Landspout

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A landspout tornado in the early stages of development by the town of Lamar, Colorado Landspout Tornado near Lamar, CO.jpg
A landspout tornado in the early stages of development by the town of Lamar, Colorado
A landspout tornado forms from a developing thunderstorm near Cheyenne Wells, Colorado. Landspouts are exceptionally common in Eastern Colorado. Landspout Tornado.jpg
A landspout tornado forms from a developing thunderstorm near Cheyenne Wells, Colorado. Landspouts are exceptionally common in Eastern Colorado.
Landspout on September 29, 2007, in Minas Gerais Tornado em Araguari MG 29 set 2007 18 h.JPG
Landspout on September 29, 2007, in Minas Gerais

A landspout is a type tornado not associated with a mesocyclone. [3] The term was coined by atmospheric scientist Howard B. Bluestein in 1985. The Glossary of Meteorology defines a landspout as: [4]

Contents

[A] 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 are typically weaker than mesocyclone-associated tornadoes spawned within supercell thunderstorms, in which the strongest tornadoes form.

Characteristics

Landspouts are a type of tornado that forms during the growth stage of a cumulus congestus or occasionally a cumulonimbus cloud when an updraft stretches boundary layer vorticity upward into a vertical axis and tightens it into a strong vortex. [5] The parent clouds are often predominantly liquid when producing landspouts. [6] Landspouts can also occur due to interactions from outflow boundaries, as they can occasionally cause enhanced convergence and vorticity at the surface. These generally are smaller and weaker than supercell tornadoes and do not form from a mesocyclone or pre-existing rotation in the cloud. Landspouts can form in the flanking line of supercell thunderstorms, following the predominant formation area of landspouts in general within updraft zones without undercutting downdrafts. Because of this lower depth, smaller size, and weaker intensity, landspouts are rarely detected by Doppler weather radar. [5]

Landspouts share a strong resemblance and development process to that of waterspouts, usually taking the form of a translucent and highly laminar helical tube. "They are typically narrow, rope-like condensation funnels that form while the thunderstorm cloud is still growing and there is no rotating updraft", according to the National Weather Service (NWS). [2] 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.

Orography can influence landspout (and even mesocyclone tornado) formation. A notable example is the propensity for landspout occurrence in the Denver Convergence Vorticity Zone (DCVZ).[ citation needed ]

Life cycle

Forming in relation to misocyclones and under updrafts, a landspout generally lasts for less than 15 minutes; however, they can persist substantially longer, and produce significant damage. Landspouts tend to progress through recognizable stages of formation, maturation, and dissipation, and usually decay when a downdraft or significant precipitation (outflow) occur nearby. They may form in lines or groups of multiple landspouts. [7]

Mesocyclone transition

Rarely, a landspout may transitions into a mesocyclonic tornado if the attendant misocyclone merges into a stronger mesocyclone.[ citation needed ]

Damage

Landspouts are usually weak, typically not surpassing the EF0 category. [8] However, on rare ocasions, they have been observed to reach up to EF2 and EF3 intensity. [9] [10]

Examples of such unusually strong landspouts include:

See also

References

  1. ↑ Judson Jones (21 May 2020). "Why Landspout Tornadoes are Common in Colorado". The Denver Post .
  2. 1 2 Judson Jones (8 June 2021). "The No. 1 US county for producing tornadoes just spawned another landspout". CNN .
  3. ↑ Bluestein, Howard B. (1985). "A History of Severe-Storm-Intercept Field Programs". Weather and Forecasting. 14 (4): 267–270. Bibcode:1999WtFor..14..558B. doi: 10.1175/1520-0434(1999)014<0558:AHOSSI>2.0.CO;2 . ISSN   1520-0434.
  4. ↑ American Meteorological Society (2000). "Glossary of Meteorology, Second Edition". ametsoc.org. Archived from the original on 6 April 2007. Retrieved 27 March 2007.
  5. 1 2 Wakimoto; Wilson (1989). "Non-supercell Tornadoes". Monthly Weather Review. 117 (6): 1113–1140. Bibcode:1989MWRv..117.1113W. doi: 10.1175/1520-0493(1989)117<1113:NST>2.0.CO;2 .
  6. ↑ Agee, Ernest; Jones, Erin (1 April 2009). "Proposed Conceptual Taxonomy for Proper Identification and Classification of Tornado Events". Weather and Forecasting. 24 (2): 609–617. Bibcode:2009WtFor..24..609A. doi: 10.1175/2008WAF2222163.1 .
  7. ↑ Forbes; Wakimoto (1983). "A Concentrated Outbreak of Tornadoes, Downbursts and Microbursts, and Implications Regarding Vortex Classification". Monthly Weather Review. 111 (1): 220–235. Bibcode:1983MWRv..111..220F. doi: 10.1175/1520-0493(1983)111<0220:ACOOTD>2.0.CO;2 .
  8. ↑ "Tornado Facts" . Retrieved August 9, 2024.
  9. ↑ "Storm Spotter Field Guide: Non-supercell Tornadoes" . Retrieved September 2, 2025.
  10. 1 2 "Landspout Tornadoes continued..." (PDF). The Dryline — The Official Newsletter of the National Weather Service in Amarillo. José Garcia. Summer 2014. p. 3. Retrieved September 2, 2025.
  11. ↑ "June 7th, 2021 Weld County Tornado" . Retrieved September 2, 2025.
  12. ↑ "Storm Events Database June 7, 2021" (Report). National Centers for Environmental Information. National Centers for Environmental Information. Retrieved September 2, 2025.
  13. ↑ "European Severe Weather Database". European Severe Storms Laboratory. Retrieved September 2, 2025.
  14. ↑ "Tornado Archive". tornadoarchive.com. Retrieved September 2, 2025.
  15. ↑ James F.W. Purdom; John F. Weaver (October 1990). "A Satellite Perspective of the June 15, 1988 Tornado Outbreak in Denver, Colorado" (PDF). American Meteorological Society. Archived from the original (PDF) on March 7, 2022. Retrieved September 2, 2025.
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