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A fallstreak 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.
Fallstreak hole in south eastern Ontario (over Ottawa), Canada. Photo by oneflightlessbird in r/CLOUDS, on Reddit, 8 May '26. "The holes are caused by supercooled water in the clouds suddenly evaporating or freezing..." - Wikipedia The photo went into Wikipedia on the same day, under Examples.
Some recent illustrations I’ve made for Reports From Unknown Places, my meteorological fiction project.
Hole Punch Cloud or Fallstreak Hole
August 17, 2008
Fallstreak Holes
Occasionally clouds appear to have a hole in them; these are known as fallstreak holes or hole-punch clouds. (Image credit: J. Stevens/NASA; via NASA Earth Observatory) Read the full article
Fallstreak hole
Shades of shiny red, orange, yellow and blue flooded the sky in Athens and Attica at dusk on Tuesday, February 2020. I was speaking on the phone with a friend and we were both watching from our windows how the threads of the shiny colors intermingled with the layers of thin clouds. “Aaaawesome! Look, it’s like embroidery!” I told my friend and she answered “God is embroidering the sky and is sending us a gift.” We kept chatting and stunning, not knowing that we were witnesses of a rare phenomenon called Fallstreak Hole.
The Fallstreak Hole with its impressive colorful cloud formation is a rare one.
According to the meteo.gr website of the National Observatory of Athens, this particular weather phenomenon requires some special conditions to happen.
A Fallstreak Hole (also known as hole punch cloud) is a large gap, usually circular or elliptical, that can appear in cirrocumulus or altocumulus clouds.
Clouds above the 5-6 km height in the troposphere, such as the uppers and turrets in the video, are mainly composed of water even if the temperature is very low, below -20 ° C.
The water in this state is supercooled and this is because there are no condensation cores (salt, carbon, silver iodide or other metals) to form regular drops or ice crystals (to form a raindrop or an ice crystal there is a need for a crystal surface ).
Such holes are formed when the water temperature in the clouds is below freezing, but the water, in a supercooled state, has not frozen yet due to the lack of ice nucleation.
The ice crystals find themselves surrounded by droplets, and grow quickly by the Bergeron process, causing the droplets to evaporate and creating a hole with brush-like streaks of ice crystals below it
Drops evaporate and the water vapor increases in size of the ice crystals until they grow large enough and begin to fall, as shown in the center of the hole.
Hole punch clouds - Fallstreak come in different Size and Shapes
Hole Punch Cloud and Fallstreak Time Lapse Video over Spokane, WA 2/18/15
