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❋ Fallstreak Holes & Fallstreak Canals ❋
⮚ Click me for the footage collection! 🤪 ⮘
Collection of Fallstreak Phenomenon Pictures
And yes I have a gif here because I don't know where else to put it lmao, so shush.
Here's also a video timelapse of fallstreak canals and holes forming:
A fallstreak hole or a fallstreak canal, also known to many as a cavum, a hole punch cloud, a punch hole cloud, a skypunch, a cloud canal or a cloud hole, is a large gap, usually circular or elliptical that typically occur in cirrocumulus or altocumulus clouds.
Their formation is relatively straightfoward:
The air surrounding a given swath of cloud is below freezing, supercooling the suspended water dropets, but not freezing them, due to the lack of material to crystalize on. Everything is well until a disturbance occurs, triggering spontaneous freezing due to the Wegener–Bergeron–Findeisen process.
Terminology - the Wegener–Bergeron–Findeisen process: The process by which precipitation is initiated in a mixed cloud with a temperature below freezing. Because the equilibrium vapour pressure of water vapour with respect to ice is less than that with respect to liquid water, ice crystals grow at the expense of supercooled water droplets. Eventually the crystals become sufficiently heavy to begin to fall, and may subsequently be modified by other processes such as accretion, melting, coalescence, and evaporation. The theory was introduced by Bergeron in 1933 and subsequently extended by W. Findeisen.
As more and more water vapour is drawn into the "domino effect", it eventually will create a usually circular hole in the clouds, though sometimes these "holes" can be large and/or long.
This effect can be more clearly seen via this demonstration below:
Usually, the disturbance is caused by a passing aircraft or of the like, as the low pressure created behind the propeller of said craft cools the air even more, forming ice crystals in which other water molecules and nucleate onto.
Due to their unusual appearance and apparent rarity, some people attribute sightings to UFOs 🤷♂️.