How oil might affect a hurricane
There's no major changes to the forecast for the Gulf of Mexico oil spill. As I discussed in yesterday's post, on Sunday, the winds will begin increasing and shifting to the southeast. The latest run of the GFS model shows that this will be a week-long period of southeast winds, with wind speeds at times reaching 20 - 25 knots. These winds will threaten to bring oil to a large portion of the Louisiana coast, including regions of the central Louisiana coast west of the mouth of the Mississippi River. The Mississippi and Alabama coasts will also be at risk next week, but the risk to the Florida Panhandle is lower. Yesterday's post also has the long-range outlook for oil to get into the Loop Current and spread to the Florida Keys and beyond.
What will oil in the Gulf of Mexico do to a hurricane?
With hurricane season fast approaching and the oil spill in the Gulf of Mexico likely to still be around once hurricane season starts in June, we need to ask, how will oil affect any hurricanes that might traverse over the spill? And how might a hurricane's wind and storm surge affect the spill? Let's consider the first of those questions today.
From the time of the ancient Greeks to the days of the wooden ships and iron men, mariners dumped barrels of oil onto raging seas to calm them during critical moments of violent storms (Wyckoff, 1886.) Oil does indeed calm wind-driven waves, thanks to the reduction in surface tension of the water that oil causes. Ripples with a wavelength shorter than 17 mm are affected by surface tension, and these ripples then cause a feedback that reduces the height of larger waves with longer wavelengths (Scott, 1986.) The reduction of surface tension also impacts the flow of air above the water, and reduces the amount of sea spray thrown into the air, both of which could affect the wind speed. Oil also damps waves by forming a thick, viscous film at the top of the water that resists water motion (Scott, 1999.) Oil also helps calm raging seas by switching off of the wind energy input needed by the wave to break. This occurs because the surface film of oil prevents the generation of ripples on the exposed crests of the waves, and this smoother surface makes the wind less able to grab onto the wave and force it to break.
So, what would happen to a hurricane that encounters a large region of oily waters? A 2005 paper by Barenblatt et al. theorize that spray droplets hurled into the air by a hurricane's violent winds form a layer intermediate between air and sea made up of a cloud of droplets that can be viewed as a "third fluid". The large droplets in the air suppress turbulence in this "third fluid", decrease the frictional drag over the ocean surface, and accelerate the winds. According to this theory of turbulence, oil dumped on the surface of the ocean would reduce the formation of wind-whipped spray droplets, potentially calming the winds. The authors propose spraying oil on the surface of the ocean to reduce the winds of a hurricane. However, the turbulence theory championed by Barenblatt et al. has been challenged by other scientists. In a 2005 interview with Newscientist magazine, turbulence expect Julian Hunt at University College London, UK, remarks, "I am very doubtful about this approach." Hunt studies turbulence both theoretically and in the laboratory, and believes that the high wind speeds in a hurricane are not caused by sea spray. In an article he wrote for the Journal of Fluid Dynamics, Hunt suggests that variations in the turbulence between different regions of the hurricane cause sharp jumps in wind speed, which are responsible for the hurricane's strongest winds.
Oil reduces evaporation
Hurricanes are sustained by the heat liberated when water vapor that has evaporated from warm ocean waters condenses into rain. If one can reduce the amount of water evaporating from the ocean, a decrease in the hurricane's strength will result. Oil on the surface of the ocean will act to limit evaporation, and could potentially decrease the strength of a hurricane. However, if the oil is mixed away from the surface by the strong winds of a hurricane, the oil will have a very limited ability to reduce evaporation. According to a 2005 article in Popular Science magazine, Dr. Kerry Emanuel of MIT performed some tests in 2002 to see if oil on the surface of water could significantly reduce evaporation into a hurricane. He found that the slick quickly dissipated under high wind conditions that generated rough seas.
Figure 1. A comparison of the size of 2008's Hurricane Gustav with the size of the Gulf oil spill. The spill is only about 60 miles in diameter, while a hurricane like Gustav is typically 400+ miles in diameter.
Conclusion
A tropical cyclone in its formative stage--as either a tropical depression or a tropical storm with 40 mph winds--might be adversely affected if it encountered the Gulf of Mexico oil slick, due to the reduction of evaporation into the storm. However, a full-fledged hurricane would mix the oil into the ocean to such a degree that the storm would probably not see any significant reduction in evaporation. It remains unknown how the reduction of sea spray by oil might affect a hurricane. If the oil slick expands to a much larger size, there might be a significant reduction in strength of the hurricane, if theory of how a reduction of sea spray will decrease a hurricane's winds is correct. However, the oil slick is currently Delaware-sized, while a hurricane tends to be Texas-sized, and I doubt that the oil slick at its current size is large enough to have a significant impact on a hurricane's intensity. The slick is about 60 miles across, and it would take a hurricane about four hours to traverse the spill at a typical hurricane forward speed of 15 mph. Furthermore, the slick is within 50 miles land, and interactions with land will dominate the behavior of a hurricane that gets that close to the coast. Unfortunately, there is a decent chance that we'll get a real-world opportunity to see what will happen. June tropical storms tend to form in the Gulf of Mexico, and we've been averaging one June storm every two years since 1995. This year, the odds of a June Gulf of Mexico storm are probably a little lower than usual, shear from our lingering El Niño may bring wind shear levels a bit above average. I expect there is a 20% chance that we'll see a June tropical storm in the Gulf of Mexico that would interact with the oil spill.
References
Barenblatt, G.I, A.J. Chorin, and V.M. Prostokishin, 2005, A note concerning the Lighthill sandwich model of tropical cyclones, PNAS August 9, 2005 vol. 102 no. 32 11148-11150 doi: 10.1073/pnas.0505209102.
Hunt, J.C.R, and I. Eames, 2006, Mechanics of inhomogeneous turbulence and interfacial layers,, Journal of Fluid Dynamics, vol. 554, pp. 499519 doi:10.1017/S002211200600944X.
Scott, J.C., 1986, "The Effect of Organic Films on Water Surface Motions," in Oceanic Whitecaps, edited by E. C. Monohan and G. Mac Niocaill, D. Reidel Publishing Company.
Scott, J.C., 1999, Ocean Surface Slicks - "Pollution, Productivity, Climate and Life-saving", IEEE Proceedings of the International Geoscience and Remote Sensing Symp. IGARSS99, Hamburg, Germany, 28 June-2 July 1999, vol. 3, pp 1463-1468, 1999.
Wyckoff, A.B., 1886, The Use of Oil in Storms at Sea, American Philosophical Society, April 2, 1886.
http://www.archive.org/stream/proceedingsofamep23 amer/proceedingsofamep23amer_djvu.txt
First tropical wave of the season leaves the coast of Africa
Yesterday, the National Hurricane Center noted the first tropical wave of the year coming off the coast of Africa in their Tropical Weather Discussion. The first half of May is the typical time when the first tropical wave comes off the coast of Africa. The wave is currently positioned in the far eastern Atlantic near 5N 45W, and I don't expect it to develop, since it is too close to the Equator to leverage the Earth's spin to gain the rotation needed. The wave has quickly been joined by two new ones today, located at 15W and 36W off the African coast. Tropical waves serve as the seed that form most Atlantic and Eastern Pacific hurricanes.
Portlight delivers major aid shipment to Haiti
Portlight continues to focus its energy and funds on the situation in Haiti, where the rainy season is fast approaching the needs for shelter, medical supplies, food and water remain urgent. Their latest effort was a shipment of several thousand pounds of Durable Medical Equipment and 30,000 pounds of rice that arrived this week via the schooner Halie and Mathew.
Portlight.org is also preparing to respond the the Gulf Coast oil spill by deploying one of more mobile kitchens to feed the hundreds of volunteers likely to flood the coast when the oil finally comes ashore. Please visit the Portlight.org web site or the Portlight blog to learn more and to donate to Portlight's efforts in Haiti and the Gulf Coast.
Figure 2. Relief supplies from the schooner Halie and Mathew sitting at the Portlight Haiti warehouse, ready for distribution.
Next Post
I'm on my way to Tucson today for the American Meteorological Society's 29th Conference on Hurricanes and Tropical Meteorology, which will be held in Tucson next week. My next post will probably be on Monday night, when I plan to discuss the record SSTs observed last month in the tropical Atlantic. I'm excited to be catching up on and blogging about all the latest advancements in hurricane research!
Jeff Masters
Reader Comments
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Watch out for consistency and if the models jump on board then you give it merit. That's no depression, looks more like a strong TS..
Meanwhile, we had one of the wettest dry season's from South to Central Florida. So much so that SFWMD (Water manager's) are concerned about the amount of water in Lake Okeechobee. So as usual they will drain the lake and then we will have a drought.
At 240 hours it is in the Florida straights with a pressure of 1005MB:
At 276 hours it is all the way in the Atlantic:
Very interesting, definitely want to see if it shows the same thing in the 12z and if other models jump aboard.
sst temps run high in sw to nw carb
with increasing temps in gulf now and onward
system most likly will come from sw or nw carb to herald in the start of the season
at the moment
i see the dates may 21 to may 23 as a poss time for first system
after that next chance will be early the first week of june may get two or three early ones just to prime season
then a little quiet till come mid july
then they run till mid sept
with things slowly settling down from there
as we march towards the end of it once again
so as usual, they will drain the lake, wreck the Caloosahatchee and St. Lucie estuaries again, the "then" we will have a drought.
Any reason why they drain it before summer and not after? wont normal evaporation make Lake O drop?
Just to clarify, I am not "downcasting" this hurricane season, in fact, all trends are looking very ominous for the peak season. I am bulking up my roof as well as caulking and painting like mad before the rainy season sets in.
It is just that I do not see the El Nino atmospheric effects going *poof*, even as we head towards what I believe will be neutral-cool conditions before peak season. You have to admit there is a certain amusement factor in seeing some folks "Cape Verde Watching" in early May.
Hey guygee,
The lag of any ENSO event has to do with other conditions going on. For example, if the mean GLAAM state during the transitional period is more on the positive side of things, that may help to suspend "lingering effects." Also, another good question is "where is the forcing?" when you are transitioning to neutral. If the forcing remains in eastern Pacific regions/Dateline etc. then that would tend to bias the pattern toward El Nino.In the case of this summer, I think that the thing that could actually help sustain El Nino like characteristics would be that we don't rapidly switch to a La nina and that the forcing may be focused away from Indonesia. Now, while I do feel there will be decent MJO waves this summer which will transverse all regions, the mean forcing will still have a tendency to be in El Nino regions. On the flip side, the fact that we are in a decadal -PDO/AAM period will certainly help speed up any lag effect, too. So, that to me is a draw and leaves essentially only 1 factor...What will the ENSO state be this autumn
if the lake is high during hurricane season, a storm can then blow out the dike which surrounds the lake causing another 1928 disaster. It "almost" let go during Wilma.
good afternoon Aussie!
I don't see El Nino conditions lingering on as some might suspect might happen. Shear is WAY BELOW average across most of the Atlantic, the Caribbean, GOMEX, and EATL (Storm, if your out there could you please post again the shear climo charts?)
However.. we can all agree on those extreme SSTs, anomalies, and TCHP in the Caribbean especially are record breaking.. all signs point to an average starting season to a rapid build up in August.
Search under models. Hope that helps!
Good Morning indianrivguy. I didn't realize there was a dike around the lake, thought it was just a normal lake like we have here.
One for the bookmarks, thanks for your site 23!
or you will have to get in the back of the truck
papers papers everyone must have papers
Well, I look like a Mexican-American, due to my dark suntan and my heritage (Italian and Cherokee Indian), so I am not going to travel to Arizona anytime soon to be a "victim of racial profiling".
They can pass ALL the laws they want. When you have a corrupt Mexican government, prospering off the back of its citizens, you can build a 100 ft tall wall, people will still get into the USA.
The 30-40 inches of heavy rainfall that will normally occur from June-September in that area can cause the lake to overflow.
It's a hard decision for the Florida officials to make. Do they let the water levels rise, causing a potential flood, or dike failures or do they drop the water levels?
that i can understand, and as i said in reply to indianrivguy , I didn't know there was a dike around the lake, I thought it was a normal lake.
May 2nd
Link
May 9th
Link
A lake here in Australia is normally surrounded but hills or a slight rise in land. no need for dike to hold the water in.
What sort of season with the EPAC CPAC WPAC have this year with neutral conditions?
Oh,..so "Australia Normal".
Thankfully the World is diverse, eh?
I am actually speaking in general terms. Most lakes i have been to are like i described, maybe Lake O is unique.
May 1, 2010
What a difference in the GOMEX huh?
So it's a fresh water dam.
I understand when that happens the Pacific in general turns less active.
EPAC=Average
CPAC=Below Average
WPAC=Average
1928 hurricane
more than 5000 deaths
now the Miami 1926 hurricane also killed some folks in Moorehaven, but the 28 eclipsed it by a lot. This was the costliest of all Atlantic hurricanes.
Amazing what a week of mostly light winds will do. And sunshine, or course.
I hope your right, I'm heading to the Philippines in December for 6 weeks R&R. I would like to see it in 1 piece.
If it had not veered as far north as it did before resuming west, it would have had the effect of filling Lake Pontchartrain, too. Possibly 10 feet higher than normal, or more, maybe. Easily would have flooded a good portion of New Orleans and other areas near the lake.
That storm could have been much worse for the northern gulf coast.
Yes that is because the easterly anomalies (blue) have been prevalent between May 1st and May 6th in the Caribbean. The westerlies (yellow, orange, red) are associated with westerly anomalies which are favorable for reducing the trade winds as observed over the GOM, tropical and subtropical Atlantic.
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