Signs of a change in the weather

I'm a bit of a cloud geek, being Member No. 2812 of the Cloud Appreciation Society, so when I spotted a pileus cloud through my window this morning, I rushed to put on some clothes and grab the camera. Clouds boil up so fast, you have to be quick, and I wasn't quick enough, but I did get this.

The cumulus tower on the left did have a cloud cap, or pileus cloud, before it rose up and absorbed the layer of frozen fog.

The cumulus cloud on the right has a pileus cloud that's not so clearly defined, as it's in the process of changing, but if you look closely you can see its wispy wig, a sort of cloud comb-over, formed by the rapid condensation of moist air that's been pushed up over the summit of the cumulus cloud, where it freezes into ice crystals.

Pileus clouds signal a change in the weather. Within half an hour, the sky was full of ominous-looking clouds. The weather forecast said "snow".

Sometimes, snow arrives in a more dramatic fashion, like this enormous cumulonibus incus that brought snow over the North Sea last year - the photo is from my cloud journal.