Just observed several cumulus “cloud streets” over Port Phillip Bay, running north/south, cloud base at about 2,000 feet, length of “cloud streets” about 1 mile long, presumeably this would provide lift for any gliders flying below them? I have in the summer months seen “cloud streets” running east/west right across the Bay, so can cloud streets form over open oceans?

bob(from black rock) said:

Just observed several cumulus “cloud streets” over Port Phillip Bay, running north/south, cloud base at about 2,000 feet, length of “cloud streets” about 1 mile long, presumeably this would provide lift for any gliders flying below them? I have in the summer months seen “cloud streets” running east/west right across the Bay, so can cloud streets form over open oceans?

You’ll usually see “cloud streets” over land beside the ocean, because of the way they’re formed. Warm air moving of the sea collects water vapour, then is heated by land it moves onto. The extra heat makes it lighter than surrounding air, which lifts it. Adiabatic cooling then causes the water vapour to condense, forming bands of cloud. If you watch, you’ll usually see them dissipate over about half an hour. This type of cloud can’t form over the ocean because it needs the extra heat of land (the same heat that causes afternoon breezes.) Glider pilots can use it, but it’s not particularly long-lasting.

The streets I saw yesterday were about a mile off shore, and another lot about a mile further out still, running parallel to the shore, there was no appreciable on,(or off) shore breeze.