Cumulus clouds resemble light cotton; or are more commonly referred to as popcorn, the later being easily remembered. Their formation occurs at a relatively low altitude of 300 metres and continues to grow vertically, which gives them that rising mound appearance. The bases of these clouds are dark grey, while the sunlit tops are bright white, giving them the stereotypical cloud look.
The formation of cumulus clouds occurs when warmer air rises up into cooler air above it. During this process the moisture in the air parcel convects, and some water vapour condenses out, thus creating a cumulus cloud. It is known that the dimensions of the cloud strongly depend on the temperatures and any atmospheric inversion which may be present. Usually the base of the clouds appears at a height of about 2400 metres. However, in dry and mountainous places of the globe, cthe foumulus clouds' base can appear as high as 6000 metres; which means that cloud formation depends largely on the amount of moisture available to condense out.
Cumulus clouds could be an indication of when the atmosphere experiences some level of instability from the formation of strong upward air currents. The moisture infested air enriches the cloud, which can produce very powerful rain downpours, general storms, floods, and strong winds. When air currents increase in power, the atmosphere will become unstable, which will force the cumulus clouds to change into cumulonimbus clouds. Once formed these can potentially create supercell storms.
Cumulus clouds have that stereotypical popcorn look. Although there are many different types of these clouds, that can be classified under this term. They are
Cu congestus, these sharply outlined, tall clouds rise rapidly and may have their tops separated from the main cloud bodies due to strong wind sheer.
Cu humilis, have minimal vertical growth, that does not create a lot of atmospheric instability. These clouds have flat bottoms and are usually seen in small bunches.
Cu mediocris, where the top of the cloud does not have clear cut edges. These cloud formations create noticeable atmospheric instability which can result in showers or drizzle.
Cu radiatus, are arranged in straight and sometimes parallel bands that tend to meet over the horizon as observed by people. The spaces between the bands are in fact strong wind sheers.
Cu fractus, are unordered cumulus formations. These clouds appear ragged and torn.
All cumulus clouds are quite fragile and usually break up and disappear due to consistent and powerful winds. Once the clouds reach a height where water freezes, it precipitates snow or rain, depending on how cool the ground is, as this would allow snow flakes to reach it. Once the cloud precipitates out, it breaks up and disappears as well at times.