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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There are 5 people dead already in Guatemala due to floods from Agatha.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting JLPR:


I'm sending a cookie right away!
want a chocolate chip one or with raisins? XD
Oatmeal please, lol.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
3005. JamesSA
Quoting Patrap:
TFP'S just updated on the track inland, Agatha Floater - Water Vapor Loop


Slows her down in speed track wise dramatically..

There is already convection popping up on the Gulf off Honduras side. I say she may re-develop on the Caribbean side.
Member Since: Posts: Comments:
Very rare and very nice image we've got here:

Member Since: September 2, 2009 Posts: 130 Comments: 21091
Quoting MiamiHurricanes09:
Is there a graph that shows forecasted steering?


You can use the steering maps at PSU. Other proxies for steering include 1000-500 mb average winds, water vapor imagery and climatology.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
3002. JLPR
Quoting MiamiHurricanes09:
Is there a graph that shows forecasted steering?

*Nice, I'm the first 3000th poster this year, do I win a cookie?


I'm sending a cookie right away!
want a chocolate chip one or with raisins? XD
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The South Florida forecast is allready calling for an increase chance of rain and wind by Wed Night
Member Since: August 26, 2009 Posts: 0 Comments: 412
Quoting Weather456:


The maps at CIMSS show the current steering. To know where a system will be in said amount of time, you have to consider that steering flow changes thus the forecasteed steering must apply.
Is there a graph that shows forecasted steering?

*Nice, I'm the first 3000th poster this year, do I win a cookie?
Member Since: September 2, 2009 Posts: 130 Comments: 21091
Quoting RyanCRG:
I havn't posted anything on this blog since last season. Some of you oldtimers here know me. I'm a former Hurricane researcher/chaser. This whole setup of Oil spill, currents, and favorable conditions for an extreme season has me terrified. God help the Gulf Coast and lets hope people start to take action. I'm monitoring the overall situation day by day on Facebook, and will return to regular commentary on this blog soon...
Ryan Keelan
Cyclone Research Group 04-08


Good to see you back Ryan....talked a bit with you a few years back...part of the FL Hurricane Emergency Response team here on the Gulf ourselves.
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I see convection starting to build up again in the bay of Honduras witch should help keep the system moist as it approaches the Caribbean also pressures have fallen a lot from last night
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Quoting cg2916:


It's really weakening.
To be expected over land.
Member Since: October 9, 2008 Posts: 0 Comments: 8279
Quoting MiamiHurricanes09:
Looking at that graph is why I don't understand why models take it towards the GOM and not towards the Caribbean.


The maps at CIMSS show the current steering. To know where a system will be in said amount of time, you have to consider that steering flow changes thus the forecasted steering must apply.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
I believe the last Jeff Masters blog which had over 3,000 comments was Sept 1, 2009, and this one will probably surpass the 3,500+ comments which were on Sept 1st blog.
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2994. cg2916
Quoting nrtiwlnvragn:
EP 01 2010053000 BEST 0 147N 921W 30 1003 TD


Users are also cautioned that the data in these files are subject to frequent revisions and can differ from information issued in official NHC products.


It's really weakening.
Member Since: December 21, 2007 Posts: 13 Comments: 3037
Quoting FIU2010:
what's that in the SW carib. at 100 hours, miami?
The imagination of the GFS at work, lol.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
Quoting belizeit:
Felix was a very strong hurricane whith only a very very small cloud field


So small that the 1.0 degree GFS only ever saw a 45 knot TS though Felix hit what? 140 knots? Both sides of eyewalls fit in between GFS grid points...
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Quoting atmoaggie:

By that, yeah, appears so.

When it gets to -2 by -2 in the octet plot is when we get 3 storms in the basin. That qualifies as strong, IMO.
I agree.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
Quoting AstroHurricane001:


Looking at the reverse direction, that's how Felix tracked. It got destroyed by the mountains.
Felix was a very strong hurricane whith only a very very small cloud field
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2988. cg2916
Quoting WinterAnalystwx13:


lol...Golf of Mexico.


It will be the Golf of Mexico after the Junk Shot.
Member Since: December 21, 2007 Posts: 13 Comments: 3037
EP 01 2010053000 BEST 0 147N 921W 30 1003 TD


Users are also cautioned that the data in these files are subject to frequent revisions and can differ from information issued in official NHC products.
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Quoting MiamiHurricanes09:
Well pretty strong if you ask me.


By that, yeah, appears so.

When it gets to -2 by -2 in the octet plot is when we get 3 storms in the basin. That qualifies as strong, IMO.
Member Since: Posts: Comments:
2984. RyanCRG
I havn't posted anything on this blog since last season. Some of you oldtimers here know me. I'm a former Hurricane researcher/chaser. This whole setup of Oil spill, currents, and favorable conditions for an extreme season has me terrified. God help the Gulf Coast and lets hope people start to take action. I'm monitoring the overall situation day by day on Facebook, and will return to regular commentary on this blog soon...
Ryan Keelan
Cyclone Research Group 04-08
Member Since: Posts: Comments:
Quoting MiamiHurricanes09:


Does the NHC really expect the storm to head back out to sea then make landfall farther southeast? Or is that the 8 pm position on the 5 pm cone? If so the storm is tracking farther west than expected and could end up in the BoC.
Member Since: August 30, 2008 Posts: 8 Comments: 2835
Quoting atmoaggie:

Strong? Not really...



And GFS will hopefully get better at this soon...for now, use the GEFS ensemble mean as *some* guidance.
Well pretty strong if you ask me.

Member Since: September 2, 2009 Posts: 130 Comments: 21091
Quoting cg2916:


How do you make those images?
Powerpoint and Google Earth. A lot of gradients used.
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2980. KEEPEROFTHEGATE (Mod)
01E/XX/A
MARK
14,5N/92.1W


MOVEMENT N
TRACK
15.6N/92.3W
16.3N/92.4W
16.9N/92.2W
17.1N/92.5W
17.9N/92.7W
18.1N/93.3W
STOP
Member Since: July 15, 2006 Posts: 169 Comments: 53296
Quoting Patrap:


Im pretty sure the Highs in the Late 70's were much stronger..

Ahemmm..
Yep. LOL
Member Since: October 9, 2008 Posts: 0 Comments: 8279
Quoting MiamiHurricanes09:
We are currently under the effects of a strong upward motion MJO that should stay around for a while, plus we have the monsoonal trough further north than normal, furthermore enhancing convection. Expect the Caribbean to not only be an area prone for development but a very moist one too.

Strong? Not really...



And GFS will hopefully get better at this soon...for now, use the GEFS ensemble mean as *some* guidance.
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2977. cg2916
Quoting cyclonekid:
TS Agatha Intermediate Advisory 3A





How do you make those images?
Member Since: December 21, 2007 Posts: 13 Comments: 3037
Quoting belizeit:
I thing if Agatha continues ne she has a big chance of surviving because she will cross the mountains tonight at DMAX and by morning she will be across the high mountains if she continues at 10 mph and by tommarrow night she will reach the carribean but whith out a name



A storm with no name. Wasnt there a song like that?
Member Since: August 26, 2009 Posts: 0 Comments: 412
2975. Patrap
Quoting atmoaggie:

You got the right idea. Surface lows and high are what usually appear of the analysis, but can behave differently depending on upper level conditions.


Im pretty sure the Highs in the Late 70's were much stronger..

Ahemmm..
Member Since: July 3, 2005 Posts: 421 Comments: 127664
Quoting MiamiHurricanes09:
If it continues ENE/NE motion into the Gulf of Honduras, it will encounter less mountains but none the less it will be a bumpy ride.


Looking at the reverse direction, that's how Felix tracked. It got destroyed by the mountains.
Member Since: August 30, 2008 Posts: 8 Comments: 2835
GFS 18z showing a piece of energy from Agatha emerging over by the extreme northwestern Caribbean, this area of convection later affects south Florida.

GFS 18z 48 Hours


Here at 102 hours there is a 1010 MB low over south Florida.

GFS 18z 102 Hours



Member Since: September 2, 2009 Posts: 130 Comments: 21091
2972. Patrap
.."Itsa Crude,crude Summer"...
Member Since: July 3, 2005 Posts: 421 Comments: 127664
hey guys there is a very good reason why Agatha moved further north than forecasted look closely on this map where Agatha is

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Quoting gordydunnot:
Thank you atmo as I often noticed they had highs on maps were there seemed to be ull and whatnot. So do you just use atmospheric layer maps to figure this out. Or is there and easy why to tell if they are stacked.

You got the right idea. Surface lows and high are what usually appear of the analysis, but can behave differently depending on upper level conditions.
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I thing if Agatha continues ne she has a big chance of surviving because she will cross the mountains tonight at DMAX and by morning she will be across the high mountains if she continues at 10 mph and by tommarrow night she will reach the carribean but whith out a name
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TS Agatha Intermediate Advisory 3A



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2966. Levi32
Quoting FIU2010:
levi, are we in-store for an active june and july?


It is likely they will be more active than normal, as will probably all months of this season.
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Quoting MiamiHurricanes09:
Bay of Campeche, that is located in the extreme southern Golf of Mexico.


Thank's
Member Since: August 26, 2009 Posts: 0 Comments: 412
Quoting AstroHurricane001:


I thought it was moving NNE? Or was that just a wobble?
Current movement is NE at 10 MPH.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
Quoting kuppenskup:
WHAT DOES BOC MEAN?
Bay of Campeche, that is located in the extreme southern Golf of Mexico.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
Quoting SiestaCpl:


oops...
"www.central-america-map.com/topo-map.htm"
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2960. Prgal
Quoting kuppenskup:
WHAT DOES BOC MEAN?


Bay of Campeche.
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Quoting Patrap:

"Oh no..there goes the Gulf of Mexico,,go-Go,Oil-Zilla..

whoooa,Oh"


Here is a Topo Map of the coastal area and mountains along the path of Agatha...
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Quoting MiamiHurricanes09:
After looking at satellite imagery Agatha is moving straight for the gulf of Honduras, hmmmm. I doubt this trend will continue, but hey, you never know.


I thought it was moving NNE? Or was that just a wobble?
Member Since: August 30, 2008 Posts: 8 Comments: 2835
WHAT DOES BOC MEAN?
Member Since: August 26, 2009 Posts: 0 Comments: 412

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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.