What is a Gustnado?
A gustnado is a small, short-lived column of rotating air that forms along a thunderstorm’s outflow boundary, known as a gust front. Unlike a true tornado, it does not connect to the cloud base and is not driven by a mesocyclone. Instead, a gustnado is a surface-based circulation, formed by strong wind shear at the ground where cooler, outflowing air from a thunderstorm interacts with warmer, stationary air.
Visually, a gustnado often appears as a swirling dust whirl or debris swirl near the ground, sometimes extending a short distance vertically. Its formation is directly tied to the leading edge of a thunderstorm’s downdraft, where winds rapidly change direction and speed. This localized rotation is transient, lasting only a few minutes or less.
How Dangerous Are Gustnadoes?
While gustnadoes are generally weaker and shorter-lived than tornadoes, they can still present a localized threat. The wind speeds within a gustnado can be significant, often equivalent to those found in weak tornadoes or strong straight-line winds. These speeds frequently fall within the range of 65 to 110 miles per hour, corresponding to the EF0 or EF1 categories on the Enhanced Fujita Scale.
Such wind speeds are sufficient to cause notable damage to property and vegetation. Gustnadoes have been observed overturning mobile homes, snapping tree limbs, and damaging sheds. Although their path of destruction is narrow and brief, the localized intensity means they pose a real, albeit constrained, risk to life and property within their immediate vicinity.
Distinguishing Gustnadoes from Tornadoes
A key distinction between a gustnado and a true tornado lies in their connection to the parent thunderstorm. A tornado forms from a rotating updraft within the storm, known as a mesocyclone, and maintains a continuous circulation from the ground up to the cloud base. In contrast, a gustnado is a ground-based circulation not directly connected to the main storm updraft or the cloud base.
Visual cues help differentiate these phenomena. Tornadoes typically exhibit a visible condensation funnel extending downward from the cloud, whereas gustnadoes usually appear as a swirling column of dust or debris at the surface without a clear connection to the overhead cloud. Furthermore, tornadoes can persist for much longer durations, sometimes tens of minutes or more, while gustnadoes are short-lived, often dissipating within a minute or two.
What to Do if You See a Gustnado
Upon observing any rotating column of air, treat it as potentially dangerous. The most immediate safety measure is to seek sturdy shelter. If you are outdoors, move indoors immediately and find a safe spot away from windows.
Once inside, move to the lowest level of the building, such as a basement, or an interior room on the ground floor. Staying informed through official weather alerts from local authorities or weather services is important during severe weather events.