What weather is present in Jupiter's great red spot?
You seem to know most of what there is to know about the Great Red Spot, except that there is not enough moisture in it for rain. It is cold enough for snow, but again there is a water deficiency. Water vapour is a comparatively rare gas in Jupiter's upper atmosphere. I think lightning would be admissible, and high winds too, and just possibly some frost. After all, there is frost on Mars despite the scarcity of water, though frost doesn't seem to be commonplace there.

The Great Red Spot would not be a good place for settlers, they'd be much better off on Mars. I presume this air base is carried around by a huge balloon, but what would they do for food and water? Normal aircraft would be no use because of the lack of oxygen, which is a pity, because there is hydrogen fuel in abundance.