Fallstreak hole
| Fallstreak hole (Cavum) | |
|---|---|
Fallstreak hole over Austria | |
| Abbreviation | cav |
| Genus | Cirrocumulus, altocumulus, stratocumulus |
| Variety | Supplementary feature |
| Altitude | 500–15,000 m (2,000–49,000 ft) |
| Appearance | Hole in the clouds |
| Precipitation | Virga |
A fallstreak hole – also known as a cavum, hole punch cloud, punch hole cloud, skypunch, cloud canal, or cloud hole – is a large gap, usually circular or elliptical, that can appear in cirrocumulus or altocumulus clouds. The holes are caused by supercooled water in the clouds suddenly evaporating or freezing, and may be triggered by passing aircraft. Such clouds are not unique to any one geographic area and have been photographed from many places.
Due to their rarity and unusual appearance, fallstreak holes have been mistaken for or attributed to unidentified flying objects.