Behind the Forecast: Asperitas clouds - The sky’s rolling waves

Listen to Science Behind the Forecast with Meteorologist Tawana Andrew every Friday on 89.3 WFPL at 7:45 a.m.

Science Behind the Forecast: Asperitas clouds - The sky's rolling waves

LOUISVILLE, Ky. (WAVE) - Undulatus asperitas (or Asperitas) is the most recent cloud formation to be added to the World Meteorological Organization's International Cloud Atlas. The last cloud formation to be added before undulatus asperitas was the cirrus intortus in 1951.

Photo of Undulatus Asperitas cloud.
Photo of Undulatus Asperitas cloud. (Source: Lee Hartley)

The word asperitas comes from the Latin root aspero, which means to “make rough or uneven.” Undulatus means wavy. The term Undulatus asperitas translates to an agitated wave.

Asperitas looks like ocean waves in the sky. The base of the cloud can be anywhere from 4,000 to 10,000 feet up.

Asperitas is one of the new classifications in WMO's International Cloud Atlas and has really captured the public...

Posted by World Meteorological Organization on Sunday, June 11, 2017

How asperitas clouds form is still being researched. The current hypothesis is that their rippling appearance is connected to the aftermath of thunderstorms; however, they have been seen in calmer weather. There is a theory that asperitas clouds form when mammatus clouds (which look like udders hanging in the sky because of rising and falling air) drop into areas of the atmosphere where there is wind shear (a change in wind direction with height, which leads to the wave-like appearance and motion.

The Cloud Appreciation Society proposed the cloud’s addition to the International Cloud Atlas in 2008. Asperitas was added to the atlas in 2015, making it the first new cloud type in more than five decades.

Copyright 2020 WAVE 3 News. All rights reserved.