Without Thunderstorms, the Number of Twisters Plunges; Storm Chasers Lament
The unusual weather patterns that have caused heat waves, droughts and wildfires this summer also have brought some good news: a record low number of tornadoes.
Since mid-April, about 300 tornadoes have hit the U.S., the fewest in that span in nearly 60 years of record-keeping and about one-third the average tally for the period, according to the National Oceanic and Atmospheric Administration. While the hot, dry weather has killed dozens of people and ruined crops this summer, it also has prevented major tornado outbreaks.
“This is a really rare event,” said Harold Brooks, a research meteorologist at NOAA’s National Severe Storms Laboratory. “The simple reason is: You aren’t going to get a tornado if you don’t have thunderstorms.”
Tornadoes form in severe storms that are caused by two clashing weather systems. This year, a high-pressure system has hovered over the middle of the U.S., creating oppressive heat and little precipitation—unfavorable conditions for tornadoes. The system also has kept the jet stream north, which means the high-altitude winds necessary for tornadoes are remaining in Canada and not the U.S.