Derecho
Derechos are fast-moving bands of thunderstorms with destructive winds. The winds can be as strong as those found in hurricanes or even tornadoes. Unlike hurricanes and tornadoes, these winds follow straight lines (NOAA, 2019).
Primary reference(s)
NOAA, 2019. What is a Derecho? National Oceanic and Atmospheric Administration (NOAA). Accessed 16 May 2025.
Annotations
Additional scientific description
A derecho (pronounced similar to 'deh-REY-cho') is a widespread, long-lived wind storm that is associated with a band of rapidly moving showers or thunderstorms. Although a derecho can produce destruction similar to the strength of tornadoes, the damage is typically directed in one direction along a relatively straight swath. As a result, the term 'straight-line wind damage' is sometimes used to describe derecho damage. By definition, if the wind damage swath extends more than 240 miles (about 400 km) and includes wind gusts of at least 58 mph (93 km/h) or greater along most of its length, then the event may be classified as a derecho (NOAA, 2019).
A derecho is a widespread convectively induced straight-line windstorm. Specifically, the term is defined as any family of particularly damaging downburst clusters produced by a mesoscale convective system (AMS, 2012a). Such systems have sustained bow echoes with book-end vortices and/or rear-inflow jets and can generate considerable damage from straight-line winds. Damage must be incurred either continuously or intermittently over a swath of at least 650 km (~400 miles) and a width of approximately 100 km (~60 miles) or more. The term derecho derives from a Spanish word that can be interpreted as 'straight ahead' or 'direct' and was chosen to distinguish between wind damage caused by tornadoes (AMS, 2012b), which have rotating flow, from straight-line winds.
The National Oceanic and Atmospheric Administration Storm Prediction Center reports that the types of derecho include: serial derechos, progressive derechos, hybrid derechos and low-point derechos (NOAA, 2018).
Metrics and numeric limits
The winds associated with derechos are not constant and may vary considerably along the derecho path, sometimes being below severe limits (57 mph [92 km/h] or less) and sometimes being very strong (from 75 mph [121 kph] to over 100 mph [161 kph]). This is because the swaths of stronger winds within the general path of a derecho are produced by what are called downbursts, and downbursts often occur in irregularly arranged clusters, along with embedded microbursts and burst swaths. Derechos might be said to be made up of families of downburst clusters that extend, by definition, continuously or nearly continuously for at least 250 miles (about 400 km) (NOAA, 2018).
Key relevant UN convention / multilateral treaty
Sendai Framework for Disaster Risk Reduction 2015-2030.
Drivers
Derechos are formed as follows. When the wet air in a thunderstorm meets the drier air surrounding it, the water in the air evaporates. When water evaporates, it cools the air around it. Since the cool air is denser, it rapidly sinks to the ground and creates strong winds. The downburst can suck more dry air into the storm, making even stronger downbursts or clusters of downbursts. Derechos occur when the right conditions for downbursts occur over a wide area (NOAA, 2019). See also NOAA (2018) for more detailed information about derechos.
Impacts
Because derechos are most common in the warm season, those involved in outdoor activities are especially at risk. Campers or hikers in forested areas are vulnerable to being injured or killed by falling trees, and those at sea risk injury or drowning from storm winds and high waves that can overturn boats. Another reason people outdoors are especially vulnerable to derechos is the rapid movement of the parent convective system. Typically, derecho-producing storm systems move at speeds of 50 mph or more, and a few have been recorded at 70 mph. For someone caught outside, such rapid movement means that darkening skies and other visual cues that serve to identify the impending danger (e.g., gust front shelf clouds) appear at very short notice (NOAA, 2018).
Multi-hazard context
The figure below summarises common interactions between derechos and other hazards. This information should be used with caution and not be solely relied upon in Disaster Risk Management, particularly as some interactions may not have been included. Note that hazardous events occurring together or locally in space or time may not necessarily cause, amplify, or be otherwise related to each other. Specific examples of multi-hazard context can be found in the ‘Hazard drivers’ and ‘Impacts’ sections above.
Multi-hazard diagram
Risk Management
No Information Available
Monitoring
The section above and the table below offer an overview of monitoring derechos. This information can be used for forecasting within a national early warning system (EWS). Since EWS capacities and processes differ across countries, the most current and specific information regarding EWS should be obtained from the appropriate national or regional agency/authority responsible for disaster management.
| Which institution(s) produce(s) Disaster Risk Data/Information? |
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| How is the Hazard Observed/Monitored/Forecast? | Derechos are monitored using Doppler radar, weather satellites, and ground-based sensors that track cloud structures, wind patterns, and lightning activity. Meteorologists analyse key atmospheric conditions, including temperature, humidity, and wind shear, to assess the potential development and intensity of these widespread, fast-moving storms. By integrating advanced numerical weather models with real-time observational data, forecasters improve the accuracy of derecho predictions and track their movement. This enables timely warnings to mitigate risks to aviation, infrastructure, and communities from associated hazards such as damaging straight-line winds, heavy rainfall, lightning, and hail. |
References
American Meteorological Society (AMS), 2012a. Glossary of Meteorology: Mesoscale Convective System. American Meteorological Society (AMS). Accessed 16 May 2025.
American Meteorological Society (AMS), 2012b. Glossary of Meteorology: Tornado. American Meteorological Society (AMS). Accessed 16 May 2025.
American Meteorological Society (AMS), 2019. Glossary of Meteorology: Derecho. American Meteorological Society (AMS). Accessed 16 May 2025.
National Oceanic and Atmospheric Administration (NOAA), 2018 About Derechos. Storm Prediction Center, National Oceanic and Atmospheric Administration (NOAA). Accessed 16 May 2025.
National Oceanic and Atmospheric Administration (NOAA), 2019. Derecho. National Weather Service, National Oceanic and Atmospheric Administration (NOAA). Accessed 16 May 2025.