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Landspout is a term created by atmospheric scientist Howard B. Bluestein in 1985 for a kind of

tornado A tornado is a violently rotating column of air that is in contact with both the surface of the Earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud. It is often referred to as a twister, whirlwind or cyclone, altho ...

not associated with a

mesocyclone A mesocyclone is a meso-gamma mesoscale (or storm scale) region of rotation (vortex), typically around in diameter, most often noticed on radar within thunderstorms. In the northern hemisphere it is usually located in the right rear flank (back ...

. The ''Glossary of Meteorology'' defines a landspout as : "Colloquial expression describing tornadoes occurring with a parent

cloud In meteorology, a cloud is an aerosol consisting of a visible mass of miniature liquid droplets, frozen crystals, or other particles suspended in the atmosphere of a planetary body or similar space. Water or various other chemicals may co ...

in its growth stage and with its

vorticity In continuum mechanics, vorticity is a pseudovector field that describes the local spinning motion of a continuum near some point (the tendency of something to rotate), as would be seen by an observer located at that point and traveling along wit ...

originating in the

boundary layer In physics and fluid mechanics, a boundary layer is the thin layer of fluid in the immediate vicinity of a bounding surface formed by the fluid flowing along the surface. The fluid's interaction with the wall induces a no-slip boundary condi ...

. : The parent cloud does not contain a preexisting mid-level mesocyclone. The landspout was so named because it looks like "a weak

Florida Keys The Florida Keys are a coral cay archipelago located off the southern coast of Florida, forming the southernmost part of the continental United States. They begin at the southeastern coast of the Florida peninsula, about south of Miami, and e ...

waterspout A waterspout is an intense columnar vortex (usually appearing as a funnel cloud, funnel-shaped cloud) that occurs over a body of water. Some are connected to a cumulus congestus cloud, some to a cumuliform cloud and some to a cumulonimbus clou ...

over land." Landspouts are typically weaker than mesocyclone associated tornadoes spawned within

supercell A supercell is a thunderstorm characterized by the presence of a mesocyclone: a deep, persistently rotating updraft. Due to this, these storms are sometimes referred to as rotating thunderstorms. Of the four classifications of thunderstorms (s ...

thunderstorms, in which the strongest tornadoes form.

Characteristics

Landspouts are a type of tornado that forms during the growth stage of a

cumulus congestus Cumulus congestus clouds, also known as towering cumulus, are a form of cumulus that can be based in the low or middle height ranges. They achieve considerable vertical development in areas of deep, moist convection. They are an intermediate stage ...

or occasionally a

cumulonimbus Cumulonimbus (from Latin ''cumulus'', "heaped" and ''nimbus'', "rainstorm") is a dense, towering vertical cloud, typically forming from water vapor condensing in the lower troposphere that builds upward carried by powerful Buoyancy, buoyant air ...

cloud when an

updraft In meteorology, an updraft is a small-scale current of rising air, often within a cloud. Overview Localized regions of warm or cool air will exhibit vertical movement. A mass of warm air will typically be less dense than the surrounding region, ...

stretches boundary layer vorticity upward into a vertical axis and tightens it into a strong

vortex In fluid dynamics, a vortex ( : vortices or vortexes) is a region in a fluid in which the flow revolves around an axis line, which may be straight or curved. Vortices form in stirred fluids, and may be observed in smoke rings, whirlpools in th ...

. 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 lower depth, smaller size, and weaker intensity, landspouts are rarely detected by

Doppler weather radar Weather radar, also called weather surveillance radar (WSR) and Doppler weather radar, is a type of radar used to locate precipitation (meteorology), precipitation, calculate its motion, and estimate its type (rain, snow, hail etc.). Modern wea ...

(NWS). Landspouts share a strong resemblance and development process to that of waterspouts, usually taking the form of a translucent and highly

laminar Laminar means "flat". Laminar may refer to: Terms in science and engineering: * Laminar electronics or organic electronics, a branch of material sciences dealing with electrically conductive polymers and small molecules * Laminar armour or "band ...

helical tube. "They are typically narrow, rope-like

condensation Condensation is the change of the state of matter from the gas phase into the liquid phase, and is the reverse of vaporization. The word most often refers to the water cycle. It can also be defined as the change in the state of water vapor to ...

funnels that form while the thunderstorm cloud is still growing and there is no rotating updraft", according to the

National Weather Service The National Weather Service (NWS) is an Government agency, agency of the Federal government of the United States, United States federal government that is tasked with providing weather forecasts, warnings of hazardous weather, and other weathe ...

. Landspouts are considered tornadoes since a rapidly rotating column of air is in contact with both the surface and a

cumuliform cloud Cumulus clouds are clouds which have flat bases and are often described as "puffy", "cotton-like" or "fluffy" in appearance. Their name derives from the Latin ''cumulo-'', meaning ''heap'' or ''pile''. Cumulus clouds are low-level clouds, gene ...

. 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 Orography is the study of the topographic relief of mountains, and can more broadly include hills, and any part of a region's elevated terrain. Orography (also known as ''oreography'', ''orology'' or ''oreology'') falls within the broader discipl ...

can influence landspout (and even mesocyclone tornado) formation. A notable example is the propensity for landspout occurrence in the

Denver Convergence Vorticity Zone The Denver Convergence Vorticity Zone (DCVZ) is an orographically-induced atmospheric phenomenon characterized by convergent winds in the High Plains just east of the Denver metropolitan area, typically in length and oriented in a north-south dir ...

(DCVZ).

Life cycle

Forming in relation to

misocyclone Tornadogenesis is the process by which a tornado forms. There are many types of tornadoes and these vary in methods of formation. Despite ongoing scientific study and high-profile research projects such as VORTEX, tornadogenesis is a volatile pro ...

s 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 In meteorology, an updraft is a small-scale current of rising air, often within a cloud. Overview Localized regions of warm or cool air will exhibit vertical movement. A mass of warm air will typically be less dense than the surrounding region, ...

or significant

precipitation In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls under gravitational pull from clouds. The main forms of precipitation include drizzle, rain, sleet, snow, ice pellets, graupel and hail. ...

(outflow) occur nearby. They may form in lines or groups of multiple landspouts.

Damage

Landspouts are commonly weak; however, on rare occasions, a landspout can be as strong as an

EF2 Elongation factors are a set of proteins that function at the ribosome, during protein synthesis, to facilitate translational elongation from the formation of the first to the last peptide bond of a growing polypeptide. Most common elongation ...

or EF3 tornado.

References

External links

* {{Commonscatinline
Advanced Spotters' Field Guide

Online Tornado FAQ
Severe weather and convection Tornado Vortices fr:Tornade#Trombes terrestres

Characteristics

Life cycle

Damage

See also

References

External links