Landspout

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A landspout near North Platte, Nebraska on May 22, 2004. Note the characteristic smooth, tubular shape, similar to that of a waterspout.

Landspout is a term created by atmospheric scientist Howard B. Bluestein in 1985 for a kind of tornado not associated with a mesocyclone.[1] 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."[2]

Characteristics[edit]

Landspouts are a type of tornado which forms during the growth stage of a cumulus congestus cloud by stretching boundary layer vorticity upward and into the cumulus congestus's updraft. These 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.[3]

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 rapidly 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.

Life cycle[edit]

Forming in relation to miscyclones and under updrafts, a landspout generally lasts for less than 15 minutes; however, they can persist substantially longer, and produce heavy damage. They progress through recognizable stages of formation, maturation and dissipation, and tend to decay when a downdraft or significant precipitation occur nearby. They may form in lines or groups of multiple landspouts.[4]

Damage[edit]

Landspouts are commonly weak; however, in rare occasions, a landspout can be as strong as an EF3 tornado.[4][5]

See also[edit]

References[edit]

  1. ^ Bluestein, Howard B. (1985). "The formation of a "landspout" in a "broken-line" squall line in Oklahoma". Preprints, 14th Conf. on Severe Local Storms, Indianapolis, American Meteorological Society. pp. 267–270. Retrieved 27 March 2007.
  2. ^ American Meteorological Society (2000). "Glossary of Meteorology, Second Edition". ametsoc.org. Retrieved 27 March 2007.
  3. ^ Wakimoto; Wilson (1989). "Non-supercell Tornadoes". Monthly Weather Review. 117: 1113–1140. Bibcode:1989MWRv..117.1113W. doi:10.1175/1520-0493(1989)117<1113:NST>2.0.CO;2.
  4. ^ a b Forbes; Wakimoto (1983). "A Concentrated Outbreak of Tornadoes, Downbursts and Microbursts, and Implications Regarding Vortex Classification". Monthly Weather Review. 111: 220–235. Bibcode:1983MWRv..111..220F. doi:10.1175/1520-0493(1983)111<0220:ACOOTD>2.0.CO;2.
  5. ^ National Weather Service. "EF-0 Landspout Tornado near Grand Junction, MI, on June 30, 2017". Retrieved 20 March 2018.

External links[edit]