Cumulonimbus cloud

Cumulonimbus clouds
Cumulonimbus capillatus incus
Abbreviation	Cb
Symbol
Genus	Cumulonimbus (heap, cloud/severe rain)
Altitude	2,000–16,000 m (6,500–60,000 ft)
Classification	Family D (Vertically developed)
Appearance	Very tall and large clouds
Precipitation cloud?	Yes, often intense, but may be virga (virga—occasionally a streak of precipitation but evaporates before it hits the ground)

Cumulonimbus (from the Latin cumulus ("heap") and nimbus ("cloud") is a dense towering vertical cloud associated with thunderstorms and atmospheric instability, forming from water vapour carried by powerful upward air currents. Cumulonimbus may form alone, in clusters, or along cold front squall lines. They may produce lightning and other dangerous severe weather, such as gusts and hail. Cumulonimbus progress from over-developed cumulus congestus clouds, and may further develop as part of a supercell. Cumulonimbus is abbreviated Cb, and are designated in the D2 family.

Appearance

An exceptionally clearly-developed single-cell Cumulonimbus incus Big displaying the classic anvil shape; associated gusts may occur from the direct proximity to several times the height of the cloud.

Cumulonimbus capillatus incus

Cumulonimbus clouds typically are accompanied by lower altitude cumulus clouds, growing vertically instead of horizontally, contributing to the mushroom shape of the cumulonimbus. The cumulonimbus base may extend several miles across and occupy low to middle altitudes- formed at altitude from approximately 500 to 13,000 feet (150 to 3,960 meters). Peaks typically reach to as much as 20,000 feet (6,090 meters), with extreme instances as high as 75,000 feet (23,000 meters). Well-developed cumulonimbus clouds are characterised 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 neighbours in comparison.

Species

• Cumulonimbus arcus.
• Cumulonimbus calvus: cloud with puffy top, similar to cumulus congestus, but larger;
• Cumulonimbus capillatus - cloud with cirrus-like, fibrous-edged top;
• Cumulonimbus incus: subtype of Cumulonimbus capillatus, with flat anvil-like top.
• Cumulonimbus mammatus.
• Cumulonimbus pannus.
• Cumulonimbus pileus.
• Cumulonimbus praecipitatio.
• Cumulonimbus tuba.
• Cumulonimbus velum.
• Cumulonimbus virga.

Effects

See also: Severe weather and Thunderstorm

Cumulonimbus storm cells can produce torrential rain of a convective nature 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's 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.

Cloud types

Main article: List of 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 clouds 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 single point of view.

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  Calvus type Cumulonimbus cloud.

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  Cumulonimbus cloud in central Oklahoma. The updraft is the large cloud mass at the center of the photo.

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  Cumulonimbus cloud over White Canyon in Utah

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  Cumulonimbus incus cloud formation with anvil over Margalla Hills, Islamabad. A cirrus cloud has formed from a part of the anvil that has been broken off.

See also

• Atmospheric convection
• Atmospheric thermodynamics
• Convective instability
• Funnel cloud
• Hot tower
• Pyrocumulonimbus

External links

• Clouds-Online.com Cloud Atlas with many photos and description of the different cloud genus
• Cumulonimbus cloud at BBC Weather
• Weather Pictures and Storm Chasing – Cumulonimbus clouds