Landspout tornadoes are an atmospheric phenomenon that shares characteristics with destructive tornadoes, yet they originate through a fundamentally different process. These vortices appear as slender, rope-like funnels and can occur with little to no advanced warning, presenting a distinct hazard. Understanding the unique meteorological conditions that create them and their typical intensity is important for accurately assessing the danger they pose compared to their more powerful counterparts.
How Landspouts Form
Landspout tornadoes develop from the ground upward, distinguishing them from tornadoes associated with powerful, rotating thunderstorms. This formation begins when a column of rotating air near the ground, created by converging winds or horizontal wind shear, is stretched vertically by the strong updraft of a developing cumulus cloud directly overhead. As the column is pulled upward into the cloud’s base, the vortex rapidly narrows, causing the rotation to intensify. The resulting structure is a rapidly spinning column of air that connects the surface to the cloud. They are considered non-supercell tornadoes because they do not require a pre-existing rotating updraft, or mesocyclone, within the parent thunderstorm to initiate rotation.
Typical Intensity and Damage Potential
Landspouts are generally less powerful than other types of tornadoes, but they are still capable of causing significant damage and must be treated as a hazard. The majority are rated on the lower end of the Enhanced Fujita (EF) Scale, typically EF0 or EF1. An EF0 rating (65 to 85 miles per hour) is strong enough to snap tree limbs, damage gutters, and remove roof shingles. An EF1 landspout (86 to 110 miles per hour) can cause more substantial damage, capable of overturning mobile homes, pushing cars off roads, and damaging sheds and garages. Although rare, a few landspouts have been documented reaching EF2 intensity, which can tear roofs completely off well-built frame houses.
Structural Differences from Supercell Tornadoes
The primary difference between landspouts and destructive tornadoes lies in the structure of their parent storm. The most intense tornadoes form from supercell thunderstorms, characterized by a deep, persistent, rotating updraft known as a mesocyclone. This rotation originates high in the atmosphere and descends, allowing for long-lived, high-intensity vortices that can reach EF4 or EF5 ratings. Landspouts, by contrast, derive their rotation from the boundary layer near the Earth’s surface and are pulled up by a non-rotating or weakly rotating updraft. The lack of an organized mesocyclone means the landspout is structurally weaker and typically shorter-lived than a supercell tornado.
Taking Action When a Landspout Forms
Any landspout must be taken seriously, as they are capable of causing injury or death. Because they form rapidly without a mesocyclone, landspouts often develop without the clear radar signature that triggers a traditional tornado warning, meaning there is very little lead time. Upon observing a landspout, the immediate action is to seek sturdy shelter, such as a basement, storm cellar, or an interior room on the lowest floor away from windows. Those in mobile homes should evacuate immediately for a pre-identified safe structure, as these residences offer little protection. If caught outdoors or in a vehicle, lie flat in a low-lying area, such as a ditch, protecting the head and neck.