Derechos “are primarily a summer phenomenon,” said Harold Brooks, senior researcher at the National Severe Storms Laboratory of the National Oceanic and Atmospheric Administration. “If you make it more summery, you can expect them to increase.”
“What makes derechos painful is that although their winds are often not strong enough to destroy buildings, they destroy power lines and trees over a large area,” added Dr Brooks. “Tornado paths can have intense destruction in the middle. In a derecho, it covers a much larger area.
The threatening weather of the week shocked even professional weather observers. Zach Sharpe, who runs the Iowa Storm Chasing Network, said he had never experienced such bizarre weather in December.
Much of Wednesday was unusually warm for the season – “It was like spring; there were people wearing shorts, ”he said – but once the storm front approached, a blast of cold air instantly brought freezing temperatures and winds of 80 miles on time. “It was strange chasing tornadoes 10 days before Christmas,” Sharpe said. “We were in our vehicles, listening to Jingle Bells, as the tornado sirens went off. “
Yet, scientists said, this week’s storm was so unusual and had so many different forces behind it, including a strong jet stream moving through central states, that it can be difficult to disentangle the impact. of global warming compared to other factors such as La Niña. , an intermittent climatic phenomenon in the Pacific Ocean that can influence winter storms.
This storm was “about as messy an event as it gets,” Dr Brooks said. “Is this a weird one-off event? Or maybe it won’t repeat itself for long? Will the seasonality change a lot? I don’t think we know that.
Victor Gensini, professor of meteorology at Northern Illinois University, pointed out that all extreme weather events now take place against the backdrop of an atmosphere that has been deeply shaped by humans burning fossil fuels. “Suppose all extreme weather events are affected by climate change,” he said.