An isolated, lowered cloud base that descends from the rain-free portion of a severe thunderstorm, marking the storm's main rotating updraft and often the area from which a tornado, if one forms, will develop. Wall clouds typically persist for ten to twenty minutes and can exhibit visible rotation, making them a key visual cue storm spotters watch for when assessing a supercell's tornado potential.
Facts
Identification
Distinguishing AppearanceA dark cloud feature protruding from the base of a cumulonimbus. 1 ScaleFrom a fraction of 1 mi (1.6 km) wide to over 5 mi (8 km) across. 1 Connections
Associated With
A wall cloud is the lowered, often rotating cloud base beneath a supercell thunderstorm from which many tornadoes descend, and is used operationally as a warning sign of tornado formation.
Sources
1. Wall cloud, Wikipedia
Structure
A dark cloud feature that protrudes from the base of a cumulonimbus more popularly known as a wall cloud.
Structure, size
Wall clouds can be anywhere from a fraction of 1 mi (1.6 km) wide to over 5 mi (8 km) across.
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