What Is A Derecho?
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A derecho is a widespread, long-lasting wind storm associated with a fast-moving line of severe thunderstorms. To qualify, winds must produce damage along a path at least 250 miles long with gusts of 58+ mph and 75+ mph gusts in at least three places. Derechos can affect millions of people across multiple states.
Derechos are some of the largest and most damaging severe weather events, producing widespread wind damage over hundreds of miles. The name comes from the Spanish word for 'straight' (contrasting with tornado damage from rotating winds). Unlike isolated thunderstorms or tornadoes, a derecho can affect millions of people across multiple states in a single event. Understanding derechos reveals important aspects of how organized thunderstorm complexes behave.
What qualifies as a derecho?
Several criteria define a derecho. The official definition requires: damaging wind gusts (58+ mph) along a path at least 250 miles long, with at least three reports of gusts 75+ mph or higher widely separated, and the damage path showing temporal and spatial continuity from a single weather system. The system must move quickly along its path rather than producing damage in one location. Some definitions add a width requirement (at least 60 miles). The name 'derecho' was coined in 1888 by Gustavus Hinrichs based on Spanish for 'straight,' contrasting with tornado damage.
How does a derecho form?
A derecho forms from a mesoscale convective system (MCS), a large complex of thunderstorms organized into a roughly linear structure. The system develops cold downdrafts that spread outward at ground level, pushing the storm forward like a moving wall. As the storm advances, new thunderstorms continually form along the leading edge, sustaining the system over long distances. The cold pool of dense air at the surface, combined with strong winds aloft, can produce sustained damaging winds across hundreds of miles. The systems often form distinctive bow-shaped patterns on radar.
What damage do derechos cause?
Derechos can cause widespread, severe damage across hundreds of miles. Damage includes downed trees and power lines (often leaving millions without power), structural damage to buildings, vehicle damage from debris, and occasional fatalities. The August 2020 Iowa derecho caused $11 billion in damage, the costliest thunderstorm event in US history, devastating Iowa cornfields and infrastructure. The 2012 Mid-Atlantic derecho left 4 million people without power. Damage along a derecho path can be widespread rather than concentrated like tornadoes, affecting many communities simultaneously.
What are famous historical derechos?
Several notable derechos stand out in recent history. The August 10, 2020 Iowa derecho traveled 770 miles in 14 hours, with winds up to 140 mph, becoming the costliest thunderstorm event in US history. The June 29, 2012 Mid-Atlantic derecho affected 7 states and left 4 million without power during a heat wave, killing 22 people. The May 8, 2009 Super Derecho affected Missouri, Illinois, and Kentucky. Derecho frequency varies by year but the most common areas in the US are the Midwest and southern Great Plains, particularly during summer months.
What qualifies as a derecho?
Several criteria define a derecho. The official definition requires: damaging wind gusts (58+ mph) along a path at least 250 miles long, with at least three reports of gusts 75+ mph or higher widely separated, and the damage path showing temporal and spatial continuity from a single weather system. The system must move quickly along its path rather than producing damage in one location. Some definitions add a width requirement (at least 60 miles). The name 'derecho' was coined in 1888 by Gustavus Hinrichs based on Spanish for 'straight,' contrasting with tornado damage.
How does a derecho form?
A derecho forms from a mesoscale convective system (MCS), a large complex of thunderstorms organized into a roughly linear structure. The system develops cold downdrafts that spread outward at ground level, pushing the storm forward like a moving wall. As the storm advances, new thunderstorms continually form along the leading edge, sustaining the system over long distances. The cold pool of dense air at the surface, combined with strong winds aloft, can produce sustained damaging winds across hundreds of miles. The systems often form distinctive bow-shaped patterns on radar.
What damage do derechos cause?
Derechos can cause widespread, severe damage across hundreds of miles. Damage includes downed trees and power lines (often leaving millions without power), structural damage to buildings, vehicle damage from debris, and occasional fatalities. The August 2020 Iowa derecho caused $11 billion in damage, the costliest thunderstorm event in US history, devastating Iowa cornfields and infrastructure. The 2012 Mid-Atlantic derecho left 4 million people without power. Damage along a derecho path can be widespread rather than concentrated like tornadoes, affecting many communities simultaneously.
What are famous historical derechos?
Several notable derechos stand out in recent history. The August 10, 2020 Iowa derecho traveled 770 miles in 14 hours, with winds up to 140 mph, becoming the costliest thunderstorm event in US history. The June 29, 2012 Mid-Atlantic derecho affected 7 states and left 4 million without power during a heat wave, killing 22 people. The May 8, 2009 Super Derecho affected Missouri, Illinois, and Kentucky. Derecho frequency varies by year but the most common areas in the US are the Midwest and southern Great Plains, particularly during summer months.
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