Cirrocumulus castellanus
Cc cas
Cirrocumulus castellanus
© Wetterkurs.ch
Description
The name "castellanus" (Latin for castle-like, from castellum – small castle) describes clouds that display tower- or battlement-like protrusions rising from a common base. Cirrocumulus castellanus consists of small, turret-shaped elevations at high altitude, composed of ice crystals or supercooled water droplets. The individual turrets are wider than their common horizontal base, giving the cloud a characteristic battlemented appearance. This cloud form develops through convective instability in the upper troposphere, where locally confined updrafts produce the typical vertical protrusions. Cirrocumulus castellanus is a rather rare occurrence and is considered one of the most reliable indicators of instability at high altitudes.
Identification Features
- Small, tower-like protrusions rising from a common, narrow base
- The turrets are at least as wide as they are tall, often even wider than the horizontal base
- Occurs at high altitude (typically above 6,000 m), therefore appearing very small in the sky
- Whitish, delicate appearance, noticeably smaller than Altocumulus castellanus
- Individual elements have an apparent diameter of less than 1 degree (smaller than a little finger held at arm's length)
- Battlement- or crown-like silhouette when viewed against the light
- Can develop rapidly and dissolve again relatively quickly
- Frequently appear in rows or bands
Occurrence by genus
Highlighted: all genera with which castellanus occurs.
Meteorological Significance
Cirrocumulus castellanus is an important indicator of convective instability in the upper troposphere. Its appearance, especially in the morning, often points to the development of thunderstorms during the course of the day, as the instability at altitude indicates a general destabilization of the atmosphere. In combination with Altocumulus castellanus, this cloud form is considered a particularly reliable warning signal for imminent convective weather events. The cloud can also be a precursor to the approach of a cold front or an upper-level trough, which may lead to a deterioration of weather conditions in the following 12 to 24 hours.
Facts
- WMO-Code
- Cc cas
- Height layer
- High clouds
- Typical height
- 6.0 - 12.0 km
- Genus
- CIRROCUMULUS