Cloud of the Day – Fall Streak Hole
A fall streak hole can appear in altocumulus or cirrocumulus cloud. It looks as if part of the cloud just fell out, leaving a hole. Often you can see streaks of ice crystals extending down below it. A fall streak hole is also known as a hole punch cloud, a skypunch or a cloud hole, among other names.
The hole is caused by the sudden freezing of super-cooled water in the cloud. Water can cool to well below freezing without forming droplets or crystals if there is no source of nucleation to allow it. The sudden introduction of a nucleation process sets off a domino effect, and the hole and fall streaks can form very rapidly. One source of nucleation is the disturbance caused by a passing aircraft.
Other than its association with the mentioned cloud types, a fall streak hole does not signify any particular kind of weather. Neither does it indicate that a UFO just punched through the cloud.
Tap pictures for large originals.