Odd weather pattern baffles experts: US lately lurches from lots of tornadoes to unusual quiet

 

http://www.foxnews.com/us/2014/04/30/odd-weather-pattern-baffles-experts-us-lately-lurches-from-lots-tornadoes-to/

Tornadoes can occur any time of year. All it takes is the right conditions. It varies by location, but the season tends to run from spring to mid-summer, with the biggest hotspots in Texas, Kansas, Oklahoma, Florida and Nebraska.
In the past few decades, the U.S. has averaged annually about 1,250 tornadoes of all sizes. Longer trends also show more tornado clusters recently. The number of days with at least one significant tornado is going down.
In the early 1970s, there was a single tornado about 150 days a year. Now it's about 100, said Harold Brooks, a meteorologist at the National Severe Storms Lab in Norman.
But the number of super-busy days with 30 tornadoes or more has gone up. In the 1970s, they came once every two years or so. Now we get those days three times a year, Brooks said.