Altocumulus floccus
Ac flo
© Wetterkurs.ch
Description
The name "floccus" (Latin for tuft or flake) describes the fluffy, tufted appearance of this cloud species. Altocumulus floccus consists of small, swollen cloud towerlets with ragged, fibrous bases that frequently exhibit virga (fallstreaks). The individual cloud elements resemble small, tattered cotton wool tufts, whose bases dissolve rapidly while the tops billow upward in a cauliflower-like manner. This cloud form develops through convection in the middle troposphere, where unstable air layers are locally moist enough to generate limited updrafts and condensation. Altocumulus floccus frequently appears in groups or bands and is an important indicator of instability at mid-levels.
Identification Features
- Small, fluffy cloud towerlets with swollen, rounded tops
- Ragged, dissolving bases, often with fallstreaks (virga)
- Individual elements resemble small, tattered tufts or cotton wool puffs
- Frequently appear in groups, rows, or irregular fields
- Noticeably smaller than cumulus clouds, but larger than cirrocumulus elements
- Typically found at altitudes between 2,000 and 6,000 metres
- The base of individual tufts is often poorly defined or entirely absent
- Often visible in the sky alongside other altocumulus species
Occurrence by genus
Highlighted: all genera with which floccus occurs.
Meteorological Significance
Altocumulus floccus is a significant indicator of increasing instability in the middle troposphere. Its appearance, particularly in the morning, frequently signals the development of thunderstorms during the course of the day, as it points to the availability of moisture and buoyancy at mid-levels. In combination with altocumulus castellanus, it is considered one of the most reliable precursors of afternoon convective activity. When persistent, it can indicate an approaching disturbance or front bringing showers or thunderstorms. In aviation meteorology, altocumulus floccus is given particular attention, as the associated instability can cause turbulence at mid-level flight altitudes.
Facts
- WMO-Code
- Ac flo
- Height layer
- Mid-level clouds
- Typical height
- 2.0 - 6.0 km
- Genus
- ALTOCUMULUS