PHOTOS: Wavy ‘asperitus’ clouds over Central Texas

Georgetown. (Report It: Kristen Posey)
Georgetown. (Report It: Kristen Posey)

After two full weekends of wall-to-wall sunshine this month, this weekend has been a tad more cloudy and stormy than we probably would have liked. With that increasing low cloudiness across the KXAN viewing area brought “wavy” cloud formations on Sunday. Which had many folks reaching out to our meteorologists and asking what was causing the clouds to take on such a “wavy” shape?

The cloud formation is called “asperitus” or “undulatus asperatus,” which means “agitated waves.” This “undulation” or wave-like motion in the atmosphere is created by ocean-like waves of air moving horizontally, meeting up with a deck of developing low clouds. Voilà…you’ve got waves in the sky!

The cloud formations only recently received their own designation in the International Cloud Atlas. Here’s what the World Meteorological Organization wrote about them:


Most public interest has focused on a proposal by the Cloud Appreciation Society, based in the UK, to recognize the so-called “asperitas cloud (Latin for roughness). The international Task Team defined this as “well-defined, wavelike structures in the underside of the cloud, more chaotic and with less horizontal organization than undulatus. It is characterised by localized waves in the cloud base, either smooth or dappled with smaller features, sometimes descending into sharp points, as if viewing a roughened sea surface from below. Varying levels of illumination and thickness of cloud can lead to dramatic visual effects.”

Undulatus already exists as a cloud variety, the third level of classification, which is generally associated with stratiform clouds. The Task Team has proposed that asperitas (note spelling: after the Latin noun meaning roughness) be included as a new supplementary feature, and has selected an image for inclusion in the new Atlas, based on a competition by the Cloud Appreciation Society. provides commenting to allow for constructive discussion on the stories we cover. In order to comment here, you acknowledge you have read and agreed to our Terms of Service. Users who violate these terms, including use of vulgar language or racial slurs, will be banned. If you see an inappropriate comment, please flag it for our moderators to review.

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