Pileus (cloud)

Clouds : classification
Genera Cirrus Ci Cirrocumulus Cc Cirrostratus Cs Altocumulus Ac Altostratus As Stratocumulus Sc Stratus St. Cumulus Cu Nimbostratus Ns Cumulonimbus Cb	species calvus cal capillatus cap castellanus cas congestus con fibratus fib floccus flo fractus fra humilis hum lenticularis len mediocris med nebulosus neb spissatus spi stratiformis st uncinus unc volutus vol	Subspecies duplicatus you intortus in lacunosus la opacus op perlucidus pe radiatus ra translucidus tr undulatus un vertebratus ve Special forms arcus arc asperitas asp cauda cau cavum cav fluctus flu flumen flm incus inc mamma mam murus mur pannus pan pileus pil praecipitatio pra tuba tub velum vel virga vir

Cumulonimbus with pileus over Lake Constance

Pileus ( Latin "cap", abbreviation pil ) is an accompanying cloud of small horizontal extent in the form of a cap or hood over the cloud top or directly on the upper part of a cumulus-like cloud , by which it is often pierced. Pilei tend to change their appearance very quickly. They arise when the air at the top of the cumulus is very humid and is lifted by the cloud, which continues to swell. They can be seen as precursors of a transformation of cumulus into cumulonimbus clouds and thus signal the possible formation of showers or thunderstorms. Pilei only occur with these two types of cloud and can often be observed on top of each other. They also occur during volcanic eruptions .

Development of a pileus in pictures

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  Pileus July 27, 2005 7:37 p.m.

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  Pileus July 27, 2005 7:37 p.m.

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  Pileus July 27, 2005 7:38 p.m.

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  Pileus July 27, 2005 7.41 p.m.

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  Pileus July 27, 2005 7.41 p.m.

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  Pileus in the state of disintegration July 27, 2005 7.43 p.m.

Web links

Pilei girding and crowning a cumulonimbus, so to speak

Commons : Pileus  - album with pictures, videos and audio files