Study: Record-Setting Straight-Line Winds May Be Directly LInked To Warming Climate

On 10 August 2020, a derecho roared through parts of the central United States, covering an area close to 90,000 square miles (240,000 square kilometers) and affecting nearly 20 million people in its path from South Dakota to Ohio. The strongest wind gusts were captured at 140 miles per hour (225 kilometers per hour), with the most destruction reported in central and eastern Iowa and parts of Illinois. With $11 billion in damages, the thunderstorm was the costliest in modern U.S. history.

Putting it into slightly different storm terminology, the 2020 derecho was like a category 4 hurricane in terms of wind speed, said Andreas Prein, a scientist at the National Center for Atmospheric Research. Some scientists suggest that extreme weather may be intensifying as the climate changes. Heavy precipitation increases in a warming atmosphere, but the connection between relatively rare wind events and climate change isn’t yet fully understood. Thunderstorm wind gusts, for instance, are more localized than rainfall from severe storms; this makes the gusts harder to observe or model.

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Standard climate models feature grid spacing of hundreds of kilometers, said Prein, way too large for investigating storms on a smaller scale. In his study, Prein debuted higher-resolution computer modeling, reducing the grid spacing to only 4 kilometers. Prein’s model homed in on 109,387 data points across a map of the U.S. Midwest and revealed how the area affected by strong straight-line winds increased by 4.8% between 1980 and 2022. Prein combined the data gleaned from the high-resolution models and cross-checked them with information recorded at 95 weather stations in the Midwest. The model’s finding largely matched recorded thunderstorm wind gusts (including the 2020 derecho), correlating observations with the model’s output.

“The main innovation of this exciting study is that Prein combines observations and a very high resolution model to extract a clear climate change signal that so far was not known and explains the key physical mechanisms for these changes,” said Erich Fischer, a climate scientist at ETH Zürich who was not involved in the study. Straight-line winds occur when rain evaporates aloft, cooling the air, and then that heavy, cold air rushes down to the ground. By increasing the temperature, which is occurring with climate change, evaporative cooling during a thunderstorm increases as well, Prein said.

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https://eos.org/articles/climate-change-may-be-causing-stronger-thunderstorm-wind-gusts