These are some of my favorite clouds to see, they’re called hole-punch or fallstreak clouds. And believe it or not, they didn’t exist before the invention of propeller airplanes. These clouds are picky, they need just the right combination of aircraft, cloud type, and temperature to form.
Let’s start with the history:
The first report of this unusual cloud appeared in Weather magazine in 1948, in an article titled “Man-Made Cirrus?” The author suspected that an aircraft had caused both the circular hole and the wispy cirrus cloud in its center, though at the time, no scientists could explain how this happened.
Two decades later, in 1968, Weatherwise magazine, which I actually subscribe to, published a photograph in a piece called “Hole-in-Cloud: A Meteorological Whodunit?” The image spread as widely as anything could in the pre-Internet 1960s and renewed interest in the mystery.
But it wasn’t until 2009 that scientists finally solved it. Using satellites, radar, and onboard aircraft instruments, researchers confirmed exactly how these clouds form, revealing that airplanes (C-130s) with propellers flying through supercooled clouds can trigger ice crystals to form, setting off a chain reaction that punches a hole right through the sky.
Let me explain:
For one of these “holes in the sky” to form, you first need the right kind of cloud, a mid- to high-level altocumulus cloud. These clouds are made up of tiny water droplets that are actually colder than freezing. Meteorologists call them supercooled droplets. They stay in that state until something triggers them to freeze, usually the introduction of ice crystals.
That’s where airplanes come in. When a propeller-driven plane passes through one of these clouds, the rapid air expansion near the propeller tips causes a sudden drop in temperature. That cooling creates ice crystals, which in turn trigger nearby supercooled droplets to freeze. Jet aircraft can also cause the effect, but propeller planes produce it more efficiently because of that extra localized cooling.
Once those ice crystals form, they start to grow and fall through the cloud layer, leaving behind a circular gap, the “hole.” As the freezing spreads outward, the hole expands. The wispy cirrus-like streak in the center marks the flight path of the plane that started it all. This picture by Mary Davis in Richmond, Texas, shows not just the hole-punch cloud but a continuous clearing and path of the plane.
If you ever see something in the sky you can’t explain, please share it with me at www.click2pins.com