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's wobbling a bit, but formed an eye at landfall.
But the upper level low and some convection could have survived? Same with Agatha. A LLC or two could develop from the remnant ULL.
Agree.
Billy Nungresser....President...Plaquemines Parish....
Doesn't think the gushing oil will be stopped until the relief wells are finished.
Do you release the subtropical jet stream is zonal and blowing at 40-50 knots while an upper anticyclone is vortex and blowing at 10-15 knots. The anticyclone will disrupt under that much zonal flow.
That's why the CMC makes no sense. It has the anticyclone buzz-sawing right through the Subtropical jet.
Say it fast with a Japanese B-Movie accent.
It works.
Konichi-wa
Agatha is capped by an upper anticyclone, not an upper low.
Now the LLC will likely tear apart over the terrain of CA but because the mountains are below 5500 ft, the mid-level circulation will survive. Again the mid-level circulation may become disrupted under to much west to east flow in the subtropical jet. The subtropical jet will not allow either an upper anticyclone nor mid-level circulation to persist since the force of the winds is in a straight-line.
Agatha's remnants could affect the oil spill.
It's speeding up.
Wave right behind it is even more impressive.
What wave?
I Like it too.
They steal all my junk..seems,
Im gonna get a good BP Lawyer.
I suspect if Agatha can at least hold together some kind of CoC like 90L did in 50kt shear, then it could potentially develop near the Eastern Seaboard with the help of low shear and SSts from the loop current.
nice blow up startin
Plus with the Caribbean looking more like early September than early June, it has about three more months than usual to warm to maximum temperature.
They defininately could not have been ready for all the hybrid storms this winter if they so wished to classify any of them as subtropical.
There are different types of highs.
You have shallow high pressures which only extend upward to about 600 mb the most. These highs are caused when cold air sinks to the surface and hugs it and since cold air is heavier than warm air, it creates high pressure. This type of high you would say is a low-level high pressure but we do not term them as such. The more familiar term is shallow high pressure. Examples include the North America High over Canada and the Siberian High over Asia.
We also have upper level highs caused by the expansion of heat in the tropics. These highs begin at around 500 mb and upwards. The subequatorial ridge of the tropics are example of this type of high. The high over Texas during July is another example of an upper high and the massive Tibetan high is the largest of them all.
You also have deep layer highs. These highs form from sinking air (subsidence) emanating from the outflow near the ITCZ and sinking towards the subtropics. These highs extend throughout most of the atmosphere and include the Azores High, Pacific High, St. Helena High, Australian High and the SE Pacific High.
2 degrees F,,my mistake
September 29, 2009
May 29, 2010
*And keep in mind that that was in 2009, and we all know 2009 wasn't an impressive year, it even wasn't "average".
I agree on that. I saw it in pretty much that position about 2 hours ago. No Sunday morning landfall for this one.
But its maximum temperature won't be any higher above normal than it is now, because the pattern is reversing to cloudier and wetter than normal in the Caribbean.
The volcano in Guatemala and the one in Ecuador erupted both in the same week. Now they're saying that the giant Katla volcano is due to erupt imminently in Iceland.
We've had landfall for a while now..
000
WTPZ61 KNHC 292234
TCUEP1
TROPICAL STORM AGATHA TROPICAL CYCLONE UPDATE
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP012010
340 PM PDT SAT MAY 29 2010
...CENTER OF AGATHA CROSSING THE COAST NEAR THE GUATEMALA/MEXICO
BORDER...
AT 340 PM PDT...2240 UTC...SURFACE OBSERVATIONS AND SATELLITE IMAGES
INDICATE THAT THE CENTER OF AGATHA IS CROSSING THE COAST ALONG THE
BORDER OF MEXICO AND GUATEMALA...AND IS NOW LOCATED JUST SOUTHEAST
OF TAPACHULA MEXICO.
That's landfall.
The real damage is yet to come though. Watch those thunderstorms blow up with the forcing that will take place on the upslopes. Night time will also help those high cloud tops cool down quickly thus enhancing the convection.
It could be a dry pocket, but it looks like an eye making landfall near the Mexico-Guatemala border popping up to the east of a sudden burst of convection in the CDO at landfall.
Viewing: 2801 - 2851
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