From Iowa to England, the World’s Newest Cloud Is Challenging the Status Quo

Wave-like cloud formations, now recognized as asperitas, were first recorded in 2008 by the Cloud Appreciation Society based in England. This past spring, the same clouds were spotted across the Midwestern United States. Described as “rare” by Fox Weather, asperitas clouds are perhaps better described as simply new — the only cloud, in fact, added to the International Cloud Atlas since 1973. Cover graphic by Emily Fischer for Midstory. Original image courtesy of Josh Carson via Flickr.

The Cloud Appreciation Society founder Gavin Pretor-Pinney first received a photo of a peculiar wave-like cloud formation from a woman in Cedar Rapids, Iowa, in 2008.

“Very much like the surface of the ocean when you’re underneath, looking up. But not on a kind of calm day with regular waves — more on a chaotic, choppy day,” Pretor-Pinney said. “You could say it is a form of undulatus, but it seemed so chaotic and turbulent.” 

The society’s website hosts a photo gallery where members can submit photos and administrators will identify their clouds. After reviewing very similar images from Wisconsin, Australia and Greenland over subsequent months, Pretor-Pinney said he believed the cloud could not be accurately categorized with existing cloud names. 

In his new role as detective, Pretor-Pinney’s first stop was the Royal Meteorological Society in England with proof of his new cloud in tow. 

“It was a little bit like a sort of X Factor thing. There were four of them sitting behind the table — like a panel — and I was showing them these photographs and saying, ‘I think this deserves to have a classification of its own,’” Pretor-Pinney said. 

In preparing for the cloud’s assessment, Pretor-Pinney called his cousin — a high school Latin teacher — to create a scientific name with lyrical depth. Pretor-Pinney said his cousin ultimately suggested using a quote from the poet Virgil, which included the verb “asperō,” or “to roughen the sea,” then converting it to a noun produced “asperitas.” 

“‘The sea was roughened by the icy Northern gales,’ I think was the phrase,” Pretor-Pinney said. “If you want Latin words, always go for Virgil because he wrote really good Latin.” 

Asperitas clouds over Newtonia, Missouri, U.S. Image courtesy of Elaine Patrick, Cloud Appreciation Society Member 31,940. 

The Royal Meteorological Society told Pretor-Pinney he had to take his appeal to the World Meteorological Organization (WMO) based in Geneva because they publish the official list of clouds in the International Cloud Atlas. The most recent edition had been published in 1973, and the first in 1896. Pretor-Pinney said although the WMO was reluctant to add a classification and release a new edition, media outlets caught wind of his efforts and pressured the WMO to validate the crowd-sourced discovery. 

“Who decides a cloud is a cloud?” Giles Harrison, a researcher and professor of atmospheric physics at the University of Reading, said. 

As citizens continued to send in photos of asperitas clouds, Pretor-Pinney sought scientific legitimacy from Harrison, who partnered with Pretor-Pinney to distinguish the cloud in the atmosphere. 

“We’ve sort of narrowed down some of the ideas. I don’t think we’ve got an exact description of the exact process, but we think it’s to do with turbulence, and that it modifies an existing cloud,” Harrison said. “The cloud is already formed, and then waves passing through the cloud give it this rather rough, sort of ocean wave-look to it. And I think it is pretty distinctive.”

In 2017, the same year Harrison gathered his findings, the WMO published a new edition of the International Cloud Atlas, including asperitas as its own entry. Harrison said he had never heard or been part of cloud advocacy like Pretor-Pinney’s story. He said that typically when people approach him about phenomena they’ve observed in the sky, it’s about lightning. 

“Science works by people seeing things and then trying to work out what they are. And different people will have different explanations. And only when you look back maybe 30 or 50 years from now will you know who was right,” Harrison said. 

John Mecikalski, scientist and professor of atmospheric science at the University of Alabama, said only about 15-20 “cloud experts” review the International Cloud Atlas at WMO on a yearly basis, and that the WMO keeps its cloud dictionary succinct to maintain a standardized measuring system and avoid confusion.

Before the WMO, a pharmacist from London suggested using Latin naming for clouds in 1802, according to Pretor-Pinney. Similar to how “stratus” and “cumulus” make up the term “stratocumulus,” practically any two Latin words could be combined to name a cloud. Pretor-Pinney said when the WMO took over the International Cloud Atlas, they enumerated which specific cloud names they would recognize. 

Asperitas clouds. Image courtesy of the World Meteorological Organization. 

As for asperitas’ Midwestern presence, Mecikalski said the region’s atmosphere lends itself to the kind of turbulence which produces the cloud formation. Moisture and humidity moving above cool air near the ground creates a developing, dynamic cloud, Mecikalski said. Cold air could be coming from Canada or a recent rainstorm, while warmer air could be coming from as far south as the Gulf of Mexico, he said. 

“Oftentimes they see these things right after a storm has come through, like a thunderstorm, or they’ll see these things in the springtime as warm, humid air is trying to move further north,” Mecikalski said. 

Asperitas clouds may also be appearing in the Midwest specifically because of frequent convective storms the region experiences in the summer, according to Mecikalski. Mecikalski also said a big reason he became interested in the weather and clouds was because they were always changing in his home state of Wisconsin. 

“There’s a large amount of meteorologists that have come from places like Wisconsin, Minnesota, all the way over to New York and Pennsylvania and Ohio,” Mecikalski said. “I’m gonna guarantee there’s a lot of hurricane meteorologists out there who came from Florida and the Gulf Coast.” 

If you see asperitas clouds in the sky, Mecikalski said it could mean a few different things: if it’s springtime, a warm front and storm could be on its way within the next day; if it’s during the summer, a large storm may have just passed through and others could be following within the next few hours. 

Back in England, Pretor-Pinney’s society of around 60,000 members thrives on their fascination with the giant masses of water we call clouds — each equivalent to 100 elephants — floating in the sky. 

“I always was intrigued by the fact that people love them and hate them here in the UK. They hate them because they rain unexpectedly on things. And they ruin your party or your barbecue or your wedding, so they’re out of our control. Humans don’t like things that are out of their control. But they’re also these vehicles of imagination, and they are the embodiment of escape, transformation. They are light-hearted,” Pretor-Pinney said.  

Graphic by Emily Fischer for Midstory. Original image courtesy of Neil Mansfield via Landscapes Uncovered.


  1. LUKE HOWARD of Tottenham, Quaker, was the man who did all the research and devised the original Latin system for cloud naming, inspired by Linnaeus’s binomial system for naming plants. Every current name for a major cloud type comes from Luke Howard’s original names for clouds.
    He does not deserve to be anonymous.


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