The June 29 storm that roared out of the western sky and steamrolled across Allen County on a hot Friday afternoon was strange and frightening. We have come to expect violent thunderstorms and even tornadoes in the Midwest. But this was unusual — sudden, vast and destructive.
The term “land hurricane” has been used to describe what occurred. The correct term for the storm is “derecho,” from the Spanish word for “straight.” The term was coined in the late 1880s by a physics professor studying weather phenomena.
A derecho is a warm-weather phenomenon that occurs mostly in the summer, especially during June and July in the Northern Hemisphere. It is a gigantic, unusually powerful, long-lived wind storm that does not rotate like a tornado (also a Spanish derivative) but consists of straight-line winds.
This one blew like a hurricane from Chicago to New Jersey. Some meteorologists report the storm, which killed more than 20 people and left millions without electricity, had five times the energy of normal thunderstorms.
To qualify as a derecho, a storm must cause damage over 240 miles and have wind gusts of at least 58 miles per hour. According to the Washington Post, the June 29 storm not only qualified as a derecho but was “one of the most destructive complexes of thunderstorms in memory.”
Meteorologist Harold Brooks of the National Severe Storm Laboratory in Norman, Okla., confirmed this was one of the most powerful derechos in this part of the country in recent history.
According to meteorologists with the Washington Post, derechos get their power from hot, humid weather. This storm started late Friday morning outside Chicago as a cluster of thunderstorms, says the Weather Channel, and plowed southeast across Indiana, Ohio, Kentucky, West Virginia, Virginia, Maryland, Washington and New Jersey, toppling trees, snapping power poles, downing power lines and ripping roofs off houses.
Derechos typically strike the lower Midwest states once every year, according to the Storm Prevention Center. Across the mid-Atlantic, however, derechos occur only once every four years.
A derecho spawned in Iowa struck Chicago on July 11 last year, leaving more than 860,000 people without electricity. While winds in the Chicago area peaked at about 80 mph, in Iowa they were estimated to be as high as 130 mph, equal to a Category 3 hurricane.
Previously, the most recent significant derecho in the United States occurred on May 8, 2009. That storm moved more than a thousand miles in 24 hours from southeastern Kansas to the southern Appalachian Mountains, leaving several deaths and injuries and millions of dollars of destruction in its wake.
The derecho that tore through Wisconsin and Michigan on May 31, 1998, produced a 128 mph wind gust in Wisconsin. The gusts in Fort Wayne last week reached 91 mph.