downbursts

Downbursts are powerful downdrafts within thunderstorms that strike the ground and spread out in all directions, producing damaging straight‑line winds. They can occur suddenly and are a major cause of wind damage during severe weather. Downbursts vary in size and intensity and are commonly categorized as microbursts, which are small in scale, and macrobursts, which cover larger areas. They can be wet, with visible rainfall reaching the surface, or dry, with little or no rain at ground level.

Formation and structure: A downburst forms when air within a thunderstorm becomes negatively buoyant and accelerates downward due to gravity, often aided by cooling from evaporating rain and aerodynamic drag. As the descending air nears the surface, it diverges outward, creating a gust front that can lift or topple objects and generate damaging winds over a relatively short distance (microbursts) or a broader area (macrobursts).

Detection and hazards: Doppler radar can detect strong downdrafts and the associated outflow boundaries, while surface observations record abrupt, powerful wind gusts. Downbursts pose a particular risk to aviation during takeoff and landing, when aircraft operate at low altitude and near the storm’s outflow. They can occur with a single storm or as part of a line of storms that produces a derecho, a long-lasting corridor of damaging winds.

See also: gust front, derecho, straight‑line winds, tornado.