Cumulus congestus

Cumulus Congestus are Cumulus with great vertical development, whose tops have protruding edges, indicating strong rises (but not yet showing fringes and fibers). They indicate a thicker moist layer than Cumulus humilis. Its existence indicates deep layers of instability and favoring cyclonic runoff at altitude; may have important implications for the development of Cumulonimbus.

These are characteristics of unstable regions of the environment that are undergoing convection. They are often characterized by sharp contours and large vertical development. Because Cumulus congestus are produced by strong upward air currents, they are usually taller than wide, and their tops can reach 6 km or more (in the tropics).

Generally Cumulus congestus are formed by the development of Cumulus mediocris, but they can also be formed from Altocumulus castellanus or Stratocumulus castellanus. Cumulus congestus can evolve to Cumulonimbus calvus under sufficiently unstable conditions. This transformation can be seen by the presence of a smooth, fibrous or striated appearance top. This type of cloud produces precipitation, often in abundance.

For a Cumulus mediocris to evolve into a Cumulus congestus, air needs to become more unstable and humid and convection to increase (by additional surface heating, orographic elevation or the arrival of a cold front), and can then grow vertically as over the course of a day turning into large, isolated clouds forming cauliflower-like mounds, domes, or towers (the Cumulus congestus). If a Cumulus congestus continues to grow vertically, it will become a Cumulonimbus.

Cumulus congestus are blown away and then disappear more or less quickly, sometimes producing virga (when water droplets can no longer sustain themselves and fall into a comma shape, evaporating before reaching the ground). They are Cumulus in the last stage of development before Cumulonimbus.