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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2907. Patrap
Member Since: Posts: Comments:
Quoting FIU2010:
KMan, ever been to the Americas?
Which one ?
Member Since: Posts: Comments:
Quoting SevereHurricane:
How much more similar can it get?






Well, at least there is some good news...most of the Caribbean and Gulf aren't as warm as it was in 2005 at this time of year.
Member Since: August 30, 2008 Posts: 8 Comments: 2835
Member Since: September 2, 2009 Posts: 130 Comments: 21091
2903. Patrap
Member Since: Posts: Comments:
2902. EricSFL
Quoting FIU2010:
KMan, ever been to the Americas?


I guess you mean MAINLAND American Continent...lol
Member Since: Posts: Comments:
Quoting MrstormX:


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.


You mean from the Gulf Stream?
Member Since: August 30, 2008 Posts: 8 Comments: 2835
2900. EricSFL
Quoting scott39:
I know ive asked this before, but what is keeping it from going closer to the BOC?


I believe there is an anticyclone currently positioned over the western Gulf.
Member Since: Posts: Comments:
000
WTPZ31 KNHC 292338
TCPEP1
BULLETIN
TROPICAL STORM AGATHA INTERMEDIATE ADVISORY NUMBER 3A
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP012010
500 PM PDT SAT MAY 29 2010

...AGATHA GRADUALLY MOVING INLAND OVER THE GUATEMALA/MEXICO
BORDER...TORRENTIAL RAINS SHOULD CONTINUE...


SUMMARY OF 500 PM PDT...0000 UTC...INFORMATION
----------------------------------------------
LOCATION...14.8N 92.1W
ABOUT 20 MI...30 KM...E OF TAPACHULA MEXICO
MAXIMUM SUSTAINED WINDS...40 MPH...65 KM/HR
PRESENT MOVEMENT...NE OR 55 DEGREES AT 10 MPH...16 KM/HR
MINIMUM CENTRAL PRESSURE...1003 MB...29.62 INCHES


WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY...

NONE.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT...

A TROPICAL STORM WARNING IS IN EFFECT FOR...
* THE PACIFIC COASTS OF EXTREME SOUTHEASTERN MEXICO...ALL OF
GUATEMALA...AND ALL OF EL SALVADOR FROM BOCA DE PIJIJIAPAN MEXICO
SOUTHEASTWARD TO THE EL SALVADOR-HONDURAS BORDER. THESE WARNINGS
WILL LIKELY BE DISCONTINUED LATER TONIGHT.

FOR STORM INFORMATION SPECIFIC TO YOUR AREA OUTSIDE UNITED
STATES...PLEASE MONITOR PRODUCTS ISSUED BY YOUR NATIONAL
METEOROLOGICAL SERVICE.


DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
AT 500 PM PDT...0000 UTC...THE CENTER OF TROPICAL STORM AGATHA WAS
LOCATED INLAND NEAR LATITUDE 14.8 NORTH...LONGITUDE 92.1 WEST.
AGATHA IS MOVING TOWARD THE NORTHEAST NEAR 10 MPH...16 KM/HR. THIS
GENERAL MOTION IS FORECAST TO CONTINUE THROUGH TONIGHT AND ON
SUNDAY. ON THE FORECAST TRACK...AGATHA WILL CONTINUE TO MOVE
FARTHER INLAND OVER CENTRAL AMERICA.

MAXIMUM SUSTAINED WINDS HAVE DECREASED TO NEAR 40 MPH...65
KM/HR...WITH HIGHER GUSTS. AGATHA IS EXPECTED TO WEAKEN FURTHER
OVER THE HIGH TERRAIN OF CENTRAL AMERICA.

TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 80 MILES...130 KM
PRIMARILY OVER WATER TO THE SOUTHEAST OF THE CENTER.

ESTIMATED MINIMUM CENTRAL PRESSURE IS 1003 MB...29.62 INCHES.


HAZARDS AFFECTING LAND
----------------------
WIND...TROPICAL STORM-FORCE WINDS ARE EXPECTED TO CONTINUE ALONG THE
COASTAL SECTIONS OF GUATEMALA. THESE WINDS SHOULD GRADUALLY BEGIN
TO SUBSIDE.

RAINFALL...DESPITE WEAKENING...THIS SYSTEM IS EXPECTED TO PRODUCE
TOTAL RAIN ACCUMULATIONS OF 10 TO 20 INCHES OVER EXTREME
SOUTHEASTERN MEXICO...GUATEMALA...AND MUCH OF EL SALVADOR...WITH
POSSIBLE ISOLATED MAXIMUM AMOUNTS OF 30 INCHES THROUGH SUNDAY.
THESE RAINS COULD CAUSE LIFE-THREATENING FLASH FLOODS AND MUD
SLIDES. THE METEOROLOGICAL SERVICE OF GUATEMALA HAS REPORTED UP TO
14 INCHES OF RAIN DURING THE PAST FEW DAYS.

STORM SURGE...THE METEOROLOGICAL SERVICE OF EL SALVADOR HAS REPORTED
THAT LARGE WAVES WERE AFFECTING THE COAST. FLOODING AND LARGE
WAVES CURRENTLY OCCURRING TO THE SOUTHEAST OF THE CENTER IN AREAS
OF ONSHORE FLOW SHOULD BEGIN TO GRADUALLY DECREASE.


NEXT ADVISORY
-------------
NEXT COMPLETE ADVISORY...800 PM PDT.

$$
FORECASTER AVILA/CANGIALOSI
Member Since: September 2, 2009 Posts: 130 Comments: 21091
Quoting Hurricanes101:


What wave?


The area of high potential vorticity near Yemen-Somalia.
Member Since: August 30, 2008 Posts: 8 Comments: 2835
Quoting HurricaneSwirl:
Hey does anyone have the table graphic that shows some sort of time line of average Atlantic hurricane activity? It shows when we should get our first storm, second, etc. along with hurricanes and major hurricanes for an average season. I had it in my bookmarks but it's invalid or something now. Also, does anyone have one of those for the East Pacific?


From NHC Tropical Cyclone Climatology
Member Since: September 23, 2005 Posts: 14 Comments: 10883
2895. scott39
I thought i read earlier that 456 said, that something is steering it more N, what is keeping it from going more NNW?
Member Since: Posts: Comments:
Quoting scott39:
I know ive asked this before, but what is keeping it from going closer to the BOC?
I really don't have an answer to that. I genuinely don't know.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
Quoting EricSFL:


I really don't think it will stay "intact". Even Katrina lost some of its power over very flat (and swampy) South Florida.
Yeah, bad wording on my part.
Quoting gordydunnot:
Lucky this went ashore when it did, inflow and outflow look perfect.In the rainbow loop classic signature for this storm.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
Quoting Patrap:


The SHA anomaly appears to be piling up right against the spill.
Member Since: August 30, 2008 Posts: 8 Comments: 2835
2890. Patrap
Click the TFP box for the NHC Track on the floater Loops.and the MSLP one too
Member Since: Posts: Comments:
2889. scott39
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.
I know ive asked this before, but what is keeping it from going closer to the BOC?
Member Since: Posts: Comments:
2888. RTLSNK
Looks like a stormy night for a lot of us:
Member Since: Posts: Comments:
Quoting scott39:
Is there anyway it wont encounter too many mountains?


No way around the Sierra Madre.

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2885. Patrap
Agatha Floater - Water Vapor Loop
Member Since: Posts: Comments:
Quoting CybrTeddy:
If Agatha made landfall this early then she's taken the more easterly influence of the model spectrum. Watch for an Alma/Arthur setup.. if not still Agatha will deliver heavy rains and even worse, mudslides.


Maybe Agatha will be another retired TS, like Alma!
Member Since: August 30, 2008 Posts: 8 Comments: 2835
2883. EricSFL
Quoting MiamiHurricanes09:
It has a better cloud signature and stronger convection, this might help it keep in tact over it's journey through central America and the Yucatan.


I really don't think it will stay "intact". Even Katrina lost some of its power over very flat (and swampy) South Florida.
Member Since: Posts: Comments:
Lucky this went ashore when it did, inflow and outflow look perfect.In the rainbow loop classic signature for this storm.
Member Since: Posts: Comments:
Quoting scott39:
Is there anyway it wont encounter too many mountains?
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.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
Hey does anyone have the table graphic that shows some sort of time line of average Atlantic hurricane activity? It shows when we should get our first storm, second, etc. along with hurricanes and major hurricanes for an average season. I had it in my bookmarks but it's invalid or something now. Also, does anyone have one of those for the East Pacific?
Member Since: Posts: Comments:
2879. Patrap
Caribbean and Gulf of Mexico Operational Data
Member Since: Posts: Comments:
2877. scott39
Quoting kmanislander:


Over water and low lying land but not over mountainous terrain like Guatemala. Once the system starts the climb up the mountains the circulation will decouple fairly quickly and the low level portion of it will go off in a different direction from the mid and upper levels.
Is there anyway it wont encounter too many mountains?
Member Since: Posts: Comments:
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.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
2874. scott39
Quoting kmanislander:


Over water and low lying land but not over mountainous terrain like Guatemala. Once the system starts the climb up the mountains the circulation will decouple fairly quickly and the low level portion of it will go off in a different direction from the mid and upper levels.
Thanks
Member Since: Posts: Comments:
Quoting FIU2010:
early july, huh, 456? do you ahve any prelimanry indications of what the steering pattern MIGHT be in early july in our basin, weather?


near impossible to know at this time.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting stormwatcherCI:
It has a better cloud signature and stronger convection, this might help it keep in tact over it's journey through central America and the Yucatan.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
2871. leo305
yikes..

http://www.cnn.com/2010/US/05/29/us.gulf.oil.spill/index.html?hpt=T1&iref=BN1

so top kill is a complete failure.. that really isn't good news..
Member Since: April 17, 2010 Posts: 0 Comments: 1753
Quoting scott39:
Does convection help keep the COC together?


Over water and low lying land but not over mountainous terrain like Guatemala. Once the system starts the climb up the mountains the circulation will decouple fairly quickly and the low level portion of it will go off in a different direction from the mid and upper levels.
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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.
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2867. Patrap
Floater - Rainbow Color Infrared Loop
Member Since: Posts: Comments:
Quoting Dakster:


really... Is this the 2012 pre-season warm up or what?

Lol. I wonder if the 2012 hurricane season is going to be a major bust or hyperactive.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
Member Since: Posts: Comments:
Good Evening Everyone!
Member Since: September 7, 2008 Posts: 17 Comments: 1604
Quoting FIU2010:


then normaL? but the carib. is in its rainy season, therefore, isn't taht to eb expected?
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.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
2860. scott39
Quoting kmanislander:


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.
Does convection help keep the COC together?
Member Since: Posts: Comments:
2859. Patrap
2km Storm Relative IR Imagery with BD Enhancement Curve

2km Storm Relative IR Imagery with BD Enhancement Curve

The same infrared imagery shown in the earth relative framework is displayed in a storm relative framework, with a 2km resolution and enhanced with the "BD Curve" which is useful for directly inferring intensity via the Dvorak Enhanced IR (EIR) technique. Scaling is provided by two lightly hatched circles around the center. The two circles have radii of 1 and 2 degrees latitude, respectively.

Member Since: Posts: Comments:
2858. Dakster
Quoting MiamiHurricanes09:
I know 2012 is getting close, but... LOL.


really... Is this the 2012 pre-season warm up or what?

Member Since: Posts: Comments:
2857. Levi32
Quoting FIU2010:


then normaL? but the carib. is in its rainy season, therefore, isn't taht to eb expected?


Yes, but their rainy season is expected to be wetter than normal this year.
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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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