The Ohio State University's Associate Professor Jana Houser from the Department of Geography recently authored a piece in The Conversation explaining how a decaying El Niño contributed to a series of tornadoes that struck the central United States from April 26-28, 2024. These tornadoes caused extensive damage from Oklahoma to Nebraska and Iowa and were unusual for the time of year, occurring further north and east than typical late April tornado activity, which usually centers in Oklahoma and Texas.

These tornadoes coincided with the atmospheric transition out of El Niño, a cyclical climate phenomenon affecting both the oceans and the atmosphere. As El Niño decays, atmospheric waves become more pronounced, enhancing the conditions necessary for tornado formation.

Tornadoes require two primary conditions: warm, moist surface air and cold air above, along with vertical wind shear—where wind speed and direction change with altitude. In late April, warm, humid air from the Gulf of Mexico was transported northward by surface low-pressure systems, while cold air was carried through the middle atmosphere by Rossby waves. These waves also enhanced vertical wind shear, creating a prime environment for tornadoes.

On April 26, a small atmospheric wave triggered tornadoes in Nebraska and Iowa, including a large tornado in Omaha and Minden. A larger wave moved through Oklahoma the following day, causing tornadoes in several small towns.

The decay of El Niño has a profound impact on atmospheric waves, significantly increasing their amplitude. This amplification tends to enhance tornado conditions, leading to a higher likelihood of tornado outbreaks. The strong El Niño of 2023-24, which weakened in April 2024, was a contributing factor to the storm outbreak.

Early warnings and improved forecasting models likely saved lives by alerting the public to the severe weather days in advance. The accuracy of predicting tornado conditions has significantly improved with the advent of high-resolution weather models, enabling more precise warnings and better preparedness.

Visit Ohio State News to read "What a decaying El Niño has to do with tornadoes in the central US."

Professor Houser was recently awarded the Martha L. Corry Faculty Fellow by Ohio State's Department of Geography. Professor Bryan Mark, the former State Climatologist of Ohio, was one of the most recent awardees of this prestigious appointment. Visit the geography department's site to learn more.