Tornado Cluster Sizes Skyrocket

Tornado Cluster Sizes Skyrocket

http://www.livescience.com/57077-extreme-tornado-clusters-are-increasing.html

Tornados are behaving strangely: The number of tornado outbreaks per year is fairly constant, but the number of tornados per outbreak has skyrocketed. And scientists aren't entirely sure why.

In an effort to learn more, researchers looked at meteorological factors related to tornado outbreaks, and then dug into the data to see whether these factors had changed over time, said study lead researcher Michael Tippett, an associate professor of applied physics and applied mathematics at Columbia University.

"The meteorological factors that are related with tornado outbreaks have also become more extreme," Tippett told Live Science in an email. "The surprising finding was that the change in meteorological factors did not have the expected signature of climate change."

That's not to say that climate change isn't involved, he said, but it does leave two possibilities: "Either the recent increases are not due to a warming climate, or a warming climate has implications for tornado activity that we don't understand," Tippett said in a statement.

Tippett said he became interested in tornadoes in the spring of 2011, when multiple deadly twister outbreaks struck the U.S. That includes the multivortex tornado that hit Joplin, Missouri, killing 158 people and injuring more than 1,000.

"The public was asking what caused these record-breaking outbreaks, and scientists didn't have an answer," Tippett said.