight.. the thing is moving at a mile an hour.. and its around 100 miles off shore
iam aware of that and in all liklyhood 90e gets the number just in case if lurches forward 100 miles then no number
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Quoting leo305:


yep that is the CMC (which has been somewhat reliable)



in 2007 someone, can't remember who, said CMC= Constantly Making Cyclones... hehe...

but if they've gotten better, then that should be interesting; it's 144 hours out
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1008 mb low at this time of the year in the Yucatan. aye yi yi.
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Quoting WatchingThisOne:


GFS does not have a strong track record 15 days out :-)


No models do. 72 hours is my personal model accuracy barometer.
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1008. leo305
Quoting BaltOCane:
http://moe.met.fsu.edu/cgi-bin/cmctc2.cgi?time=2010052812&field=Sea+Level+Pressure&hour=Ani mation

this is interesting


yep that is the CMC (which has been somewhat reliable)
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1007. Makoto1
Quoting KEEPEROFTHEGATE:
because of land interaction it may not even get classified as systems are very rarly named at landfall or over land before classification is possible


Well it's moving so slowly that landfall is still a day or two away... If it doesn't get classified though it's still basically a major rain event so if I'm wrong it's not like much changes.
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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.