Lightning in E Africa Spurs Hurricanes

[latent aaaack]

I thought I was misreading this when I read that lightning is claimed to disturb trade winds the way rocks in a stream create turbulence. I'd never imagined a connection between lightning activity and large scale air movements and really still don't see how that could happen so I wish there was more included in the article.

The link between lightning strikes and hurricane formation should give researchers a heads-up about when a nasty hurricane might form, weeks before it could make landfall in the United States, says Colin Price of Tel Aviv University in Israel. Today, scientists apply various models to predict storm tracks and strength, but only once they form over the Atlantic Ocean. "This is what is unique about our work," Price says. "We look at the initial stages of these devastating storms before they have become hurricanes."

Price and his colleagues at Israel's Open University studied the 2005 and 2006 hurricane seasons, which were markedly different from each other. In 2005 there were a record 28 named storms, including the catastrophic Hurricane Katrina, while 2006 brought only 10 named storms — a 64% reduction. Summertime lightning activity in eastern Africa, mainly in the Ethiopian highlands, was also quite different in each of the years, the researchers found, with 23% less activity in 2006 over 2005.
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http://www.nature.com/news/2007/070508/full/070508-12.html

 

[Myriad]

A weather pattern that causes more severe storms on the mainland results in more lightning. The same type of weather pattern might ultimately result in more hurricanes. That doesn't mean it's the lightning that causes the hurricanes.

By "link between lightning strikes and hurricane formation," the article apparently really means "correlation between the number of lighting strikes and the frequency of hurricane formation." Correlation does not imply causality. Fire trucks are observed at fires with a high degree of statistical significance, but fire trucks don't cause fires.

But it's still an interesting finding. If the results are confirmed in future years (or by evaluating more past years, if the lightning strike data are available), elucidating the phenomena underlying the correlation could be a major advance in hurricane forecasting.

Respectfully,
Myriad

 

[Schneibster]

I would be surprised if it were the lightning itself. The lightning in a thunderhead is a pretty small part of the storm in terms of the energy involved. Thunderstorms are the most powerful individual storm systems. The average thunderstorm dissipates as much energy as a 20kt nuclear warhead- the size of the ones dropped on Hiroshima and Nagasaki- over its several hour lifespan. A large storm can go 10 to 100 times larger; that's 200 kilotons to 2 megatons on the upper end. This energy is dissipated as the thunderstorm progresses. These particular storms are described as intense thunderstorms.

A thunderhead forms when a large bubble of warm, moist air rises high in the atmosphere and cools at the top, then begins to sink, and the warm, moist air keeps coming up. Four conditions are needed to form a thunderhead: heat from the ground, high humidity in the air, a strong temperature gradient to cool the rising bubble of warm, moist air, and something to contain the bubble, like a cold front or some mountains.

Thunderheads (cumulonimbus is the meteorological term for these cloud formations) rise into the stratosphere, and often have their tops stripped off and pushed downwind in the jet stream, from which they get the flat top and "horn" of their characteristic anvil shape. The cooling, and the circulation of the air, produces intense up- and downdrafts in the storm, and can whirl droplets of rain up into the stratosphere, where they freeze, then down to collect more water, and up again, and down again, many times before they become ice balls too heavy to be held up by the air currents and fall as hail. If shear winds form that lay the circulating air currents over sideways, thunderstorms can result in tornadoes; the circular air currents from which the funnel cloud forms are called a "mesocyclone."

Such powerful storms should leave strong turbulence in the atmosphere. This turbulence apparently forms the core of a hurricane as it moves across the Atlantic if conditions are right.

Fascinating. A very interesting find. My compliments.