Castellanus

A castellanus (or castellatus) (from Latin castellanus, castle) is a cloud that displays at least in its upper part cumuliform protuberances having the shape of turrets that give a crenellated aspect. Some of these turrets are higher than they are wide; they have a common base and seem to be arranged in a line. The castellanus characteristic is particularly obvious when the clouds are observed from the side (i.e., from a vantage point on a line perpendicular to the line of orientation).

It is a cloud species attached to the cloud genera cirrus, cirrocumulus, altocumulus and stratocumulus. Species of the clouds include cirrus castellanus, cirrocumulus castellanus, altocumulus castellanus and stratocumulus castellanus. Sometimes cumulus castellanus are referred to, but the type is not recognised by France's national meteorological service Météo-France, or by the American Meteorological Society and World Meteorological Organisation. Those clouds some would classify as cumulus castellanus typically do not have a common base and are not arranged in a line, thus differing to some extent from the more universally-recognised castellanus types. Some scientists also think that the castellanus should be a full cloud genus, and not just a cloud species. The Federal Aviation Administration implicitly considers a castellanus as a full cloud genus.