A landspout is a term coined by meteorologist Howard B. Bluestein in 1985 for a kind of tornado not associated with a mesocyclone. The Glossary of Meteorology defines a landspout as
- "Colloquial expression describing tornadoes occurring with a parent cloud in its growth stage and with its vorticity originating in the boundary layer.
- The parent cloud does not contain a preexisting mid-level mesocyclone. The landspout was so named because it looks like "a weak Florida Keys waterspout over land."
Landspouts form during the growth stage of a cumulus congestus cloud by stretching boundary layer vorticity upward and into the cumulus congestus's updraft. They generally are smaller and weaker than supercell tornadoes and do not form from a mesocyclone or pre-existing rotation in the cloud. Because of this, landspouts are rarely detected by Doppler weather radar.
Landspouts share a strong resemblance and development process to that of waterspouts, usually taking the form of a translucent and highly laminar helical tube. Landspouts are considered tornadoes since a rotating column of air is in contact with both the surface and a cumuliform cloud. Not all landspouts are visible, and many are first sighted as debris swirling at the surface before eventually filling in with condensation and dust.
A few landspouts can persist in excess of 15 minutes and have produced F3 damage; however, they are most commonly weak, with winds under 85 miles per hour and causing little damage.