JJoosseelllleMM aaeYY .MM aanniittii MMrrss.SS hhaarroonDD aavviidd IIV–DD eJJ eessuu ss SScciieennccee Kinds of Clouds Cumulus clouds are white, puffy clouds that look like pieces of floating cotton. u!ulus clouds are often called "fair#weather clouds". $he %ase of each cloud is flat and the top of each cloud has rounded towers. &hen the top of the cu!ulus clouds rese!%le the head of a cauliflower, it is called cu!ulus congestus or towering cu!ulus. $hese clouds grow upward and they can develop into giant cu!uloni!%us clouds, which are thunderstor! clouds. 'n arcus cloud is a low, hori(ontal cloud for!ation. )oll clouds and shelf clouds are the two types of arcus clouds. ' shelf cloud is usually associated with the leading edge of thunderstor! outflow* roll clouds are usually for!ed %y outflows of cold air fro! sea %ree(es or cold fronts in the a%sence of thunderstor!s. Stratus clouds are unifor! grayish clouds that often cover the entire sky. $hey rese!%le fog that doesn+t reach the ground. ight !ist or dri((le so!eti!es falls out of these clouds. '' nimbus cloud is a cloud that produces precipitation. -sually the precipitation reaches the ground as rain,, hail,, snow, or sleet.. alling precipitation !ay evaporate as virga. )ain co!es out of ni!%us clouds and this is called precipitation. Since ni!%us clouds are dense with water, they appear darker than other clouds. /i!%us clouds are for!ed at low altitudes and are typically spread unifor!ly across the sky. .