Altostratus undulatus cloud

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**Altostratus undulatus cloud**
Cirrus and Altostratus undulatus clouds
Altitude	2400-6100 m (8,000-20,000 ft)
Appearance	undulated
Precipitation Cloud?	no
Abbreviation	As

The altostratus undulatus is a type of low altocumulus cloud with signature undulations within it. These undulations may be visible (usually as "wavy bases"), but frequently they are indiscernable to the naked eye. These formations will generally appear in the early stages of destabilizing return flows, especially over the southern plains of the United States, when the surface temperature is still relatively cool.[1] The wavy strips of clouds are generally near an inversion surface.

Also referred to as "billow clouds," "windrow clouds," or "wave clouds," variations of the undulatus can be elements that have merged or single elements that have stretched through the sky. They often run parallel, but can also appear to interweave across the sky, especially if dual wave systems are seen (also referred to as biundulatus). Gravity waves aligned normally to the direction of the wind can show wide, near-parallel cloud strips.[2]

[edit] See also

[edit] External links

American Meteorological Society's Glossary of Meteorology
Stormeyes, a website for storm watchers (and storm chasers)
Weather Photography

v • d • e Clouds
High Clouds (Family A):	Cirrus (Ci) • Cirrus uncinus • Cirrus Kelvin-Helmholtz colombia • Cirrostratus (Cs) • Cirrocumulus (Cc) • Pileus • Contrail
Middle Clouds (Family B):	Altostratus (As) • Altostratus undulatus • Altocumulus (Ac) • Altocumulus undulatus • Altocumulus mackerel sky • Altocumulus castellanus cloud • Altocumulus lenticularis
Low Clouds (Family C):	Stratus (St) • Nimbostratus (Ns) • Cumulus humilis (Cu) • Cumulus mediocris (Cu) • Stratocumulus (Sc)
Vertical Clouds (Family D):	Cumulonimbus (Cb) • Cumulonimbus incus • Cumulonimbus calvus • Cumulonimbus with mammatus • Cumulus congestus • Pyrocumulus • Pyrocumulonimbus