Could El Niño quash tornadoes?

Doyle Rice
A large tornado forms under an enormous supercell near El Reno, Okla., in 2011.

Scientists know that El Niño tends to subdue Atlantic hurricanes, and a new study says it could do the same to spring tornadoes across the South.

"We can forecast how active the spring tornado season will be based on the state of El Niño or La Niña in December or even earlier," said John Allen, a Columbia University research scientist and lead author of the study.

El Niño and La Niña are natural climate patterns in which sea-surface temperatures in the central Pacific Ocean fluctuate between warm and cool. When the water is warmer than average, as it is now, it is described as El Niño. When cooler, it is La Niña.

The overall pattern is among the biggest influences on weather and climate in the U.S. and around the world.

The study found that a fairly strong La Niña brings more tornadoes and hailstorms over portions of Oklahoma, Texas, Kansas and other parts of the southern United States. El Niños act in the opposite manner, suppressing both types of storms in this region.

Allen said this seasonal forecast information would allow governments and insurance companies to prepare for a upcoming tornado season.

The deadly 2011 tornado season —- which occurred during a La Niña — saw at least 550 Americans killed and several billion dollars in damages.

This year, the U.S. is officially in an El Niño, and tornado activity has been noticeably quieter than average. Allen and his colleagues, in an experimental forecast for this spring, said there will be a somewhat lower tornado risk because of the current El Niño.

While previous studies have shown some links between El Niño and winter tornado activity, this is the first one that ties El Niño to the active tornado season in the spring.

AccuWeather meteorologist Mike Smith, who was not involved in the study, likes the study but notes that El Niños can't really be accurately predicted months in advance. He pointed out that El Niño was forecast to form last year but never really did.

He also said that "the author's methodology does not actually compare against actual tornadoes but rather tornado conditions," which are only loosely correlated to tornadoes.

The study authors said they didn't use actual tornado data because of inaccurate or incomplete record-keeping over the past few decades.

The study was published online Monday in the British journal Nature Geoscience.

During an El Niño phase, (top), the frequency of tornadoes goes down. During a La Niña phase (bottom), tornadoes increase (indicated by red areas). The effect is strongest in the boxed area.