Cumulonimbus calvus represents a transitional stage between cumulus congestus and a fully fledged cumulonimbus incus.
A cumulonimbus incus formation must always be regarded as a significant aviation hazard because of the powerful air currents involved in its formation and the potentially damaging effect of the large hailstones it may produce.
Mammatus may be observed wherever cumulonimbusclouds occur, but it is particularly common in areas where thunderstorms are severe, such as tropical and subtropical areas.
Mammatus Clouds - Crystalinks(Site not responding. Last check: 2007-10-09)
Mammatus (also known as mamma or mammatocumulus, meaning "breast-cloud") is a meteorological term applied to a cellular pattern of pouches hanging underneath the base of a cloud, often a cumulus or cumulonimbus.
Mammatus only occur where cumulonimbus are present; however, they can drift up to 25 miles away from a thunderstorm.
It is very common for storms producing mammatusclouds also to produce wind shear, and possibly - though less likely - ball lightning; therefore, aviators are strongly cautioned to avoid cumulonimbus with mammatus.
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While mammatusclouds usually form beneath weakening thunderstorms, the kinds of thunderstorms that have them at one time contained intense updrafts, which indicates conditions in the area were, and might still be, favorable for severe weather.
However, mammatusclouds sometimes form on the upwind, or backside, of severe thunderstorms that at the same time are dropping large hail and unleashing 60-70 mph bursts of wind.
Cumulonimbus with mammatus formed after Cyclone Catarina in Santa Catarina, Brazil, 2004
Contrary to common misconceptions, mammatus are not precursors to tornadoes, but are a possible byproduct [1].
It is very common for storms producing mammatusclouds also to produce wind shear, and possibly—though less likely—Ball lightning; therefore, aviators are strongly cautioned to avoid cumulonimbus with mammatus.
The updrafts in these clouds range from brief puffs of a few meters per second (5-10 mph) in small Cumulus and Cumulonimbusclouds (see 5A, 5B, 6A, and 6C) to sustained updrafts of 30 m/s (65 mph) or more in the most powerful thunderstorms (see 6B, 6D and 6E).
Cumulonimbusclouds are the Tyrannosaurus rexes of the cloud world.
The smallest Cumulonimbusclouds form in polar air (see 6A and 6C) and can be less than 2 km thick.
Cumulonimbus (CB), where the upper part of at least one of the CB clouds in clearly fibrous or striated.
By convention, code figure 9 is used for CumulonimbusMammatus (CBMAM) and those cases in which lightning, thunder, or hail indicates the presence of a CB but the top is hidden by darkness or other clouds.
Dense cirrus (CI) (often in the form of an anvil) originating from cumulonimbus (CB).
AOSS202 - Main Page(Site not responding. Last check: 2007-10-09)
OK, they may be man-made but they still classify as cirrus.
Mammatus, located on the anvil of a cumulonimbus (but only mammatus gets you points).
This is a dust storm moving across Australia, sometimes produced as a gust front from a nearby storm, other times it provides a stunning visualization of a cold front.