Study: More twisters in biggest outbreaks
Tornadoes coming in clusters like never seen before.
WASHINGTON — The most extreme tornado outbreaks are mysteriously spawning many more t wisters than they did decades ago, a new study concludes.
The once-every-five-yearsor-so outbreak that might have involved 12 tornadoes 50 years ago now has on average about 20, said Columbia University applied physics professor Michael Tippett, lead author of the study published in Thursday’s edition of the journal Science .
The study comes near the end of a year that is on track to have the fewest tornadoes on record, but also on the heels of the outbreak Tuesday night and Wednesday morning that killed five people and injured at least 46 in Alabama and Tennessee — precisely the kind of outbreak Tippett studied.
Tippett and colleagues looked at just the most extreme outbreaks and tornadoes above the minimal wind rating and found a steady uptick in the biggest outbreaks since the mid-1960s.
“Something’s up,” Tippett said. “The tornadoes that do occur are occurring in clusters. It’s not any increase in the (total) number of tornadoes.”
Unlike with other spikes of extreme weather in recent years, Tippett and colleagues could not find the fingerprints of man-made global warming in the change.
Outside experts were split about whether the study made sense.
Some scientists said improved reporting and urban sprawl increases the number of recent tornadoes and negates some of the trend Tippett found. They also disagree with the particular type of measurements he used and some definitions.
“It’s a useful exercise,” said Oklahoma University meteorology professor Howard Bluestein, “but I would be very, very careful in accepting it.”