When a person thinks of a tornado, they think of a large, rotating cloud stemming from a monster thunderstorm and ripping across the plains of Kansas or Oklahoma. But like so many thing, tornadoes have cousins, similar phenomenon that falls within the technical definition of a tornado, but is formed differently than the typical twisters.
In the high plains, one of these cousins lives. They're called landspouts, and are basically a backwards tornado. They form when areas of circulation on the ground get pulled up from the ground into a storm, thus connecting the ground circulation to the cloud base, making it a tornado.
The term "landspout" is slang for the non-supercell tornado. They typically form when a thunderstorm is in its development stage where the upward motion of the developing cloud is strongest. If there is circulation on the ground beneath this storm associated with a low level boundary, the growing updraft will pull the circulation from the ground up to the cloud. The storm itself often will not have any mesocyclone circulation, thus they are considered non-supercell tornadoes.
Landspouts most often occur in drier areas with high-based storms and considerable low-level instability. They generally are smaller and weaker than supercell tornadoes, though many persist in excess of 15 minutes and some have produced F3/EF-3 damage. They bear an appearance and generative mechanism highly similar to that of waterspouts, usually taking the form of a translucent and highly laminar tube. Visually, the tornado will be wider at the bottom and more narrowed as it reaches higher in the sky. Most often, they are first seen as dust whirls at the ground before finally being pulled into the parent cloud above.
Landspouts are dubbed as "cheap tornadoes" by most great plains chasers since they are often easier to form than supercell tornadoes. They are most typical in Colorado and adjacent points in the high plains and often occur earlier in the day as storms are in their early forming stages. Landspouts are most often found along surface boundaries and wind shifts where the converging winds will create the necessary ground circulation. In these areas, the convergence will force the air at the surface to rise, thus creating thunderstorms. When one of these ground circulations is below this forming storm, it often forms the landspout.
Landspouts occur mostly in the hotter summer months when the heat creates a lot of low level instability. Dust devils are common in these types of conditions and are often seen early in the day on landspout days. The excessive surface heat allows the air to rise better and help with the formation of the landspouts.
Landspouts are often much weaker than typical tornadoes, but have done significant damage in a few instances. More times than not, they'll remain within the EF-0 to EF-1 ratings.
Copyright 2012 Scripps Media, Inc. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.
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