Cumulonimbus cloud

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Cumulonimbus cloud
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Genus Cumulonimbus (heaped, rain)
Altitude460–7,620–12,190 m
(1,500 – 25,000-40,200 ft)
AppearanceVery tall and large clouds
Precipitation cloud?Yes, often intense

Cumulonimbus (from Latin cumulus, "heaped" and nimbus, "rainstorm") is a dense, towering vertical cloud, [1] forming from water vapor carried by powerful upward air currents. If observed during a storm, these clouds may be referred to as thunderheads. Cumulonimbus can form alone, in clusters, or along cold front squall lines. These clouds are capable of producing lightning and other dangerous severe weather, such as tornadoes. Cumulonimbus progress from overdeveloped cumulus congestus clouds and may further develop as part of a supercell. Cumulonimbus is abbreviated Cb.

Latin Indo-European language of the Italic family

Latin is a classical language belonging to the Italic branch of the Indo-European languages. The Latin alphabet is derived from the Etruscan and Greek alphabets and ultimately from the Phoenician alphabet.

Cloud visible mass of liquid droplets or frozen crystals suspended in the atmosphere

In meteorology, a cloud is an aerosol consisting of a visible mass of minute liquid droplets, frozen crystals, or other particles suspended in the atmosphere of a planetary body or similar space. Water or various other chemicals may compose the droplets and crystals. On Earth, clouds are formed as a result of saturation of the air when it is cooled to its dew point, or when it gains sufficient moisture from an adjacent source to raise the dew point to the ambient temperature. They are seen in the Earth's homosphere. Nephology is the science of clouds, which is undertaken in the cloud physics branch of meteorology.

Squall line

A squall line or quasi-linear convective system (QLCS) is a line of thunderstorms forming along or ahead of a cold front. In the early 20th century, the term was used as a synonym for cold front. It contains heavy precipitation, hail, frequent lightning, strong straight-line winds, and possibly tornadoes and waterspouts. Strong straight-line winds can occur where the squall line is in 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 which develop within the summer season are known as derechos, and they move quite fast through large sections of territory. On the back edge of the rainband associated with mature squall lines, a wake low can be present, sometimes associated with a heat burst.



Towering cumulonimbus clouds are typically accompanied by smaller cumulus clouds. The cumulonimbus base may extend several miles across and occupy low to middle altitudes - formed at altitude from approximately 200 to 4,000 m (700 to 10,000 ft). Peaks typically reach to as much as 12,000 m (39,000 ft), with extreme instances as high as 21,000 m (69,000 ft) or more. [2] Well-developed cumulonimbus clouds are characterized by a flat, anvil-like top (anvil dome), caused by wind shear or inversion near the tropopause. The shelf of the anvil may precede the main cloud's vertical component for many miles, and be accompanied by lightning. Occasionally, rising air parcels surpass the equilibrium level (due to momentum) and form an overshooting top culminating at the maximum parcel level. When vertically developed, this largest of all clouds usually extends through all three cloud regions. Even the smallest cumulonimbus cloud dwarfs its neighbors in comparison.

Cumulus cloud genus of clouds, low-level 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, generally less than 2,000 m (6,600 ft) in altitude unless they are the more vertical cumulus congestus form. Cumulus clouds may appear by themselves, in lines, or in clusters.

Anvil metalworking tool consisting of large block of metal (usually forged or cast steel), with a flattened top surface, upon which another object is struck

An anvil is a metalworking tool consisting of a large block of metal, with a flattened top surface, upon which another object is struck.

Inversion (meteorology) deviation from the normal change of an atmospheric property with altitude

In meteorology, an inversion, also known as a temperature inversion, is a deviation from the normal change of an atmospheric property with altitude. It almost always refers to an inversion of the thermal lapse rate. Normally, air temperature decreases with an increase in altitude. During an inversion, warmer air is held above cooler air; the normal temperature profile with altitude is inverted.


Cumulonimbus calvus cloud species

Cumulonimbus calvus is a moderately tall cumulonimbus cloud which is capable of precipitation, but has not yet reached the tropopause, which is the height of stratospheric stability where it forms into a cumulonimbus capillatus (fibrous-top) or cumulonimbus incus (anvil-top). Cumulonimbus calvus clouds develop from cumulus congestus, and its further development under auspicious conditions will result in cumulonimbus incus.

Supplementary features

Accessory clouds

  • Arcus (including roll and shelf clouds): low, horizontal cloud formation associated with the leading edge of thunderstorm outflow. [4]
  • Pannus: accompanied by a lower layer of fractus species cloud forming in precipitation. [5]
  • Pileus (species calvus only): small cap-like cloud over parent cumulonimbus.
  • Velum: a thin horizontal sheet that forms around the middle of a cumulonimbus. [6]

An arcus cloud is a low, horizontal cloud formation, usually appearing as an accessory cloud to a cumulonimbus. Roll clouds and shelf clouds are the two main types of arcus. Arcus clouds most frequently form along the leading edge or "gust fronts" of thunderstorm outflow; some of the most dramatic arcus formations mark the gust fronts of derecho-producing convective systems. Roll clouds also may arise in the absence of thunderstorms, forming along the shallow cold air currents of some sea breeze boundaries and cold fronts.

Fractus cloud Cloud species

Fractus clouds (scuds) are small, ragged cloud fragments that are usually found under an ambient cloud base. They form or have broken off from a larger cloud, and are generally sheared by strong winds, giving them a jagged, shredded appearance. Fractus have irregular patterns, appearing much like torn pieces of cotton candy. They change constantly, often forming and dissipating rapidly. They do not have clearly defined bases. Sometimes they are persistent and form very near the surface. Common kinds include scud and cloud tags.

Pileus (meteorology) clouds supplementary feature

A pileus, also called scarf cloud or cap cloud, is a small, horizontal, lenticular cloud appearing above a cumulus or cumulonimbus cloud. Pileus clouds are often short-lived, with the main cloud beneath them rising through convection to absorb them. They are formed by strong updraft at lower altitudes, acting upon moist air above, causing the air to cool to its dew point. As such, they are usually indicators of severe weather, and a pileus found atop a cumulus cloud often foreshadows transformation into a cumulonimbus cloud, as it indicates a strong updraft within the cloud.

Supplementary features

  • Incus (species capillatus only): cumulonimbus with flat anvil-like cirriform top caused by wind shear where the rising air currents hit the inversion layer at the tropopause. [7]
  • Mamma or mammatus: consisting of bubble-like protrusions on the underside.
  • Tuba: column hanging from the cloud base which can develop into a funnel cloud or tornado. They are known to drop very low, sometimes just 20 feet (6 m) above ground level. [6]
  • Flanking line is a line of small cumulonimbus or cumulus generally associated with severe thunderstorms.
Cumulonimbus incus variety of cloud

A cumulonimbus incus also known as an anvil cloud is a cumulonimbus cloud which has reached the level of stratospheric stability and has formed the characteristic flat, anvil-top shape. It signifies the thunderstorm in its mature stage, succeeding the cumulonimbus calvus stage. Cumulonimbus incus is a sub-form of Cumulonimbus capillatus.

Mammatus cloud clouds supplementary feature

Mammatus, meaning "mammary cloud", is a cellular pattern of pouches hanging underneath the base of a cloud, typically cumulonimbus rainclouds, although they may be attached to other classes of parent clouds. The name mammatus is derived from the Latin mamma. According to the WMO International Cloud Atlas, mamma is a cloud supplementary feature rather than a genus, species or variety of cloud. They are formed by cold air sinking down to form the pockets contrary to the puffs of clouds rising through the convection of warm air. These formations were first described in 1894 by William Clement Ley.

Funnel cloud 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.

Precipitation-based supplementary features

  • Rain: precipitation that reaches the ground as liquid, often in a precipitation shaft. [8]
  • Virga: precipitation that evaporates before reaching the ground. [6]


Cumulonimbus storm cells can produce torrential rain of a convective nature (often in the form of a rain shaft) and flash flooding, as well as straight-line winds. Most storm cells die after about 20 minutes, when the precipitation causes more downdraft than updraft, causing the energy to dissipate. If there is enough solar energy in the atmosphere, however (on a hot summer day, for example), the moisture from one storm cell can evaporate rapidly—resulting in a new cell forming just a few miles from the former one. This can cause thunderstorms to last for several hours. Cumulonimbus clouds can also bring dangerous winter storms (called "blizzards") which bring lightning, thunder, and torrential snow. However, cumulonimbus clouds are most common in tropical regions. [9]

Life cycle or stages

In general, cumulonimbus require moisture, an unstable air mass, and a lifting force (heat) in order to form. Cumulonimbus typically go through three stages: the developing stage, the mature stage (where the main cloud may reach supercell status in favorable conditions), and the dissipation stage. [10] The average thunderstorm has a 24 km (15 mi) diameter. Depending on the conditions present in the atmosphere, these three stages take an average of 30 minutes to go through. [11]

Stages of a cumulonimbus cloud's life. Thunderstorm formation.jpg
Stages of a cumulonimbus cloud's life.
Towering vertical cumulonimbus capillatus with anvil-shaped incus supplementary feature. High layer of cirrus spissatus near top of image. Anvil cumulus feb 2007.jpg
Towering vertical cumulonimbus capillatus with anvil-shaped incus supplementary feature. High layer of cirrus spissatus near top of image.

Cloud types

Clouds form when the dewpoint of water is reached in the presence of condensation nuclei in the troposphere. The atmosphere is a dynamic system, and the local conditions of turbulence, uplift and other parameters give rise to many types of clouds. Various types of cloud occur frequently enough to have been categorized. Furthermore, some atmospheric processes can make the clouds organize in distinct patterns such as wave clouds or actinoform clouds. These are large-scale structures and are not always readily identifiable from a single point of view.

See also

Related Research Articles

Altocumulus cloud genus of clouds

Altocumulus is a middle-altitude cloud genus that belongs mainly to the stratocumuliform physical category characterized by globular masses or rolls in layers or patches, the individual elements being larger and darker than those of cirrocumulus and smaller than those of stratocumulus. However, if the layers become tufted in appearance due to increased airmass instability, then the altocumulus clouds become more purely cumuliform in structure. Like other cumuliform and stratocumuliform clouds, altocumulus signifies convection. A sheet of partially conjoined altocumulus perlucidus is sometimes found preceding a weakening warm front, where the altostratus is starting to fragment, resulting in patches of altocumulus perlucidus between the areas of altostratus. Altocumulus is also commonly found between the warm and cold fronts in a depression, although this is often hidden by lower clouds.

Altostratus cloud genus of clouds

Altostratus is a middle altitude cloud genus belonging to the stratiform physical category characterized by a generally uniform gray to bluish-green sheet or layer. It is lighter in color than nimbostratus and darker than high cirrostratus. The sun can be seen through thin altostratus, but thicker layers can be quite opaque.

Stratocumulus cloud genus of clouds

A stratocumulus cloud belongs to a genus-type of clouds characterized by large dark, rounded masses, usually in groups, lines, or waves, the individual elements being larger than those in altocumulus, and the whole being at a lower height, usually below 2,000 metres (6,600 ft). Weak convective currents create shallow cloud layers because of drier, stable air above preventing continued vertical development.

Nimbostratus cloud genus of clouds

A nimbostratus cloud or nimbostratus is a low, gray, often dark, amorphous, nearly uniform cloud that usually produces continuous rain, snow, or sleet and no lightning or thunder.

Cumulus humilis cloud cloud species

Cumulus humilis are cumuliform clouds with little vertical extent, common in the summer, that are often referred to as "fair weather cumulus". If they develop into cumulus mediocris or cumulus congestus, thunderstorms could form later in the day.

Accessory cloud

An accessory cloud is a cloud which is dependent on a larger cloud system for its development and continuance. It is often an appendage but also can be adjacent to the parent cloud system.

Cumulus mediocris cloud cloud species

Cumulus mediocris is a low to middle level cloud with some vertical extent of the genus cumulus, larger in vertical development than Cumulus humilis. It also may exhibit small protuberances from the top and may show the cauliflower form characteristic of cumulus clouds. Cumulus mediocris clouds do not generally produce precipitation of more than very light intensity, but can further advance into clouds such as Cumulus congestus or Cumulonimbus, which do produce precipitation.

This is a list of meteorology topics. The terms relate to meteorology, the interdisciplinary scientific study of the atmosphere that focuses on weather processes and forecasting.

Cumulus congestus cloud cloud species

Cumulus congestus clouds, also known as towering cumulus, are a form of cumulus cloud 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.

Overshooting top part of the anvil of a thunderstorm

An overshooting top is a dome-like protrusion shooting out of the top of the anvil of a thunderstorm. When an overshooting top is present for 10 minutes or longer, it's a strong indication the storm is severe.

Air-mass thunderstorm

An air-mass thunderstorm, also called an "ordinary", "single cell", or "garden variety" thunderstorm, is a thunderstorm that is generally weak and usually not severe. These storms form in environments where at least some amount of Convective Available Potential Energy (CAPE) is present, but very low levels of wind shear and helicity. The lifting source, which is a crucial factor in thunderstorm development, is usually the result of uneven heating of the surface, though they can be induced by weather fronts and other low-level boundaries associated with wind convergence. The energy needed for these storms to form comes in the form of insolation, or solar radiation. Air-mass thunderstorms do not move quickly, last no longer than an hour, and have the threats of lightning, as well as showery light, moderate, or heavy rainfall. Heavy rainfall can interfere with microwave transmissions within the atmosphere.

The maximum parcel level (MPL) is the highest level in the atmosphere that a moist convectively rising air parcel will reach after ascending from the level of free convection (LFC) through the free convective layer (FCL) and reaching the equilibrium level (EL), near the tropopause. As the parcel rises through the FCL it expands adiabatically causing its temperature to drop, often below the temperature of its surroundings, and eventually lose buoyancy. Because of this, the EL is approximately the region where the distinct flat tops, often observed around the upper portions of cumulonimbus clouds. If the air parcel ascended quickly enough then it retains momentum after it has cooled and continues rising past the EL, ceasing at the MPL.

Cumulonimbus capillatus cloud species

A Cumulonimbus capillatus is a cumulonimbus cloud with dense cirrus clouds which makes the cloud's top appear to contain hair-like structures. It is an intermediate stage between cumulonimbus calvus and cumulonimbus incus.

Precipitation shaft

A precipitation shaft is a weather phenomenon, visible from the ground at large distances from the storm system, as a dark vertical shaft of heavy rain, hail, or snow, generally localized over a relatively small area.

Flanking line (meteorology)

A flanking line is an area of cumulus congestus or small cumulonimbus that mark an area of widespread updrafts in front of strong thunderstorms. These flanking lines generally occur in the vicinity of supercell thunderstorms or large multicell thunderstorms.


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  9. "Flying through 'Thunderstorm Alley'".
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