A couple of weeks ago I had a nice local flight of a couple of hours. The day wasn’t good enough for me to go cross-country, due to big blue gaps in the sky like this:
Why do these matter to glider pilots? To stay aloft, we rely on thermals, rising columns of air. There were some epic thermals on this particular weekend. At times the air was rising at 4 meters per second and taking my glider with it. But there were also big gaps, and in general the sky was a bit of a mess, so most of us stayed at home like cowards.
On that subject, what sort of clouds are good?
In a thermal, the rising air gets colder, and eventually can’t maintain the water in its gaseous (vapour) form. It condenses to make a cloud, typically at a specific height, which is why these clouds all have flat bottoms:
But a strong thermal will continue upwards, and you’ll see a fluffy cauliflower top too.
So this cloud is probably rubbish:
but this cloud is probably great.
Unfortunately, you can’t see the top of the cloud when you’re right below it, so part of the fun is planning ahead to try to think where the next great thermal might be. That was quite difficult on my flight, so I’m glad I chickened out and stayed at home.
