Tornado outbreaks – mega-storms in which a cluster of six or more tornadoes occur in close succession – are responsible for nearly 80 percent of tornado-related fatalities in the US. And the worst part is, these deadly chains of twisters have been getting even more intense in recent years.
Earlier in the year, researchers led by Columbia University found that the average number of tornadoes making up these outbreaks had risen since the 1950s, increasing from about 10 per year back then to about 15 per year now.
But new research published by the same team has found that something even scarier is going on.
Looking at records from the last 50 years, the researchers found that the frequency of US outbreaks with multiple tornadoes is increasing – and is rising faster for the most extreme outbreaks.
In the worst of these storms, outbreaks can contain dozens of individual twisters that collectively wreak havoc over a large region for days at a time.
Between 1965 and 2015, the researchers identified 435 of these extreme events, and during that timeframe, the membership in these mega-storms effectively doubled, from an estimated 40 twisters per outbreak in 1965 to nearly 80 in 2015…