Smoke in the air could increase the likelihood of tornadoes forming, as well as their intensity.

Pablo Saide of the University of Iowa in Iowa City and his colleagues studied a major tornado outbreak that killed more than 300 people in April 2011 in the southeastern United States. It occurred when smoke particles from fires in Central America drifted across the region, which the team's calculations suggest led to atmospheric changes, such as thicker and lower clouds. These had several cascading effects, including stronger wind shear, that make tornadoes more likely to form and more severe in areas that are prone to such storms.

Meteorologists may need to take smoke into account when forecasting severe weather, the authors say.

Geophys. Res. Lett. http://doi.org/zqq (2015)