Wall cloud
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A wall cloud is a large, localized, persistent, and often abrupt lowering of cloud that develops beneath the surrounding base of a cumulonimbus cloud and from which tornadoes sometimes form. It is typ
A rain-free base with a wall cloud lowering in the foreground and precipitation in the background. Taken in Needmore, Texas.
A wall cloud with tail cloud.
A shelf cloud over Enschede, Netherlands
A tornadic wall cloud with RFD clear slot.
Arcus cloud
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An arcus cloud is a low, horizontal cloud formation, usually appearing as an accessory cloud to a cumulonimbus. Roll clouds and shelf clouds are the two main types of arcus clouds. They most frequentl
Wall cloud
…and is often mistaken for tornadoes. Although the presence of a flumen is associated with tornado risk, the flumen does not rotate. Many storms contain shelf clouds, which are often mistaken for wall clouds since an approaching shelf cloud appears to form a wall made of clouds and may contain turbulent motions…
A striated shelf cloud, in Massachusetts in July 2022
Underside of a weak shelf cloud
A shelf cloud in Durango, Mexico