A microburst is a powerful, concentrated downdraft from a cumulonimbus cloud that hits the ground and spreads outward in all directions, producing sudden, extreme wind shifts at the surface. Microbursts are small (less than 4 km diameter) but can generate winds exceeding 270 km/h — comparable to a strong tornado — making them one of aviation's deadliest hazards.
Two types exist: wet microbursts (accompanied by heavy rain or hail, common in humid environments) and dry microbursts (the rain evaporates before reaching the ground, but the cold, dense air still crashes down — common in arid climates). The driving mechanism is evaporative and precipitation-driven cooling: as rain and hail fall through drier air, evaporation cools the air dramatically, making it denser and accelerating its descent. When this cold air column hits the ground, it fans out as a ring vortex with diverging surface winds.
For aircraft, microbursts are extremely dangerous during takeoff and landing: a plane first encounters a headwind (increasing lift), then the downdraft itself, then a sudden tailwind (decreasing lift) — this wind shear sequence has caused multiple fatal crashes. Following landmark research by Dr. Ted Fujita in the 1970s–80s, airports worldwide installed Low-Level Wind Shear Alert Systems (LLWAS) and Terminal Doppler Weather Radars to detect microbursts. On the ground, microbursts can cause localised straight-line wind damage easily mistaken for tornado damage; the key difference is the divergent (outward) wind pattern versus the convergent (inward) pattern of a tornado.