Shelf Cloud slopes downward and away from the rain area
This is the first of four photographs of an approaching thunderstorm to help visualize the difference between gust front outflow "push" and wall cloud inflow "pull.
Shelf Cloud - a low, horizontal wedge-shaped arcus cloud, associated with a thunderstorm gust front (or occasionally with a cold front, even in the absence of thunderstorms).
Shelf Cloud - A low-level horizontal accessory cloud that appears to be wedge-shaped as it approaches. It is usually attached to the thunderstorm base and forms along the gust front.
SHELF CLOUD - Long, wedge-shaped clouds associated with the gust front. Shelf clouds indicate the downdraft or outflow of a thunderstorm.
Shelf cloud A low, wedge-shaped, and elongated cloud that occurs along a gust front; associated with and attached to a cumulonimbus cloud. ...
SHELF CLOUD - A type of accessory cloud associated with outflow regions of a thunderstorm. Commonly associated with gust fronts. Do not confuse these with wall clouds. Sometimes called a ROLL CLOUD.
Roll clouds, shelf clouds, and wall clouds are examples of accessory clouds.AccretionThe growth of a precipitation particle by the collision of a frozen particle with a supercooled liquid water droplet which freezes upon impact.
Sheet iceIce formed by the freezing of liquid precipitation or the freezing of melted solid precipitation (see snow depth)Shelf CloudA low, horizontal wedge-shaped arcus cloud, ...
arcus"(Often called roll or shelf cloud.) A dense and horizontal roll cloud or wedge-shaped accessory cloud, sometimes appearing ragged and turbulent and other times smooth, occasionally with multiple layers.
GUST-FRONT: The boundary between air flowing into a thunderstorm and the precipitation-cooled air flowing out of the storm. A shelf cloud may be seen above its surface position.
The leading edge of gusty surface winds from thunderstorm downdrafts; sometimes associated with a shelf cloud or roll cloud. See also downburst, gustnado, outflow boundary.
Gustnado ...
A cloud which is dependent on a larger cloud system for development and continuance. Roll clouds, shelf clouds, and wall clouds are examples of accessory clouds.
Accretion ...
Gust Front - The leading edge of gusty surface winds from thunderstorm downdrafts; sometimes associated with a shelf cloud or roll cloud. See also downburst, gustnado, outflow boundary.
Arcus - a low, horizontal cloud formation associated with the leading edge of the thunderstorm outflow (i.e., the gust front); roll clouds and shelf clouds both are types of arcus clouds ...
Roll clouds are relatively rare; they are completely detached from the thunderstorm base or other cloud features, thus differentiating them from the more familiar shelf clouds.
Gust Front: The leading boundary of relatively cold air flowing out of a thunderstorm, usually producing gusty winds, a noticeable wind shift and temperature drop when the gust-front passes (similar to a cold front). A shelf cloud may be seen ...
If two or more of these gust fronts intersect each other, a new thunderstorm could possibly develop. Sometimes it is associated with a shelf cloud or roll cloud. Also, see downburst, gustnado, and outflow boundary.
 See also: Cloud, Front, Gust Front, Storm, Thunderstorm
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