At a Glance
- A curious cloud hole over Austin on Thursday is a fallstreak hole.
- These holes appear in cirrocumulus or altocumulus clouds.
- They form when supercooled droplets freeze on ice crystals and fall.
- Why it matters: It explains a common but puzzling atmospheric phenomenon viewers saw.
A strange hole in the sky over Austin last Thursday caught the attention of local viewers and the News Of Austin First Warning Weather team. The feature, which looked like a punch in the clouds, is actually a fallstreak hole-a natural atmospheric event that can create large gaps in high-altitude cloud layers.
What Is a Fallstreak Hole?
A fallstreak hole is a large circular or elliptical gap that can appear in National Weather Service-defined cirrocumulus or altocumulus clouds. Meteorologists often call them “hole punch clouds” because the gaps look like a punch-through.
- Cirrocumulus clouds
- Altocumulus clouds
- Large gaps, often circular or elliptical
How They Form
Fallstreak holes form in mid- to high-level clouds that contain tiny water droplets colder than freezing but not yet frozen-known as supercooled droplets. These droplets seek a surface to freeze onto, usually ice crystals. Planes passing through the layer can supply the necessary ice crystals.
Once a droplet freezes on an ice crystal, gravity pulls the ice crystal-laden droplet downward, leaving a hole behind. As surrounding droplets freeze and fall, the hole can grow larger.
Key Takeaways
- Fallstreak holes are natural gaps in high clouds caused by freezing supercooled droplets.
- The phenomenon is common but often misunderstood by the public.
- Observing a hole in the clouds is a sign of active atmospheric processes at high altitudes.
The News Of Austin First Warning Weather team encourages viewers to share photos of unusual cloud formations through News Of Austin ReportIt, helping scientists study these intriguing sky features.
