A high, whispy cirrus cloud that descended and spread into a sheet was named cirrostratus, while groups of fluffy cumulus clouds that joined up and spread were named stratocumulus.
Storms that were strong enough to make these features--called above anvil cirrus plumes, or AACPs-- were also more likely to have severe tornadoes, large hail, and high winds.
In fact, all clouds belong to one of three principle types to which Howard gave the names: cirrus, Latin for tendril or hair, cumulus, heap or pile, and stratus, layer or sheet.
His tail floats now behind him, now above him, level or gracefully curled like a wisp of cirrus cloud, every hair in its place, clean and shining and radiant as thistle-down in spite of rough, gummy work.