Society member David Benn recently came across this article on the Science Daily website.
Mysterious clouds are produced when aircraft inadvertently cause rain and snow. This cloud ‘seeding’ is caused when the aircraft climbs or descends in certain atmospheric conditions and causes narrow bands of rain or snow to form.
This phenomenom has triggered speculation and wonder whenever the blue-sky holes have been sighted, even as far back as the 1940s.
The full article can be found here and is well worth a read!
There are also some very good photographs of hole punched clouds here – thanks to Glenys Chew for this link.