A cumulonimbus incus (), also called an anvil cloud, is a

cumulonimbus cloud Cumulonimbus () is a dense, towering, vertical cloud, typically forming from water vapor condensing in the lower troposphere that builds upward carried by powerful buoyant air currents. Above the lower portions of the cumulonimbus the water ...

that has reached the level of stratospheric stability and has formed the characteristic flat,

anvil An anvil is a metalworking tool consisting of a large block of metal (usually Forging, forged or Steel casting, cast steel), with a flattened top surface, upon which another object is struck (or "worked"). Anvils are massive because the hi ...

-shaped

top Top most commonly refers to: * Top, a basic term of orientation, distinguished from bottom, front, back, and sides * Spinning top, a ubiquitous traditional toy * Top (clothing), clothing designed to be worn over the torso * Mountain top, a moun ...

. It signifies a

thunderstorm A thunderstorm, also known as an electrical storm or a lightning storm, is a storm characterized by the presence of lightning and its acoustics, acoustic effect on the Earth's atmosphere, known as thunder. Relatively weak thunderstorm ...

in its mature stage, succeeding the

cumulonimbus calvus Cumulonimbus calvus is a moderately tall cumulonimbus cloud that is capable of precipitation but has not yet reached the tropopause, which is the height of stratospheric stability at which cumulonimbus forms into cumulonimbus capillatus (fibrous- ...

stage. Cumulonimbus incus is a subtype of cumulonimbus capillatus. These clouds are commonly associated with severe weather, including heavy rain,

downburst In meteorology, a downburst is a strong downward and outward gushing wind system that emanates from a point source above and blows radially, that is, in straight lines in all directions from the area of impact at surface level. It originate ...

s, and occasionally a

tornado A tornado is a violently rotating column of air that is in contact with the surface of 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 ...

Hazards

A cumulonimbus incus is a mature thunderstorm cloud generating many dangerous elements. *

Lightning Lightning is a natural phenomenon consisting of electrostatic discharges occurring through the atmosphere between two electrically charged regions. One or both regions are within the atmosphere, with the second region sometimes occurring on ...

: this storm cloud is capable of producing bursts of cloud-to-ground lightning. *

Hail Hail is a form of solid Precipitation (meteorology), precipitation. It is distinct from ice pellets (American English "sleet"), though the two are often confused. It consists of balls or irregular lumps of ice, each of which is called a hailsto ...

: hailstones may fall from this cloud if it is a highly unstable environment (which favours a more vigorous storm

updraft In meteorology, an updraft (British English: ''up-draught'') is a small-scale air current, current of rising air, often within a cloud. Overview Vertical drafts, known as updrafts or downdrafts, are localized regions of warm or cool air that mov ...

). *Heavy

rain Rain is a form of precipitation where water drop (liquid), droplets that have condensation, condensed from Water vapor#In Earth's atmosphere, atmospheric water vapor fall under gravity. Rain is a major component of the water cycle and is res ...

: this cloud may drop several inches (centimetres) of rain in a short amount of time. This can cause

flash flood A flash flood is a rapid flooding of low-lying areas: washes, rivers, dry lakes and depressions. It may be caused by heavy rain associated with a severe thunderstorm, hurricane, or tropical storm, or by meltwater from ice and snow. Flash f ...

ing. *Strong

wind Wind is the natural movement of atmosphere of Earth, air or other gases relative to a planetary surface, planet's surface. Winds occur on a range of scales, from thunderstorm flows lasting tens of minutes, to local breezes generated by heatin ...

: gale-force winds from a

may occur under this cloud. *

Tornadoes A tornado is a violently rotating column of air that is in contact with the surface of 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 ...

: in severe cases (most commonly with

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 (su ...

s), it can produce tornadoes. They are not directly produced by cumulonimbus incus but rather produced by supercells which come from cumulonimbus incus.

Classification

Cumulonimbus clouds can be powerful. If the correct atmospheric conditions are met, they can grow into a

storm. This cloud may be a

single-cell thunderstorm A pulse storm is a Storm cell, single cell thunderstorm of substantial intensity which only produces severe weather for short periods of time. Such a storm weakens and then generates another short burst – hence "pulse". The term was coined by res ...

or one cell in a

multicellular thunderstorm A multicellular thunderstorm cluster is a thunderstorm that is composed of multiple convective cells, each being at a different stage in the life cycle of a thunderstorm. It appears as several anvils clustered together. A cell is an updraft/down ...

. They are capable of producing severe storm conditions for a short amount of time.

References

External links

{{Cloud types Cumulus Cirrus fr:Cumulonimbus#Cumulonimbus capillatus et incus