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

Lake Effect Snow is a phenomenon where crazy amounts of snow can fall in massive storms on a lake’s downwind—leeward—side. Where the effect is pronounced, to the east of some of the Great Lakes in the U.S. (think Buffalo), it’s responsible for the regions known as the snow belt.

It works like this: Cold air blows over a lake. As the cold air passes over the warmer lake, it picks up water vapor from the water, which warms the air. This causes the air to rise and, in turn, cool, such that when it reaches the downwind side of the lake, it has become cold and moist. This simple change can lead to some incredible snowstorms dumping 2 to 3 inches of snow per hour. Satellite pictures show it in action pretty clearly.

If there is a rise in land elevation along the path of the cold air, the air can cool faster and increase the effect — and also cause a rain shadow. And if there’s a lot of convection and the air rises quickly, you can even get what’s called thundersnow—a thunderstorm in a snowstorm.

Find the weather interesting? Me too. Also see:

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

Know your cirrostratus from your altocumulus

For everyday weather-related phenomena explained, see Dennis Mersereau’s The Skies Above: Storm Clouds, Blood Moons, and Other Everyday Phenomena, Mountaineers Books (2022). Dennis is also the source of the lovely phrase Nature’s greatest snow machine.

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