Cloud of the Day – Pileus
A pileus cloud is one that forms on top of another cloud, forming a cap. The term pileus comes from the Latin for felt cap, of the sort worn in ancient Greece and Rome. Pileus cloud is most commonly seen on vigorously growing towering cumulus, and is indicative of instability and high moisture content. The term also refers to the cap of a mushroom, the bell of a jellyfish, and the top of a bird’s head. That is the reason for the name of the pileated woodpecker, referring to its ornamented head.
Pileus are lenticular clouds and share traits with altocumulus lenticularis in their smooth, horizontal appearance. In addition to towering cumulus, they can form on volcanic eruptions, smoke towering over forest fires, and nuclear mushroom clouds.
Due to high moisture and instability, pileus can be a sign of violent weather to come.
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