Natalie Keller Reinert looked up to an unusual sight Friday morning in the Central Florida sky. The clouds above her appeared to have holes in them.
What were the bizarre disappearing clouds? They’re known as “fallstreak holes,” or more commonly “hole punch clouds.”
They typically form on stable days, when a blanket of altocumulus or cirrocumulus clouds stretches miles overhead. These are generally fair-weather clouds. But the secret to producing a fallstreak hole comes from what the clouds are made out of — not ice, as would be expected, but water.
The clouds are high enough that temperatures are well below freezing. But there’s nothing for the water droplets to freeze onto. So they remain supercooled, suspended in the atmosphere with no place to go.
Until a plane flies through them, that is.
It’s believed that commercial aircraft — which eject water vapor, aerosols and soot — can play a role in “seeding” the clouds. The newly introduced nuclei give the supercooled a surface to freeze to.
The result? The cloud “disappears” into a trail of newly minted ice crystals. Once in a while, a rainbow-like patch of color can appear in the diaphanous, wispy tail.
If we take a look at satellite imagery from this morning, the first thing we notice is scores of contrails over the Interstate 10 corridor:
But if we focus in a little bit closer, we notice a patch of fallstreak holes in the cloud cover, along the southern periphery of where the contrails disappear.
These were the ones that Reinert spotted, including a few in the immediate Orlando vicinity. There were even some before the sun rose. We can’t use visible satellite to discern those, but they did appear on water vapor imagery:
Additional fallstreak holes were captured in South Carolina. More sightings occurred in Canada, where Weather Network meteorologist Tyler Hamilton reviewed flight data to determine the planes potentially responsible.
Once in a great while, similar supercooling processes in the wintertime can actually result in an airplane producing its own snow showers:
Of course, no snow is in the forecast for Florida. But keep an eye out over the next couple of days. More fallstreak holes may be in the offing.
Check out this fallstreak hole that was sent in from Orlando, FL this morning! This happens when part of a cloud layer forms ice crystals that are large enough to fall as a 'fallstreak'. ☁️#flwx @NWSMelbourne— Christopher Pipkin (@ChrisPipkinWx) November 22, 2019
📸: Griffen Birdsong pic.twitter.com/96brpbAYwt
Many of you saw this unusual sight this morning. It's call a "Hole Punch Cloud' or "Fallstreak." It's a large gap in altocumulus clouds. Droplets in these clouds can be colder than freezing, but yet to freeze. Planes passing through produce ice crystals, making the hole. pic.twitter.com/V6NpaM5ko7— Rusty McCranie (@RMcCranieWFTV) November 22, 2019