A newly recognized and mysterious cloud formation
Asperitas clouds, formerly known as Undulatus asperatus, are among the most striking and unusual cloud formations ever observed in the sky.
They were first proposed as a distinct cloud type in 2009 by Gavin Pretor-Pinney, founder of the Cloud Appreciation Society, and officially added to the International Cloud Atlas in March 2017. This marked the first addition of a new cloud classification since 1951.
The name “Asperitas” translates roughly to “roughness,” perfectly describing their dramatic, wave-like appearance.
A sky that looks like a turbulent ocean
What makes Asperitas clouds so unique is their extraordinary texture. The underside of the cloud layer appears chaotic and undulating, resembling rough ocean waves seen from below.
The sky often takes on a dark, almost apocalyptic look, with rolling patterns that seem to move and shift, creating a surreal visual effect rarely seen in typical cloud formations.
Why they look dangerous but usually aren’t
Despite their ominous and storm-like appearance, Asperitas clouds rarely lead to severe weather.
In most cases, these clouds form after convective activity, such as thunderstorms, when the atmosphere is still unstable. However, instead of developing into new storms, the clouds gradually lose energy and dissipate.
This contrast between their threatening look and relatively harmless outcome is one of the reasons they attract so much attention.
Where and when they are most commonly seen
Asperitas clouds have been most frequently observed in the Great Plains region of the United States.
They typically appear during the morning or midday hours, especially after earlier thunderstorm activity has passed through the area.
Although they can form in other parts of the world, sightings remain relatively rare, making each appearance a remarkable atmospheric event.
A modern addition to cloud science
The recognition of Asperitas clouds highlights how atmospheric science continues to evolve, even in areas that might seem well understood.
Their official classification in the International Cloud Atlas not only validated years of observations but also demonstrated the role of citizen science and public interest in advancing meteorology.
