How Do Windstorms Form?

windstorms-form Credit: vinothchandar/CC-BY-2.0

Windstorms, also known as derecho winds, are produced by what meteorologists call downbursts. A downburst is a ground-level wind system in which gusts may blow in all directions from a single source. Most windstorms are made up of several downburst clusters, which in turn are composed of smaller bursts.

The downdrafts that make up downbursts are typically formed when the air is cooled by the evaporation of moisture from thunderstorms or other convective clouds. The cooled air becomes denser than the surrounding environment, and it speeds downward. Windstorms develop when weather conditions are right for the repeated development of such systems in the same area. Such clusters of downbursts may spread for up to 50 to 60 miles and persist for half an hour or more. Within the individual downbursts, there also may develop even more intense winds known as microbursts, which can spread over two miles and be very dangerous for nearby aircraft. Within the microbursts, even more powerful winds that are as destructive as tornadoes may develop; these are known as burst swaths.

A windstorm may or may not be accompanied by precipitation from the source thunderstorm. Wind speeds usually exceed 34 miles per hour and can cause considerable damage.