Landspout

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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.
A landspout near North Platte, Nebraska on May 22, 2004. Note the characteristic smooth, tubular shape, similar to that of a fair-weather waterspout. GID Landspout.jpg
A landspout near North Platte, Nebraska on May 22, 2004. Note the characteristic smooth, tubular shape, similar to that of a fair-weather waterspout.
Landspout on September 29th, 2007 Tornado em Araguari MG 29 set 2007 18 h.JPG
Landspout on September 29th, 2007

Landspout is a term created by atmospheric scientist Howard B. Bluestein in 1985 for a kind of tornado not associated with a mesocyclone. [3] The Glossary of Meteorology defines a landspout as

Contents

"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." [4]

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. 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 (NWS). [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. [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).

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. [6]

Damage

Landspouts are commonly weak; however, on rare occasions, a landspout can be as strong as an EF2 or EF3 tornado.

See also

Related Research Articles

<span class="mw-page-title-main">Tornado</span> Violently rotating column of air in contact with both the Earths surface and a cumulonimbus cloud

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, although the word cyclone is used in meteorology to name a weather system with a low-pressure area in the center around which, from an observer looking down toward the surface of the Earth, winds blow counterclockwise in the Northern Hemisphere and clockwise in the Southern. Tornadoes come in many shapes and sizes, and they are often visible in the form of a condensation funnel originating from the base of a cumulonimbus cloud, with a cloud of rotating debris and dust beneath it. Most tornadoes have wind speeds less than 180 kilometers per hour, are about 80 meters across, and travel several kilometers before dissipating. The most extreme tornadoes can attain wind speeds of more than 480 kilometers per hour (300 mph), are more than 3 kilometers (2 mi) in diameter, and stay on the ground for more than 100 km.

<span class="mw-page-title-main">Cyclone</span> Large scale air mass that rotates around a strong center of low pressure

In meteorology, a cyclone is a large air mass that rotates around a strong center of low atmospheric pressure, counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere as viewed from above. Cyclones are characterized by inward-spiraling winds that rotate about a zone of low pressure. The largest low-pressure systems are polar vortices and extratropical cyclones of the largest scale. Warm-core cyclones such as tropical cyclones and subtropical cyclones also lie within the synoptic scale. Mesocyclones, tornadoes, and dust devils lie within smaller mesoscale. Upper level cyclones can exist without the presence of a surface low, and can pinch off from the base of the tropical upper tropospheric trough during the summer months in the Northern Hemisphere. Cyclones have also been seen on extraterrestrial planets, such as Mars, Jupiter, and Neptune. Cyclogenesis is the process of cyclone formation and intensification. Extratropical cyclones begin as waves in large regions of enhanced mid-latitude temperature contrasts called baroclinic zones. These zones contract and form weather fronts as the cyclonic circulation closes and intensifies. Later in their life cycle, extratropical cyclones occlude as cold air masses undercut the warmer air and become cold core systems. A cyclone's track is guided over the course of its 2 to 6 day life cycle by the steering flow of the subtropical jet stream.

<span class="mw-page-title-main">Supercell</span> Thunderstorm that is characterized by the presence of a mesocyclone

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, supercells are the overall least common and have the potential to be the most severe. Supercells are often isolated from other thunderstorms, and can dominate the local weather up to 32 kilometres (20 mi) away. They tend to last 2–4 hours.

<span class="mw-page-title-main">Mesocyclone</span> Region of rotation within a powerful thunderstorm

A mesocyclone is a meso-gamma mesoscale region of rotation (vortex), typically around 2 to 6 mi in diameter, most often noticed on radar within thunderstorms. In the northern hemisphere it is usually located in the right rear flank of a supercell, or often on the eastern, or leading, flank of a high-precipitation variety of supercell. The area overlaid by a mesocyclone’s circulation may be several miles (km) wide, but substantially larger than any tornado that may develop within it, and it is within mesocyclones that intense tornadoes form.

<span class="mw-page-title-main">Squall line</span> Line of thunderstorms along or ahead of a cold front

A squall line, or more accurately a quasi-linear convective system (QLCS), is a line of thunderstorms, often forming along or ahead of a cold front. In the early 20th century, the term was used as a synonym for cold front. Linear thunderstorm structures often contain heavy precipitation, hail, frequent lightning, strong straight-line winds, and occasionally tornadoes or waterspouts. Particularly strong straight-line winds can occur where the linear structure forms into the shape of a bow echo. Tornadoes can occur along waves within a line echo wave pattern (LEWP), where mesoscale low-pressure areas are present. Some bow echoes can grow to become derechos as they move swiftly across a large area. On the back edge of the rainband associated with mature squall lines, a wake low can be present, on very rare occasions associated with a heat burst.

<span class="mw-page-title-main">Waterspout</span> Intense columnar vortex over a body of water

A waterspout is an intense columnar vortex 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 cloud. In the common form, it is a non-supercell tornado over water having a five-part life cycle: formation of a dark spot on the water surface, spiral pattern on the water surface, formation of a spray ring, development of the visible condensation funnel, and ultimately, decay.

<span class="mw-page-title-main">Wall cloud</span> Cloud formation occurring at the base of a thunderstorm

A wall cloud is a large, localized, persistent, and often abrupt lowering of cloud that develops beneath the surrounding base of a cumulonimbus cloud and from which tornadoes sometimes form. It is typically beneath the rain-free base (RFB) portion of a thunderstorm, and indicates the area of the strongest updraft within a storm. Rotating wall clouds are an indication of a mesocyclone in a thunderstorm; most strong tornadoes form from these. Many wall clouds do rotate; however, some do not.

<span class="mw-page-title-main">Hook echo</span> Weather radar signature indicating tornadic circulation in a supercell thunderstorm

A hook echo is a pendant or hook-shaped weather radar signature as part of some supercell thunderstorms. It is found in the lower portions of a storm as air and precipitation flow into a mesocyclone, resulting in a curved feature of reflectivity. The echo is produced by rain, hail, or even debris being wrapped around the supercell. It is one of the classic hallmarks of tornado-producing supercells. The National Weather Service may consider the presence of a hook echo coinciding with a tornado vortex signature as sufficient to justify issuing a tornado warning.

<span class="mw-page-title-main">Cyclogenesis</span> The development or strengthening of cyclonic circulation in the atmosphere

Cyclogenesis is the development or strengthening of cyclonic circulation in the atmosphere. Cyclogenesis is an umbrella term for at least three different processes, all of which result in the development of some sort of cyclone, and at any size from the microscale to the synoptic scale.

<span class="mw-page-title-main">Funnel cloud</span> Funnel-shaped cloud of condensed water droplets, associated with a rotating column of wind

A funnel cloud is a funnel-shaped cloud of condensed water droplets, associated with a rotating column of wind and extending from the base of a cloud but not reaching the ground or a water surface. A funnel cloud is usually visible as a cone-shaped or needle like protuberance from the main cloud base. Funnel clouds form most frequently in association with supercell thunderstorms, and are often, but not always, a visual precursor to tornadoes. Funnel clouds are visual phenomena, these are not the vortex of wind itself.

<span class="mw-page-title-main">Gustnado</span> Ground vortex formed from a downburst of a thunderstorm

A gustnado is a brief, shallow surface-based vortex which forms within the downburst emanating from a thunderstorm. The name is a portmanteau by elision of "gust front tornado", as gustnadoes form due to non-tornadic straight-line wind features in the downdraft (outflow), specifically within the gust front of strong thunderstorms. Gustnadoes tend to be noticed when the vortices loft sufficient debris or form condensation cloud to be visible although it is the wind that makes the gustnado, similarly to tornadoes. As these eddies very rarely connect from the surface to the cloud base, they are very rarely considered as tornadoes. The gustnado has little in common with tornadoes structurally or dynamically in regard to vertical development, intensity, longevity, or formative process—as classic tornadoes are associated with mesocyclones within the inflow (updraft) of the storm, not the outflow.

<span class="mw-page-title-main">Cumulus Congestus cloud</span> Form of cumulus clouds

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 between cumulus mediocris and cumulonimbus, sometimes producing showers of snow, rain, or ice pellets. Precipitation that evaporates before reaching the surface is virga.

<span class="mw-page-title-main">Lemon technique</span>

The Lemon technique is a method used by meteorologists using weather radar to determine the relative strength of thunderstorm cells in a vertically sheared environment. It is named for Leslie R. Lemon, the co-creator of the current conceptual model of a supercell. The Lemon technique is largely a continuation of work by Keith A. Browning, who first identified and named the supercell.

<span class="mw-page-title-main">Fire whirl</span> Whirlwind induced by and often composed of fire

A fire whirl or fire devil is a whirlwind induced by a fire and often composed of flame or ash. These start with a whirl of wind, often made visible by smoke, and may occur when intense rising heat and turbulent wind conditions combine to form whirling eddies of air. These eddies can contract a tornado-like vortex that sucks in debris and combustible gases.

<span class="mw-page-title-main">Anticyclonic tornado</span> Tornadoes that spin in the opposite direction of normal tornadoes

An anticyclonic tornado is a tornado which rotates in a clockwise direction in the Northern Hemisphere and a counterclockwise direction in the Southern Hemisphere. The term is a naming convention denoting the anomaly from normal rotation which is cyclonic in upwards of 98 percent of tornadoes. Many anticyclonic tornadoes are smaller and weaker than cyclonic tornadoes, forming from a different process, as either companion/satellite tornadoes or nonmesocyclonic tornadoes.

<span class="mw-page-title-main">Tornadogenesis</span> Process by which a tornado forms

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 process and the intricacies of many of the mechanisms of tornado formation are still poorly understood.

<span class="mw-page-title-main">Rear flank downdraft</span> Type of region

The rear flank downdraft (RFD) is a region of dry air wrapping around the back of a mesocyclone in a supercell thunderstorm. These areas of descending air are thought to be essential in the production of many supercellular tornadoes. Large hail within the rear flank downdraft often shows up brightly as a hook on weather radar images, producing the characteristic hook echo, which often indicates the presence of a tornado.

<span class="mw-page-title-main">Horizontal convective rolls</span>

Horizontal convective rolls, also known as horizontal roll vortices or cloud streets, are long rolls of counter-rotating air that are oriented approximately parallel to the ground in the planetary boundary layer. Although horizontal convective rolls, also known as cloud streets, have been clearly seen in satellite photographs for the last 30 years, their development is poorly understood, due to a lack of observational data. From the ground, they appear as rows of cumulus or cumulus-type clouds aligned parallel to the low-level wind. Research has shown these eddies to be significant to the vertical transport of momentum, heat, moisture, and air pollutants within the boundary layer. Cloud streets are usually more or less straight; rarely, cloud streets assume paisley patterns when the wind driving the clouds encounters an obstacle. Those cloud formations are known as von Kármán vortex streets.

Convective storm detection is the meteorological observation, and short-term prediction, of deep moist convection (DMC). DMC describes atmospheric conditions producing single or clusters of large vertical extension clouds ranging from cumulus congestus to cumulonimbus, the latter producing thunderstorms associated with lightning and thunder. Those two types of clouds can produce severe weather at the surface and aloft.

The following is a glossary of tornado terms. It includes scientific as well as selected informal terminology.

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). "The formation of a "landspout" in a "broken-line" squall line in Oklahoma". Preprints, 14th Conf. On Severe Local Storms, Indianapolis, American Meteorological Society. 14 (4): 267–270. Bibcode:1999WtFor..14..558B. doi: 10.1175/1520-0434(1999)014<0558:AHOSSI>2.0.CO;2 .
  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. 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. 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 .