This is Scientific American 60 Second Science.

I'm Christopher in D'Alga. Got a minute?

It's been a light year for tornadoes in the U.S.

Just a few dozens so far. By this time in 2011, a notoriously deadly tornado year,

there had already been more than 120 twisters.

So why the variability?

Well, for decades, scientists have hypothesized that tornado frequency may be related to the

fluctuation of sea surface temperatures in the equatorial Pacific, known as El Nino and

Lagnina.

But the link wasn't clear in the peak springtime tornado season.

Because observations of tornadoes in hail tend to be most prevalent where people can see them,

meaning the data isn't that comprehensive.

So researchers took a step back, looking instead at the basic ingredients of tornadoes and

hail, factors like wind shear, humidity and temperature.

During Leninga, they indeed saw a boost in the conditions that breed springtime twisters and

hail in the southeastern U.S.

In Leningo years, they saw the opposite.

The findings appear in the journal Nature Geo Science.

The study author John Allen, a climatologist at the Earth Institute at Columbia University,

says the data might be used to create yearly tornado

forecasts like this one. So the forecast for this spring is a 60% chance of

being a roundabout normal because we've got a relatively weak El Nino pattern

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