Why do puffy little clouds cause turbulence?

I get the problem with flying through cumulo-nimbus clouds. They contain major updrafts and down drafts - huge blasts of air that would really blast a plane flying through. But why is there turbulence - minor but certainly obvious - when a plane flies through what amounts to a small puff of fog? Virtually any little cloud will cause a noticeable bump in the flight. Extremely slight differences in temperature or density seem to be the only explanation I can think of, but that seems so minor to be able to change the course of a flight (ever so slightly) of a big heavy craft. Dopers?

the clouds don’t cause turbulence, the updrafts that cause the clouds to form do.

And, clouds result when there is a difference in humidity between the two air masses. There can be plenty of turbulence at the interface of two orthogonal air streams of similar moisture content.


Right - and those updrafts continue into the clouds itself, even when it’s no more than a small puff of fog.

One man’s turbulence is another man’s lift. As a glider pilot, I love seeing those puffy white clouds. They mark the thermals I need to get around. But, if there is air going up there must be air coming down somewhere around, often immediately adjacent to the thermal. I can be cruising along and suddenly be in sinking air and just as suddenly be in air that is going up as fast or faster than the air that is going down (faster because thermals are fairly narrow and areas of sink much larger). It can be a real kick in the butt when you hit a boomer. Pilots of small planes don’t like flying through thermals - it can be pretty bumpy. Glider pilots don’t like flying through them either - we like to fly IN them. “Going up?” “Yes, thank you!”

What is the relationship between the size and location of a “little puffy cloud” and the size and location of a thermal? I think of thermals as toroids. Are they simply rising air? Are there thermals inside of a cloud? around a cloud?

I took glider flying lessons, many years ago when the world and I were much younger. Here’s another relevant lesson about thermals and puffy white clouds, which my CFI demonstrated to me one day: You can fly your glider up the thermal until you reach the base of the cloud, and continue to go right into the bottom of the cloud. This, in fact, is ill-advised. Clouds, as seen from the inside, are amazingly opaque. While inside a cloud, you are flying blind.

Now, given the routine instruments in a glider and just a wee bit of flying skill, this should be easily survivable. But where I took lessons, we were also in the vicinity of major international airports (San Francisco and Oakland), so one always had to worry about getting sucked, like a goose, into a passing jet engine in the dark.

Almost. A thermal is a rising vertical pillar of air, warmer than the surrounding air, above a hot area on the ground (like a plowed field or parking lot in the sun). As it rises, it gets cooler. At some point, the moisture condenses, causing a cloud. Thus, the picture is a pillar with a cloud sitting at the top of it.

ETA: The rising pillar continues on up into the cloud. The condensation temperature tends to remain at a particular altitude, so the bottom of the cloud stays in one place rather than rising with the thermal itself, and the bottom of the cloud tends to be fairly flat. But the rising air (now with condensation) continues up into the cloud, causing the puffy appearance. That’s why these sorts of clouds are flat on the bottom and puffy and billowy on the top.

If they are really small puffy clouds they are called “flak.”

I think you can figure out the turbulence for yourself. :smiley: