What is a derecho?
—Mark A. Campbell, Elk Grove Village
A derecho is a family of damaging downburst winds, gushing out of the front of powerful, long-lasting lines of thunderstorms, with speeds that can exceed 100 m.p.h. They usually occur with southeastward-moving squall lines and produce widespread straight-line wind damage across areas hundreds of miles in length. The term derecho, a Spanish word meaning “straight ahead”, was originally coined in the 1880s by Iowa meteorologist Gustavis Hinrichs. These storms generally occur in the summer in a corridor from the northern Plains to the Lower Great Lakes, and if passing through forested areas, can produce catastrophic tree damage known as blowdowns. Derechos usually show up on radar displays as concave- shaped “bow echoes.”