: a rounded mass of cumulus or cumulonimbus cloud often appearing before a thunderstorm.

Cumulonimbus (from Latin cumulus, “heaped” and nimbus, “rainstorm”) is a dense, towering vertical cloud, forming from water vapor carried by powerful upward air currents. If observed during a storm, these clouds may be referred to as thunderheads.

When the rising air cools, its water vapor condenses. The updrafts create tall cumulonimbus clouds. Winds blow the cloud top sideways. This makes the well-known anvil shape of a cloud known as a thunderhead (Figure below).

20,000 feet

n. cognizance, brightness, light, understanding.

Like all other types of clouds, stratocumulus clouds are condensed water droplets. They are formed when warm, moist air rises into the atmosphere. As air continues to rise, it cools. Since cool air cannot hold as much moisture as warm air, the water condenses onto tiny dust particles that are floating in the air.

The definitional difference between these two is the height at which they occur. Stratocumulus are low-level clouds that will have their bases below 6500 feet whereas Altocumulus cloud bases are between 6500 and 20,000 feet making them mid-level clouds.

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Low-level clouds (0-2 km): stratus, cumulus, cumulonimbus, and stratocumulus.

The true color of clouds is ‘none’. Clouds are composed of water vapor and unless illuminated by colored light, as in a sunset or sunrise, are colorless. Clouds appear dark when they are thick enough to decrease the amount of light they transmit.