Cumulonnimbus clouds are clouds of vertical development. These clouds are found in weather like hail, strong winds and thunder storms. They can go up to 6,000 meters from the grown or maybe even bigger. The flat top, also known as the “anvil top” is white but the base is not. When these clouds are in a line it is called a squall line. Most of cumulonimbus clouds are made of water droplets and as you go up to the top, it get colder. Some may be formed by ice crystals though. When the clouds are cumulus, they may form into cumulonimbus clouds.

 

Sources:

Information- “Cumulonimbus Clouds reaching high into the atmosphere.” ww2010.atmos.uiuc.edu 2008 1-1. WW2010 University of Illinois. October 5, 2008.  http://ww2010.atmos.uiuc.edu/ .

Picture- Cumulonimbus Cloud. [Online Image] Oct 5, 2008 <http://pangea.tec.selu.edu/>.