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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Looks like normal warming to me.
From this site
Nordic Volcanological Center
Check this out.
I'm watching a Nat Geo special on the Iceland Volcano.
From here.
While you are at it, what will the powerball numbers this weekend? Just a little blog humor.
DRY is not a 4-letter word. But it SHOULD be.
BAH!
May 3
May 8
Activity should begin to pick up once the upward MJO pulse moves in. Maybe around the 23 of May.
Agree.
http://rapidfire.sci.gsfc.nasa.gov/realtime/single.php?2010128/crefl1_143.A2010128114000-2010128114 500.250m.jpg
Tom Brown
MIAMI
Fri May 7, 2010 9:54pm EDTMIAMI (Reuters) - The Gulf of Mexico oil spill may already be bigger than the massive Exxon Valdez spill in 1989 and could have dumped as much as 13 million gallons (49 million liters) of crude into waters off the U.S. coastline, a Florida oceanographer said on Friday.
I'm drinking something stronger than coffee
mine wasn't an accident. hehe
Well, it is May afterall so that's no surprise.
severe risk day 3
Posted: May 7, 2010 10:49 PM
Updated: May 7, 2010 10:50 PM
For the past two weeks, we've heard a variety of solutions for mopping up oil in the Gulf. Everything from hair, to prayer, to that four story dome now hovering above the leak. But a local company says they have the answer, and they've had it waiting for 20 years.
Although it's design and engineering were approved two decades ago, the environmental battleship "Sea Clean" is still just a four foot prototype on the grounds of New Iberia's Schellstede and Associates, Inc.
"It was received very well as far as the concept, however no one would invest the $100-million that it would take to provide that vessel at that time," said Herman Schellstede, President of New Iberia's Schellstede and Associates, Inc.
The price tag has since doubled, but Schellstede says the intent remains the same. Once built, he says "Sea Clean" would be capable of getting to any spill within 18 hours. Giant booms would then fan out to surround the oil spill, then pump the oil onto the vessel, where an onboard recycling facility can process up to 38,000 gallons per minute.
Some have called the prototype the most efficient vessel ever proposed as a solution for deep water blowouts. Schellstede says it's an insurance policy the oil industry ignored once, and can't afford to do so once again.
"I really do believe it's time to try and revisit the Sea Clean."
Jim Hummel
It is from www.katc.com
Satellite imagery supports that the waves continue to emerge off of Africa, but so far they have all been associated (Convection-wise) with the ITCZ. I do not expect any of the waves that are emerging off of Africa to become anything in the next 3-5 days.
In the Atlantic/Caribbean/GOMEX there is pretty much nothing. High shear in the Caribbean due to the TUTT is not allowing development. GOMEX is not favorable for development due to relatively cool SST's. And the Atlantic is being dominated by the TUTT which is increasing dry air/shear.
SPC text- MONDAY STILL HAS THE POTENTIAL TO BE AN ACTIVE WEATHER DAY WITH
STRONG TORNADOES AND VERY LARGE HAIL POSSIBLE...PARTICULARLY OVER
CNTRL/SCNTRL KS AND EXTREME NWRN/NCNTRL OK.
BANDS/CLUSTERS OF ELEVATED TSTMS ARE EXPECTED TO BE ONGOING EARLY
MONDAY ACROSS PORTIONS OF ERN KS/OK OWING TO A ROBUST WAA REGIME
WITHIN A BROAD 45-50 KT SSWLY LLJ. THIS ACTIVITY MAY PROVE
PROBLEMATIC FOR A NWD EXPANSION OF THE WARM SECTOR MONDAY AFTN AND
THIS UNCERTAINTY WAS THE PRIMARY REASON FOR NOT UPGRADING TO A MDT
RISK.
CONFIDENCE REMAINS SUFFICIENTLY HIGH...HOWEVER...IN THE RETURN OF
MID/UPR 60S BOUNDARY LAYER DEW POINTS E OF THE DRYLINE/TRIPLE POINT
INTO AT LEAST SWRN KS BY AFTN. DRYLINE CIRCULATION WILL DEEPEN WITH
APPROACH OF THE UPR TROUGH BY MID-AFTN AND STRONG HEATING WILL ERODE
CINH FOR TSTM INITIATION...MOSTLY LIKELY IN WRN KS. FARTHER
S...CINH WILL BE STRONGER AND LARGE SCALE FORCING COMPARATIVELY
WEAKER ACROSS WRN OK. BUT...ISOLD STORM DEVELOPMENT CANNOT BE RULED
OUT AS FAR S AS WRN OK/RED RIVER.
EFFECTIVE SHEAR IN EXCESS OF 55 KTS AND THE ORIENTATION OF VECTORS
PERPENDICULAR TO THE DRYLINE WILL STRONGLY SUPPORT SUPERCELLS. FCST
HODOGRAPHS EXHIBIT STRONGLY VEERING LOW-LEVEL WINDS WITH THE
COMPLETE VERTICAL PROFILE SIGNATURES INDICATIVE OF HISTORIC STRONG
TORNADIC CASES. VERY LARGE HAIL WILL ALSO BE POSSIBLE.
AS MENTIONED BEFORE...IT IS UNCLEAR HOW FAR N AND E THE QUALITY WARM
SECTOR WILL EXPAND. THE MAXIMUM TORNADO THREAT MAY REALISTICALLY BE
IN NARROW ZONE ACROSS SCNTRL/CNTRL KS INTO NCNTRL OK BEFORE STORMS
MOVE TOWARD A MORE STABLE LOW-LEVEL ENVIRONMENT. LATER OUTLOOKS CAN
ADDRESS THIS UNCERTAINTY.
OTHERWISE...STORMS WILL LIKELY DEVELOP INTO ONE OR MORE MCS/S AND
DEVELOP/MOVE ENE TOWARD THE MID-MS VLY OVERNIGHT WITH LARGE HAIL THE
PRIMARY THREAT.
Current MJO looks pretty frikin' strong to me.
AOI
AOI
AOI
AOI
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