A derecho is a rare but extremely powerful straight-line windstorm that moves rapidly across a large area, often leaving destruction similar to a tornado — but without the rotation. The word “derecho” comes from Spanish, meaning “straight,” which reflects the storm’s forward movement and the direct path of its damaging winds.
Derechos typically form during warm-weather months and can stretch for hundreds of kilometers, affecting multiple regions within hours. They’re most common in North America, especially the central U.S., but have also been recorded in parts of Europe and South America.
How a Derecho Forms
Derechos are born from large, organized thunderstorm systems called mesoscale convective systems (MCS). When conditions in the atmosphere are right — including high heat, humidity, and wind shear — these systems can evolve into fast-moving walls of storms that bow outward on weather radar, known as a “bow echo.”
This bow shape is where the strongest winds occur. Gusts in a derecho can exceed 160 km/h (100 mph), powerful enough to knock down trees, destroy buildings, and flip vehicles.
How Is a Derecho Different from a Tornado?
- Winds in a tornado rotate, while derecho winds blow in one direction (straight-line).
- Derechos affect much larger areas, sometimes stretching over 400 km.
- Tornadoes usually hit small, concentrated zones, while derechos spread damage over wide paths.
Though less dramatic-looking than tornadoes, derechos can cause more widespread damage due to their size and duration.
Effects and Dangers
Derechos can lead to:
- Massive power outages due to fallen trees and power lines
- Widespread crop destruction, especially in farming regions
- Flash floods, as heavy rain often accompanies them
- Structural damage similar to that caused by hurricanes
In urban areas, falling debris, broken glass, and collapsed buildings can pose serious safety risks to people outdoors or in weak structures.
How to Stay Safe
- Stay informed: Watch weather alerts during hot, humid periods when severe thunderstorms are likely.
- Take shelter: If a derecho is approaching, move indoors, away from windows, and stay low.
- Prepare for outages: Have backup power, water, and supplies ready in storm-prone regions.
- Avoid travel: High winds can topple vehicles and make driving extremely dangerous.
Glossary
- Derecho – A widespread, long-lived straight-line windstorm associated with fast-moving thunderstorms.
- Straight-line wind – Wind that moves in a single direction, unlike rotating tornado winds.
- Bow echo – A curved radar pattern indicating strong wind-producing storms.
- Mesoscale convective system (MCS) – A large cluster of thunderstorms working together as one powerful system.
- Wind shear – A difference in wind speed or direction with height, often triggering severe storms.
