Banner clouds can form on the side of a high or exposed peak and seem to stick to the mountain face like a banner, even on an otherwise cloudless day. There are several theories for how they form but in general strong winds of cold dry air from one side likely interact with warmer humid air on the other. Look out for them next time you're in the mountains.

Also see lenticular clouds, thunder clouds, and more clouds.

Banner cloud

Apophenia is finding meaning and connections in unrelated things.

This might be faces in pieces of toast, or the man in the moon, or clouds making incredible shapes. Seeking patterns and meaning in random data is something we seem naturally inclined to do.

Also see: narrative bias — how stories feel better than randomness.

Apophenia

Nature’s greatest snow machine, where crazy amounts of snow can fall in huge snowstorms on the downwind — leeward — side of a lake. Where the effect is pronounced, such as on the East of some of the Great Lakes in the US, it can generate regions known as snow belts because of the amount of snow they receive.

It works kind of like this: cold air blows over a lake. As the cold air passes over the warmer lake it picks up water vapour from the lake and it warms. This causes it to rise and in turn cool, such that when it reaches the downwind side of the lake it is now a lot of cold moist air which can cause some incredible snowstorms, like 2–3 inches of snow per hour. Satellite pictures like these show it in action pretty clearly.

If the land rises after the lake, the air can cool faster and increase the effect — and also cause a rain shadow — and if there’s a whole lot of convection and the air is rising fast, you can get what’s called thundersnow — a thunderstorm in a snowstorm. I know.

Find the weather interesting? Me too. Also see:

Yesterday’s weather (applying weather forecasting to productivity forecasting)

Know your cirrostratus from your altocumulus

Lake-effect snow

A dirty thunderstorm is caused by ash and rock interacting inside a cloud instead of ice particles.

As you can imagine, you can get this with volcanoes, which can be pretty spectacular.

See more about how lightning forms inside a thunder cloud.

Dirty thunderstorm

Thunder clouds are so impressive. Lightning forms due to air currents in the cloud as warm moist air rises up quickly. All the collisions between particles cause different charges to develop between the top and the bottom of the cloud. When that gets large enough, kapow!

Also see: thunderclap or rumble, dirty thunderstorms.

Thunder clouds

Make spectacular photos like these, these, or this, but generally mean high winds high up. Look out.

Lenticular clouds

Stratus: layers AND Cumulus: heaps + height + Cirrus at the very top and you’re a long way already.

Clouds sketches