Pileus (meteorology)

A pileus is like a hat that clouds wear sometimes. When warm and moist air rises, it cools down and forms clouds called cumulus clouds. Sometimes, when the cumulus cloud is growing really fast, it can create a pileus cloud on top of it.

Think of it like making a tower out of blocks. You start building and building, and suddenly it gets really tall. But, while you're building it, someone puts a hat on top of it. That's kind of what happens with a pileus cloud.

This pileus cloud looks like a smooth, flat disk that sits on top of the cumulus cloud. It happens when the warm air that is rising hits a layer of colder air. The cold air is warmer than the top of the cumulus cloud, so the warm air from the cloud rises really fast, creating a little gap behind it.

Then, the colder air rushes in to fill that gap, and since it is colder, it can't hold as much water vapor as the warm air. This makes the water vapor in the air condense and form a cloud, which becomes the pileus cloud.

So, the next time you see a big fluffy cloud with a smooth, flat hat on top, you can say, "Hey, that's a pileus cloud!"