Are a type of cumulus cloud associated with thunder storms and heavy precipitation. They are also a variation of nimbus or precipitation bearing clouds.They are formed beneath 20,000 ft. and are relatively close to the ground.
Cumulonimbus is a heavy and dense cloud of considerable vertical extent in the form of a mountain or huge tower, often associated with heavy precipitation, lightning and thunder. The mature Cumulonimbus cloud has a distinctive flat, anvil shaped top.  Cumulonimbus clouds are thunderstorm clouds. High winds can flatten the top of the cloud into an anvil-like shape. Cumulonimbus clouds are associated with heavy rain, snow, hail, lightning and even tornadoes. The anvil usually points in the direction the storm is moving. Top 10 facts about the world. A cumulonimbus cloud is one of the largest clouds formed in Earth's weather patterns. The tall, column-like appearance, often with a flat top, can indicate severe lightning, heavy rain and high winds. A super cell thunderstorm is a mature cumulonimbus cloud with internal rotation, called a mesocyclone. Air moving in different directions at different altitudes causes the super cell to rotate, which can cause tornadoes or severe winds. Cumulus clouds are often precursors of other types of cloud, such as cumulonimbus, when influenced by weather factors such as instability, moisture, and temperature gradient. Normally, cumulus clouds produce little or no precipitation, but they can grow into the precipitation-bearing congestus or cumulonimbus clouds.  Cumulonimbus, from the Latin cumulus (heap) and nimbus (rainstorm, storm cloud), is a dense towering vertical cloud associated with thunderstorms and atmospheric instability, forming from water vapor carried by powerful upward air currents. The cumulonimbus base may extend several miles across and occupy low to middle altitudes-formed at altitude from approximately 200 to 4,000 m (700 to 10,000 ft). The pyrocumulonimbus cloud (pyroCb) is a type of cumulonimbus cloud that forms above a source of heat, such as a wildfire, and may sometimes even extinguish the fire that formed it.  Cumulonimbus clouds belong to the Clouds with Vertical Growth group. They are generally known as thunderstorm clouds. A cumulonimbus cloud can grow up to 10km high. At this height, high winds will flatten the top of the cloud out into an anvil-like shape. Cumulonimbus clouds are associated with heavy rain, snow, hail, lightning, and tornadoes. Cumulonimbus can form alone, in clusters, or along cold front squall lines. These clouds are capable of producing lightning and other dangerous severe weather, such as tornadoes. Cumulonimbus progress from overdeveloped cumulus congestus clouds and may further develop as part of a supercell. The cumulonimbus base may extend several miles across and occupy low to middle altitudes-formed at altitude from approximately 200 to 4,000 m (700 to 10,000 ft). Cumulonimbus clouds. Credit: NASA. Cumulonimbus clouds are a type of cumulus cloud associated with thunder storms and heavy precipitation. They are also a variation of nimbus or precipitation bearing clouds. They are formed beneath 20,000 ft. and are relatively close to the ground. This is why they have so much moisture. Cumulonimbus clouds form in the lower part of the troposphere, the layer of the atmosphere closest to the surface of the Earth. This region due to evaporation and the greenhouse effect produces alot of the warm updrafts that make creation of cumulus and cumulonimbus clouds possible. Mature cumulonimbus clouds are typically called thunderstorms. Lightning occurs as electrical energy is produced from the friction of water in the cloud. A column-like towering cloud forms with a flat top shape, often called an anvil. A super cell thunderstorm is a mature cumulonimbus cloud with internal rotation, called a mesocyclone. Air moving in different directions at different altitudes causes the super cell to rotate, which can cause tornadoes or severe winds.
http://www.skybrary.aero/index.php/Cumulonimbus http://www.weatherwizkids.com/weather-clouds.htm http://www.wisegeek.com/what-is-a-cumulonimbus-cloud.htm https://en.wikipedia.org/wiki/Cumulus_cloud https://en.wikipedia.org/wiki/Cumulonimbus_cloud https://en.wikipedia.org/wiki/Pyrocumulonimbus_cloud http://www.windows2universe.org/earth/Atmosphere/clouds/cumulonimbus.html https://en.wikipedia.org/wiki/Cumulonimbus_cloud http://www.universetoday.com/41646/cumulonimbus-cloud/ http://www.wisegeek.com/what-is-a-cumulonimbus-cloud.htm
what is a cumulonimbus cloud?