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Clouds roll through as weather delays the start of the Honor Roll track meet, Tuesday, May 28, 2024, at Waverly High School. The meet was eventually canceled. A long, tubular cloud that appears to ...
Altocumulus (from Latin altus 'high' and cumulus 'heaped') [1] is a middle-altitude cloud genus that belongs mainly to the stratocumuliform physical category, characterized by globular masses or rolls in layers or patches – the individual elements being larger and darker than those of cirrocumulus and smaller than those of stratocumulus. [2]
When these high clouds progressively invade the sky and the barometric pressure begins to fall, precipitation associated with the disturbance is likely about 6 to 12 hours away. A thickening and lowering of cirrocumulus into middle-étage altostratus or altocumulus is a good sign that the warm front or low front has moved closer and it may ...
Illinois averages around 50 days of thunderstorm activity a year which put it somewhat above average for number of thunderstorm days for the United States. Illinois is vulnerable to tornadoes with an average of 54 occurring annually, which puts much of the state at around 9.7 tornadoes per 10,000 square miles (30,000 km 2) annually.
The altocumulus undulatus is a mid-level cloud (about 8,000–20,000 ft or 2,400–6,100 m), usually white or grey with layers or patches containing undulations that resemble "waves" or "ripples" in water.
Mid-level stratocumuliform clouds of the genus altocumulus are not always associated with a weather front but can still bring precipitation, usually in the form of virga which does not reach the ground. Layered forms of altocumulus are generally an indicator of limited convective instability, and are therefore mainly stratocumuliform in structure.
The base of the cloud can form as low as 2,000 metres (6,500 feet), or as high as 6,000 metres (20,000 feet). They are very similar to cumulus congestus clouds, but at a higher level and with the cloud heaps joined at the base. Castellanus clouds are evidence of mid-atmospheric instability and a high mid-altitude lapse rate. [2]
In the middle level are the alto- clouds, which consist of the limited-convective stratocumuliform cloud altocumulus and the stratiform cloud altostratus. Mid-level clouds form from 2,000 metres (6,600 ft) to 7,000 metres (23,000 ft) in polar areas, 7,000 metres (23,000 ft) in temperate areas, and 7,600 metres (24,900 ft) in tropical areas.