Macroburst

A macroburst is a meteorological term for a powerful downburst associated with a thunderstorm that produces damaging winds over a large area. It is defined as a downburst with a horizontal extent greater than about 4 kilometers (2.5 miles) at the surface. The event is characterized by an intense downdraft that transports air from aloft to the ground, where the air then spreads outward in all directions, generating a strong gust front.

Mechanism and structure: The downdraft forms as precipitation and evaporative cooling drive air downward inside the thunderstorm. When this air reaches the surface, it radiates outward, creating a broad, straight-line wind field. Macrobursts are often linked to organized convective systems such as squall lines or bow echoes and can be a component of derechos, though they may also occur in isolated storms.

Size, duration, and wind speeds: The damage path of a macroburst can extend for tens of kilometers along the storm’s track, with the peak winds commonly exceeding 100 mph and sometimes reaching higher values in extreme cases. The strongest surface winds are typically confined to a relatively brief period at a given location, lasting only a few minutes.

Impacts and detection: Macrobursts cause widespread, straight-line damage, which can resemble tornado damage but lacks rotational features. They pose significant hazards to aircraft during approach and departure. On weather radar, macrobursts may appear as bowing storm segments and strong outflow signatures, often with accompanying high reflectivity and jet outflow.

See also: Downburst, Microburst, Derecho, Bow echo, Gust front, Thunderstorm.