4 December 2014
This “Hole Punch Cloud” was spotted over Somerset County Maryland today, and the technical name meteorologists use is “Fall Streak Hole”. They are rather rare, and happen when super-cooled water in a cloud suddenly freezes. The freezing can be started by the introduction of some ice crystals and then the super-cooled water freezes, and falls out as ice crystals. Liquid water at temperatures well below freezing is actually fairly common in the atmosphere, and it doesn’t take much to make it suddenly freeze into ice crystals. It is thought that ice crystals caused by aircraft are often what cause these to form.
You can see the strange behavior of super-cooled water in several videos on YouTube here.
The actual process here is a bit complex, but you can read more about this phenomenon here. For those who want a more technical view, the latest science about them is in this paper in Science. It is just old enough that it should be free to view, even if you do not subscribe.
UPDATE- More info on new research on these is here: http://www2.ucar.edu/atmosnews/news/2185/mysterious-clouds-produced-when-aircraft-inadvertently-cause-rain-or-snow