ROLL CLOUD

A roll cloud is a low, horizontal tube-shaped arcus cloud associated with a thunderstorm gust front, or sometimes a cold front. Roll clouds can also be a sign of possible microburst activity.Roll clouds are relatively rare; they differ from shelf clouds by being completely detached from the thunderstorm base or other cloud features. Roll clouds usually appear to be "rolling" about a horizontal axis.
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A low, horizontal tube-shaped arcus cloud associated with a thunderstorm gust front (or sometimes with a cold front ). 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 . Roll clouds usually appear to be "rolling" about a horizontal axis, but should not be confused with funnel clouds .