(NORMAN, Okla.) — Just two years after the worst 12 month period for EF1 or stronger tornados in U.S. history, the country got a big break, as new research from the National Oceanic and Atmospheric Administration shows that last year saw a record low number of severe twisters.
From May 2010 to April 2011, the United States was hit by over 1,000 big tornados, causing more than 535 deaths. The most recent period, from May of last year until this past April, saw only seven tornado fatalities, and less than 200 tornadoes recorded.
According to Harold Brooks, a scientist with the National Severe Storm Lab in Norman, Oklah., it’s “the fewest number of tornado fatalities in a 12 month period since the 19th century.”
Scientists have data about tornados and tornado-related deaths going back to 1954.
Why has the nation been so lucky on this front compared to two years ago? Experts say that a hot summer and a cold winter are factors.
“In the summer-time, when it’s very hot, what we tend to have is the jet-stream is located far north into Canada, and it tends to be very dry at the surface, that’s why we have droughts,” explained Brooks. “When the jet-stream is that far north, the change in the winds with height is weak over the middle part of the country and so none of the ingredients come together to produce the kinds of environments we want to have for tornadoes.”
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