Alabama skies covered by stunning wave clouds

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The skies above Alabama on Thursday were transformed into a rare display of a cloud known as undulatus, as well as an even more rare and highly prized cloud formation among atmospheric aficionados: undulatus asperatus. Undulatus asperatus, or turbulent wave clouds, have been the subject of a quixotic advocacy campaign by the UK-based Cloud Appreciation Society, which is a lobbying group for cloud fanatics worldwide. Social media posts show that the sky was full of undulatus, or "wavy," clouds above Alabama as a mixture of sleet, snow and rain moved into the region on Thursday morning. Both types of clouds reveal turbulent wave motion of varying amplitudes. The World Meteorological Organization (WMO) defines undulatus asperatus clouds as:

"A formation made up of 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."

The WMO notes that undulatus already exists as a cloud variety, and a WMO team has proposed that "asperitas," derived from the Latin word for roughness, be added as a supplementary feature. That decision is still pending action on the part of a WMO executive council, which means that cloud policy red tape is slowing things down.