Castellanus

A castellanus (from Latin castellanus 'castle'), or castellatus, 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.^[1] 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.^[1][2][3] Species of the clouds include cirrus castellanus, cirrocumulus castellanus, altocumulus castellanus and stratocumulus castellanus.^[1] 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.^[4] 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.^[5]