Altocumulus lacunosus
Ac la
Altocumulus lacunosus
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Description
The name "lacunosus" (Latin: full of holes, from lacuna = gap, hollow) describes a cloud layer perforated by numerous rounded gaps or holes, creating a net-like or honeycomb pattern. Altocumulus lacunosus is a relatively rare variety in which the cloud layer appears like a perforated sheet of fabric. The holes are mostly rounded to irregularly shaped and surrounded by ragged cloud edges. This appearance is caused by localized sinking motions of the air (convection cells) arranged in a regular pattern. The structure is reminiscent of a honeycomb and is sometimes also compared to a fishing net.
Identification Features
- Cloud layer with numerous rounded holes or gaps forming a net-like or honeycomb pattern
- The gaps are often more regularly arranged than in other broken cloud forms
- The edges of the holes frequently appear ragged or curved downward
- The cloud is found at mid-level altitudes, typically between 2,000 and 6,000 meters
- The pattern resembles a sieve or honeycomb structure
- Not to be confused with Altocumulus perlucidus, in which the gaps are less regular and less pronounced
- The holes can vary in size, but tend to be fairly uniform within a given field
Occurrence by genus
Highlighted: all genera with which lacunosus occurs.
Meteorological Significance
Altocumulus lacunosus is a rather rare cloud phenomenon and indicates instability in the mid-troposphere. The characteristic holes are formed by organized convection cells with descending air in the gaps. The appearance of this cloud form can indicate a change in air mass structure and sometimes precedes a deterioration in weather conditions, though it is not a reliable indicator of any particular weather development. The phenomenon is often short-lived, as the patterns can be rapidly broken up by wind shear and turbulence.
Facts
- WMO-Code
- Ac la
- Height layer
- Mid-level clouds
- Typical height
- 2.0 - 6.0 km
- Genus
- ALTOCUMULUS