Mammatus clouds
Mammatus clouds – photo by john finney photography

The Mammatus Cloud. A weather Phenomenon

Mammatus clouds are often formed under cumulo-nimbus cloud anvils caused by severe thunderstorms, hail, or unsettled weather. Anvils are the tops of thunderstorm clouds that have turned to ice because of the high level in the atmosphere, they spread out in front of the cumulo-nimbus cloud in the direction the storm is travelling.

Mammatus are typically found forming off the underside of the cumulonimbus thundercloud. These clouds cause thunderstorms, rain, and lightning. They have a hanging appearance and can be quite spectacular, especially if a sunset or sunlight highlights them.

Mammatus (mamma or mammatocumulus), meaning “mammary cloud,” maybe a cellular pattern of pouches hanging underneath the bottom of a cloud, typically cumulonimbus rainclouds, although they’ll be attached to other classes of parent clouds. The name mammatus springs from the Latin mamma (meaning “udder” or “breast”).

Consistent with the WMO International Cloud Atlas, mamma may be an additional cloud feature instead of a genus, species, or sort of cloud. They’re formed by cold air sinking right down to form the pockets contrary to the puffs of clouds rising through warm air convection. These cloud formations were first described in 1894 by William Clement Ley.

Mammatus clouds
Mammatus clouds from tornado warned storm over an abandoned house. South dakota, usa – photographer by aaron groen

Mammatus Cloud Characteristics

Mammatus are most frequently related to anvil clouds and also severe thunderstorms. They often extend from the bottom of a cumulonimbus. Still, They can also be found under altostratus, cirrus clouds, and volcanic ash clouds.

When occurring in cumulonimbus, mammatus clouds are often indicative of a powerful storm. Thanks to the intensely sheared environment during which mammatus form, aviators & pilots are strongly cautioned to avoid cumulonimbus clouds with mammatus. They indicate convectively induced turbulence. Contrails can also produce lobes, but these are incorrectly termed as mammatus.

Mammatus can appear as smooth, ragged, or lumpy lobes and can be opaque or translucent. Because mammatus clouds develop as a grouping of lobes, the way they clump together can vary from an isolated cluster to an area of mammae, which cover many kilometres to being organized along a line and can be composed of unequal or similarly-sized lobes.

The individual mammatus lobe average diameters of 0ne to three kilometres (0.6–1.9 mi) and lengths on the average of 1⁄2 kilometre (0.3 mi). A lobe can last a mean of 10 minutes, but an entire cluster of mamma can range from a quarter-hour to a couple of hours. They’re usually composed of ice but can also be a mix of ice and liquid water or be composed of virtually entirely liquid water.

Mammatus clouds
Mammatus clouds over nebraska after a tornado. Photographer by jorn c. Olsen

True to their ominous & spectacular appearance, mammatus clouds are often harbingers of a coming storm or a decaying storm or other extreme weather systems. Typically composed primarily of ice, they will extend for many miles or kilometres in each direction, and individual formations can remain to be visibly static for ten to fifteen minutes at a time.

While they’ll appear foreboding, they’re merely the messengers – appearing around, before or maybe after severe weather or thunderstorms.

Mammatus clouds are pouch-like protrusions hanging from clouds’ undersides, usually thunderstorm anvil clouds and other sorts of clouds. Composed primarily of ice, these cloud pouches can extend many miles in any direction, remaining visible in your sky for perhaps ten or quarter-hour at a time.

People associate them with severe weather, and it’s true they will appear around, before or after a storm. Contrary to myth, they don’t continue extending downward to make tornados. Still, they’re interesting partially because they’re formed by sinking air.

Most clouds are formed by rising air. Mammatus clouds can appear ominous. But, in a way that’s so common in nature, their dangerous aspect goes hand in hand with impressive beauty.

Mammatus clouds are an intriguing enigma of atmospheric fluid dynamics and cloud physics. Most typically observed on cumulonimbus anvils, mammatus also occur on the underside of cirrus, cirrocumulus, altocumulus, altostratus, and stratocumulus, also as in contrails from jet aircraft and pyrocumulus ash clouds from volcanic eruptions.

Despite their aesthetic appearance, mammatus are the topic of a few quantitative research studies. Observations of mammatus are mainly obtained through serendipitous opportunities with one observing system (e.g., aircraft penetrations, visual observations, lidar, radar) or tangential observations from field programs other objectives.

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Theories describing mammatus remain untested, as adequate measurements for validation don’t exist due to the tiny distance scales and short time scales of mammatus. Modeling studies of mammatus are virtually nonexistent. As a result, relatively little is understood or known about the environment, formation mechanisms, properties, microphysics, and dynamics of mammatus.

What are mammatus clouds?

Mammatus clouds are a number of the most intriguing and unusual, and distinctive clouds formations with a series of bulges, lobes, or pouches emerging from the base of the anvil of a cloud. The form of mammatus formations can vary widely, from the classic protruding ball or lobe shape to a more elongated tube hanging from the cloud above.

How do mammatus clouds form?

Mammatus clouds are normally formed in unsettle weather and are associated with large cumulonimbus clouds or thunderstorms.

Typically, turbulence within the cumulonimbus will cause mammatus to form up their shape, especially on the projecting anvil’s underside because it rapidly descends to lower levels. This reverses the standard cloud-forming process of upward growth, making for an uneven cloud base.

What weather is related to the mammatus cloud?

Mammatus often forms in association with Cumulonimbus clouds, which successively bring thunderstorms thanks to their vast, unstable air.

What are mammatus clouds a sign of?

Mammatus clouds are a strange weather phenomenon that generally forms within the most unstable cumulonimbus, meaning that there’s also an opportunity of hail, heavy rain, and lightning within the vicinity. If the air is cold enough in the winter or the colder months, they will produce snow. Occasionally, mammatus may form on other cloud types, making no rain, though this is often far less common.

Mammatus can also indicate a decaying thunderstorm or cumulonimbus cloud, as these clouds have been observed quite often on thunderstorms that are dissipating. So these strange clouds can also mean severe weather systems that are about to break to fine weather or more stable weather patterns.

The word Mammatus comes from the Latin mamma, which translates to “udder” or “breast.” The striking cloud’s appearance is most visible when it’s sunrise or sunset or when the sun is low within the sky, and the daylight frames their pouches. This extra feature may be a firm favourite with many meteorologists, likewise as cloud and photography enthusiasts.

Mammatus clouds
Mammatus clouds – photo by john finney photography

Are mammatus clouds dangerous?

A mammatus cloud area can stretch for dozens of kilometres across the sky. The cloud droplets & ice crystals eventually dissipate, & so do the mammatus clouds.
Even though the clouds themselves are harmless, they are often early warning signs of a dangerous thunderstorm nearby, so if you see them in the sky, take action to secure loose items and put vehicles under cover.

What clouds are associated with mammatus?

Mammatus usually form on the bottom of a cumulonimbus anvil. They have been observed and sighted to form or develop on other cloud types, like stratocumulus, altostratus, and altocumulus. Mammatus have also been observed to expand on the underside of volcanic ash clouds.

What Causes Mammatus Clouds?

The accurate causes of these clouds are still to this day not entirely certain. There are several theories as to the development and causes of these clouds that have been documented by several meteorologists and they can be found on this Wikipedia page:

Mammatus Clouds are an enduring weather phenomenon produced by mother nature and still to this day elude us as to the exact cause of these strange cloud formations. The weather and its characteristics are as mysterious to me as a weather enthusiast as it was when I was a child.

I used to watch storms and cyclones coming in from afar from a local weather radar or on the news and admire how beautiful and devastating weather systems and severe thunderstorms can be. These unique cloud formations prove to me that nature continues to throw unexplained occurrences of nature at us every day all over the world.

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