Clouds

November 1, 1998

Clouds form when water vapor condenses on sea salt, dust, smoke particles, volcanic ash, or nitrous oxide formed by lightning, making drops 10^-6 the size of a raindrop. These tiny drops stick together more and more until they are big enough to drop. Fine raindrops come from low clouds, and big raindrops come from high clouds or thick clouds. 

The types of clouds are: 
	Cirrus:    white, feathery, 4-8 mile high clouds
	Cumulus: billowy, deep, fluffy, white, 1 mile high clouds
	Stratus:  flat, scattered, low or high, white or gray clouds
	Nimbus:  gray or dark clouds 

At a weather front, warm air rises and cools to make clouds and precipitation. 

A cold front first makes high and thick clouds {cumulonimbus clouds} and later dark, low clouds and small strong storms. A cold front can make a line of dark clouds {squall line}, from which can come funnel-shaped clouds with spinning air on land {tornado} or on the sea {waterspout}. 

A warm front first makes high thin clouds {cirrus clouds}, then wispy clouds {cirrostratus clouds}, then gray clouds {altostratus clouds}, then low, thick, dark clouds {nimbostratus clouds} with a broad area of light rain.