Landspout

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A landspout near North Platte, Nebraska on May 22, 2004

A landspout is a slang-term coined by meteorologist Howard Bluestein for a tornado not associated with the mesocyclone of a thunderstorm.^[1] Known officially as "dust-tube tornadoes" by the National Weather Service, they form during the growth stage of convective clouds by the ingestion and tightening of boundary layer vorticity by the cumuliform tower's updraft. Landspouts most often occur in drier areas with high-based storms and considerable low-level instability. They generally are smaller and weaker than supercellular tornadoes, though many persist in excess of 15 minutes and some have produced F3 damage. Their appearance most often is that of a translucent helical tube, similar to waterspouts in appearance and generative mechanisms. They are considered tornadoes because they are an intensely rotating column of air 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.