gustnadoes

Gustnadoes are small, ground-based vortices that resemble tornadoes but form along a gust front or other outflow boundary, such as a squall line, rather than from a storm’s main updraft. They occur most often with non-supercell thunderstorms when the outward-moving air creates strong shear and shallow rotation that can be tilted into the vertical and reach the ground.

Formation of a gustnado typically involves wind shear near a convective outflow and the creation of horizontal vorticity. As the gust front propagates, nearby wind shear and turbulence can tilt this vorticity into a vertical orientation, producing a brief, ground-contacting vortex along the boundary. The resulting feature is usually short-lived and confined to a narrow path.

Characteristics and distinction from tornadoes are practical in evaluation. Gustnadoes are generally small, short-lived, and weaker than most tornadoes, though they can still cause localized damage, especially to trees, mobile structures, or unsecured objects. They are often associated with non-tent-pole thunderstorm activity and can lack the strong, persistent rotation typical of tornadoes produced by mesocyclones. Radar signatures, if present, tend to be weak or ambiguous, and gustnadoes may be difficult to detect before they occur.

Safety considerations emphasize treating any observed rotating dust, debris, or condensation along an outflow boundary as potentially dangerous. If a gust front or visible rotation is encountered, seek shelter in a sturdy interior room on the lowest available floor and protect yourself from debris. See also tornado; funnel cloud; downburst.