Oil spill headed towards the Loop Current
Recent satellite imagery and flight over-passes of the Gulf of Mexico oil spill confirm that a surface tendril of oil has become entrained into a southward-moving current that threatens to pull oil into the Gulf of Mexico Loop Current late this week. 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 then along the west side of the western Bahamas. Here, the waters of the Loop Current flow northward along the U.S. coast and become the Gulf Stream. Once oil gets into the Loop Current, the 1 - 2 mph speed of the current should allow the oil to travel the 500 miles to the Florida Keys in 10 - 20 days. Portions of the Loop Current flow at speed up to 4 mph, so the transport could be faster.
Why is oil getting close to the Loop Current?
The winds over the oil spill location are offshore out of the northwest today, and offshore winds will continue intermittently through Wednesday, helping push the oil southwards towards the Loop Current. However, the major reason oil is moving southwards is because of the instability of the currents in the Gulf of Mexico. The Loop Current is not a stable feature, and tends to surge northwards and southwards in a chaotic fashion, and in response to changes in the prevailing winds. Over the past week, chaotic behavior of the Loop Current and a clockwise-rotating eddy just to its north, just south of the oil spill location, have combined to bring a current of southward-moving surface water to the oil spill location. As strong on-shore winds from the southeast slackened this past weekend, oil has been drawn southward towards the Loop Current. An examination of the latest NOAA trajectory forecasts and surface current forecasts reveals the possibility that this tendril of southward-moving oil could make it into the Loop Current late this week. It is highly uncertain how much oil might make it into the Loop Current, or how diluted it might get on its voyage to the Florida Keys next week. Southeast to east winds of 10 - 15 knots are expected to develop late this week and extend into early next week, which may be strong enough to impose a surface current that will prevent oil from getting into the Loop Current this month. I predict a 30% chance that oil will make it into the Loop Current in the next two weeks.
Figure 1. Forecast made at 8pm EDT Sunday May 16, 2010, of the Gulf of Mexico currents by NOAA's HYCOM model. A persistent southward flowing surface current is predicted to occur this week between the oil spill location (red dot) and the Loop Current. Image credit: NOAA.
Likely areas of impact once oil gets into the Loop Current
Based on a study of 194 floating probes released into the Northeast Gulf of Mexico during a 1-year study in the 1990s (Figure 2), the west coast of Florida from Tampa Bay southwards to the Everglades is at minimal risk of receiving oil from surface currents. There is a "forbidden zone" off the southwest Florida coast where the shape of the coast, bottom configuration, and prevailing winds all act to create upwelling and surface currents that tend to take water away from the coast. This study implies that the greatest risk of land impacts by surface oil caught in the Loop Current is along the ocean side of the Florida Keys, and along the coast of Southeast Florida from Miami to West Palm Beach. Eddies breaking away from the Gulf Stream would also likely bring oil to northwest Cuba, the western Bahamas, and the U.S. East Coast as far north as Cape Hatteras, North Carolina, though at lesser concentrations. Southwest Florida cannot rest entirely, though--the "forbidden zone" is only true for surface waters, and there is onshore flow below the surface. Since recent ship measurements have detected substantial plumes of oil beneath the surface, southwest Florida might be at risk if one of these plumes gets entrained into the Loop Current. These subsurface plumes were also detected by current probes launched into the oil spill on May 8 by one of NOAA's hurricane hunter aircraft, according to one scientist I spoke to at last week's AMS hurricane conference. There are plans for the Hurricane Hunters to go out again tomorrow and drop more probes into the spill to attempt to get a better handle on where the oil is and where the currents are taking it.
Figure 2. Paths of 194 floating probes released into the yellow-outlined area in the northeast Gulf of Mexico between February 1996 and February 1997 as part of a study by the Mineral Management Service (MMS). The probes were all launched into waters with depth between 20 and 60 meters. Image credit: Yang, H., R.H. Weisberga, P.P. Niilerb, W. Sturgesc, and W. Johnson, 1999, Lagrangian circulation and forbidden zone on the West Florida Shelf, Continental Shelf Research Volume 19, Issue 9, July 1999, Pages 1221-1245 doi:10.1016/S0278-4343(99)00021-7
When will a Loop Current eddy break off?
Every 6 - 11 months, the looped portion of the Loop Current cuts off into a clockwise-rotating ring of water that then slowly drifts west-southwest towards Texas. When one of these rings breaks off at the peak of hurricane season, it provides a source of heat energy capable of providing fuel for rapid intensification of any hurricanes that might cross over. The Loop Current is not predicted to shed an ring over the next month, as predicted by the latest 1-month forecast from the U.S. Navy. However, the last eddy broke off in July of 2009, ten month ago, and it is unusual for the Loop Current to go more than eleven months without shedding an eddy. I expect we'll see the Loop Current shed an eddy in July or August, just in time to pose the maximum threat for hurricane season. According to an interesting February 2004 article published by offshore-engineer.com, reliable forecasts of these currents and eddies are not available yet. Keep in mind that surface currents are largely driven by winds, and wind forecasts are not reliable out more than about 10 days.
References
Yang, H., R.H. Weisberga, P.P. Niilerb, W. Sturgesc, and W. Johnson, 1999, Lagrangian circulation and forbidden zone on the West Florida Shelf, Continental Shelf Research Volume 19, Issue 9, July 1999, Pages 1221-1245 doi:10.1016/S0278-4343(99)00021-7.
Reader Comments
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That shows it clearly... it is more than just a rainbow sheen that has been pulled into the loop current. Bad news.
Well by the time the longwave trough starts bringing this north there is some cold advection on the western side of the system, which makes the tail appear like a front. The upper cut-off low at this time is pretty dang big on the GFS, a little too big. At this point the system is already going back to baroclinic roots. It does not start that way though.
GFS 180 hours 850mb height/wind/temp:
GFS 180 hours 500mb:
They do not have to be asymmetric. Think of the big winter spirals. They can be symmetric and found in the symmetric warm-core region of the phase diagrams.
If you look at the Gulf Stream Loop......at the North end it would follow that SE turn as the picture shows look at the loop below...
The low appears heavily baroclinic in its initiation despite the cut-off. Still frontal like features.
the eddys look like compact cyclones lol
ok Thanks That will be so Cool.
I'm going to wish I was there with them....
Taco :o)
That is exactly the same as the plot line in Twister!
I don't understand, that basically illustrates what I just pointed out except they also found in the tropical cyclone phase.
We want rain, we want rain, we want rain.
Looking at that there are no frontal characteristics but looking at this the 850mb temps on the western side of the system are cooler than on the eastern side.
The ECMWF also seems to be developing the ridge of more aggressively the GFS. During the 00z and the 06z runs, the GFS was more in consensus with the ECMWF. The 12z GFS is pointing out a different scenario.
See Levi's post 254.
And that diagram proves my point that they can be symmetric.
ok, the genesis of warm seclusion are the same for both phase though. I do not think this will be a warm seclusion.
Here is the "looking ahead" part of the latest San juan NWS discussion, I found it interesting and the last sentance even made me smile :
LOOKING AHEAD...STILL APPEARS THAT BRIEF OVERALL DRYING "MAY"
OCCUR FOR THE SECOND PART OF WEDNESDAY THROUGH EARLY THURSDAY...
BEFORE MOISTURE INCREASES AGAIN LATER THURSDAY THROUGH FRIDAY AND
BEYOND...WITH THE "POTENTIAL" FOR AT LEAST A COUPLE MORE DAYS OF
ACTIVE WEATHER AND "POTENTIAL" HEAVY RAINFALL AND FLOODING...
ESPECIALLY AS WE TRANSITION INTO LATE IN THE WEEK AND THE UPCOMING
WEEKEND. IT IS MAY IN THE NORTHEAST CARIBBEAN. STAY TUNED.
Promising. Things will need to be monitored for possible rain events.
The GFS shows something more frontal in nature moving north and eventually northeast or absorb
The ECMWF shows something much more tropical in nature and a building ridge
In looking at the image you posted and the links to much larger images of the same area posted by PAt (Thanks, Pat!) it sure doesn't look like "sheen", at least not at the SE portion of the plume...
It's not baroclinic when the surface low is stacked directly below the 500mb low.
Most of the cooler 850mb temps in the region are a reflection of the surface temps which are cooler due to cooler SSTs. Earlier maps, such as at 168 hours, show no such appearance of cold advection on the western side:
Afternoon StormW!
Could you discuss what the models are showing with the potential hybrid low?
THis scenerio would be horrible as the flow around the low would push alot of oil towards florida's west coast,this split trough/transition to TD then moving towards the SE coast seems like a feasable solution,IMO
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