Loop Current Eddy cuts off; oil danger to Keys now greatly reduced
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
Reader Comments
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it will not make landfall tonight.. the thing is moving at a mile an hour.. and its around 100 miles off shore
I'm aware of that, however I think CFS was predicting in mid-May, a 1008 mb storm in the Yucatan Channel by June 8.
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.
thank u!
this is interesting
Oh ok. Phew I didn't read it wrong then. Lol. Still learning. :)
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.
yep that is the CMC (which has been somewhat reliable)
No models do. 72 hours is my personal model accuracy barometer.
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
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.
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.
Zing!
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?
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.
LOL!
You mean such a storm is actually rare? What about Arlene 2005 (wow I am spewing out a lot of analog storms)!
Tough to figure which is the one to look at in May. Ask again in September...
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
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.
I'm sure there will be PLENTY of data by then...
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...
myFOXHurricane
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!!!
Huh? Expand please.
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.
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.
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.
No Way! It's a UFO! Call UFO Hunters and set up a Nat. Geo. special!
Cool!
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?
The last part was humor.
Which part do you want me expand on?
Ha, you guys are too funny. Avatar was an epic and amazing movie by the way.
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?
hmmmm wonder if this means anything
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?
LOL......hey man.
I think your correct LoL :) Etna here!
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.
It was LO... I forgot what that means.
I believe it means disturbance.
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