Altocumulus

Altocumulus is a mid-level cloud genus composed of rounded, white to gray cloud elements that often form in patches or sheets. It typically occurs at altitudes of about 2,000 to 7,000 meters (6,500 to 23,000 feet), placing it in the middle portion of the troposphere. Altocumulus elements may appear as individual clumps or as a continuous layer, and they frequently create patterns that resemble a field of rounded puffs or a mackerel sky when seen at a distance.

The appearance of altocumulus varies by form. Common manifestations include stratiformis, a layered or sheet-like arrangement; lenticularis, lens-shaped clouds that can be aligned in lines; and castellanus, which show small towers suggesting vertical development. The undulatus form produces rippled, wave-like patterns. Altocumulus can be white or light gray and often shows shading between the cloud elements, with gaps of clear sky visible in some patterns.

Formation and weather implications differ with the level of atmospheric instability. Altocumulus generally forms where mid-level air is rising or becoming unstable, and it can indicate changing weather conditions within the next 24 hours. When associated with stronger vertical development, such as altocumulus castellanus, there is a greater potential for convective activity and, in warm seasons, possible thunderstorm development later in the day. In most cases, altocumulus does not produce heavy precipitation, though thickened or dense patches can yield light rain or drizzle, particularly if they thicken into lower or more extensive cloud layers. Altocumulus differs from higher cirrus and lower cumulus by its mid-tropospheric altitude and cloud structure.