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| Cumulus Cloud | |
 Puffy cumulus illuminated by late afternoon sun far below a NOAA P-3 returning to base after a mission. |
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| Abbreviation | Cu |
|---|---|
| Genus | Cumul (heap) |
| Altitude | Below 2,000 m (Below 6,500 ft) |
| Classification | Family C (Low-level) |
| Precipitation cloud? | Depends. Cumulus humilis and mediocris, most likely no, but congestus, sometimes yes. Cumulonimbus, yes, but may be virga. |
A Cumulus cloud is a type of cloud with noticeable vertical development and clearly defined edges. Often described as "puffy" or "cotton-like" in appearance, cumulus clouds may be solitary, in lines, or in clusters. Cumulus clouds are often precursors of other types of clouds, such as cumulonimbus, when influenced by weather factors such as instability, moisture, and temperature gradient. They are often associated with phenomena such as dust devils, landspouts, waterspouts and tornadoes. Cumulus means 'heap' or 'a pile' in Latin.
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Formation
Cumulus clouds typically form when warmer air rises and reaches a level of comparatively cool air, where the moisture in the air condenses. This is usually through convection, where a parcel of air is warmer than the surrounding air. As it rises, the air cools at the dry adiabatic lapse rate (approximately 3°C per 1000ft or 1°C per 100m), while the dewpoint of the air falls by 0.5°C per 1000ft. When the temperature of the air reaches the dewpoint, some water condenses out of the air to form the cloud. The size of the cloud depends on the temperature profile of the atmosphere and the presence of any inversion. If the top of the cumulus cloud reaches above the freezing level in the atmosphere, then rain from the cloud is possible. If the top of the cloud is below freezing level, then snow is possible.
In windy conditions, the clouds can form lines (cloud streets) parallel with the wind. In mountainous areas, they can also form lines across the wind due to the presence of lee waves above the clouds.
Over the sea, cumulus clouds may be found in regularly spaced lines. The best examples of these lines are found in the trade winds where they extend for many miles. These lines create a pattern in the vertical movement of air, causing it to roll horizontally. Between the lines of cloud are stronger, more gusty, and slightly veering winds; but beneath the lines of cloud, somewhat lighter and more backing winds prevail.
The height at which the cloud starts to form (cloud base), depends on the amount of moisture in the air parcel that forms the cloud. In temperate areas, the base of the cumulus clouds is usually around 8,000ft (2,400m) in altitude. In arid and mountainous areas, the cloudbase can be in excess of 20,000ft (6,000m).
Glider pilots often use cumulus clouds, as they can be good indicators of rising air drafts or thermal underneath.citation needed
Forcast
Cumulus clouds often mean fair weather. These types of cumulus clouds often appear like small to medium sized puffy balls in the sky. However, some cumulus clouds can grow into cumulonimbus clouds which may produce heavy rain, lightning, severe and strong winds, hail, and even tornadoes. The towering cumulus clouds that appear like thin towers are the ones that often grow into cumulonimbus storm clouds. These tall towering clouds real name is cumulus congestes.
References
1. http://schoolscience.rice.edu/duker/weatypeclouds.html
See also
External links
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