The National Weather Service in Des Moines says on this day (Aug 23) in 2011, a rare phenomena known as a heat burst affected portions of southwest Iowa. A heat burst is characterized by a sudden rise in temperature, a drop in humidity, and strong winds that can approach or exceed severe levels. They are associated with high based, decaying thunderstorms with a substantial dry layer beneath the base of the storm. As rain from the thunderstorm falls into the underlying dry air, it cools the air immediately around it, which becomes denser than the surrounding air and begins to sink.

As this air sinks, it dries out and compresses adiabatically (a type of thermodynamic process that occurs without transferring heat or mass between the thermodynamic system and its environment), which results in the hot and dry readings recorded with heat bursts.

This event produced damage in Adair and Audubon Counties.  Atlantic’s temperature rose from 84 degrees at 6pm to 102 by 7:25-pm!