Study Reveals Chance Of Extreme Tornado Outbreaks Has Increased

Most death and destruction inflicted by tornadoes in North America occurs during outbreaks—large-scale weather events that can last one to three days and span huge regions. The largest ever recorded happened in 2011. It spawned 363 tornadoes across the United States and Canada, killing more than 350 people and causing $11 billion in damage. Now, a new study shows that the average number of tornadoes in these outbreaks has risen since 1954, and that the chance of extreme outbreaks —tornado factories like the one in 2011—has also increased.