Following are a few of the more historic derechos over the past 2 decades.
May 8, 2009 Super DerechoThis was one of the most intense and unusual derechos ever observed. The wind storm produced significant and often continuous damage over a broad swath from the high plains of western Kansas to the foothills of the Appalachians in eastern Kentucky.
Multiple wind gusts in excess of 70 mph (113 km/h) and a few gusts over 90 mph (145 km/h) were measured along its path. In addition, flash flooding was widespread on the northern edge of the system, especially in Missouri.
But what made the event most unique was the appearance of an unusually strong, long-lived, larger-scale circulation known as a mesoscale convective vortex.
The Mid-South Derecho of 2003
During the early morning of Tuesday, July 22, 2003, a derecho formed over north central Arkansas and moved rapidly east-southeast, reaching northern Alabama by mid-morning.
Although the storm weakened over northern Alabama, it re-developed over northwest Georgia and moved across northern and central Georgia into South Carolina before ending by late afternoon. Many thousands of trees were damaged or blown down. Two people were killed and 11 others were injured, mostly due to trees falling on homes or vehicles.
The "People Chaser" DerechoOn Sunday afternoon, May 27th, 2001, isolated supercell thunderstorms, some producing brief tornadoes, formed over western Kansas. As the outflow of cold air from the supercell storms increased, a gust front developed over southwest Kansas and began moving rapidly southeastward.
The thunderstorms associated with the gust front eventually evolved into a bow echo squall line. The southeast-moving bow echo storm system produced a derecho with significant wind damage over a large part of the southern Plains.
The maximum wind gust in Kansas reached 100 mph (161 km/h) near Garden City. In Oklahoma, a maximum wind gust of 94 mph (151 km/h) was measured at Quail Springs Mall in the northwest part of the Oklahoma City metropolitan area; a gust to 93 mph (150 km/h) was recorded in Ardmore, Oklahoma.
The "Right Turn" Derecho
During the late afternoon of Wednesday, July 12, 1995, thunderstorms formed over southeast Montana and began producing winds that damaged homes and barns and blew over a mobile home. As the storm system moved east across North Dakota, vehicles were overturned and a grain bin was destroyed.
Measured winds reached 70 mph (113 km/h) at Bismarck, ND. As the system approached Fargo, ND during the early morning of July 13th, it became a well-defined bow echo storm with measured winds of 91 mph (146 km/h) at the Fargo airport. Damage was extreme across Minnesota, with over five million trees blown down and many buildings damaged and some destroyed.
The Ontario-Adirondacks DerechoOn the evening of Friday, July 14, 1995, thunderstorms producing severe weather were occurring over Upper Michigan and adjacent portions of Ontario, Canada near Sault Saint Marie.
By late evening the storms had evolved into a bowing line just northwest of the Mackinac Bridge in Michigan. At 10:17 PM EDT, the thunderstorm gust front hit the bridge and a gust to 90 mph (145 km/h) was measured.
Sustained winds above 80 mph (129 km/h) continued on the bridge for 10 more minutes.
The "Storm of the Century" Derecho
On Friday, March 12, 1993, a strong low pressure system formed in the Gulf of Mexico. This low pressure system continued to strengthen dramatically and moved northeast to the mid Atlantic coastal region by Saturday evening, March 13th.
Besides producing a record snowstorm over the eastern United States, this low pressure system was accompanied by an intense squall line with embedded bow echoes ahead of the system's cold front.
"The West Virginia Derecho of 1991"
On the morning of Tuesday, April 9, 1991, a bow echo formed over eastern Arkansas and began to produce wind damage. As the day progressed, a serial derecho developed as the original bow echo raced northeast and expanded in scale, while an additional bow echo formed farther north.
Most of these casualties resulted from falling trees, flying debris, and mobile homes being overturned or destroyed.