castellanus

Castellanus is a cloud morphology term used in the classification of clouds to describe a castle-like appearance of towers or turrets rising from the upper parts of a cloud mass. The term comes from Latin castellanus, meaning “of a castle.” It is applied as a species designation to several cloud genera, most commonly altocumulus castellanus, cirrus castellanus, cumulus castellanus, and stratocumulus castellanus.

In castellanus clouds, small vertical projections or turrets extend upward from the cloud base or along the upper margins, giving a crenellated or battlement-like edge. The turrets may be dispersed or clustered and can vary in length. This feature indicates that there is vertical air motion and instability within the cloud, with updrafts strong enough to lift portions of the cloud into higher levels of the atmosphere.

Weather significance and development: the presence of castellanus suggests convective potential and a tendency for the cloud to develop further, sometimes into cumulonimbus or towering cumulus. While not a guarantee of severe weather, castellanus clouds are commonly observed during developing convective situations and may be associated with showers or thunderstorms, especially if the turrets become more pronounced or widespread.

Observations of castellanus are included in standard cloud tallies and forecasts, helping forecasters gauge the likelihood of increasing vertical development and convective activity.