More than a cloud formation, what Jane Wiggins saw above the prosaic skyline of her central Iowa town looked like a foreboding, storm-incited sea at war with itself.
"It was frightening," Wiggins recalled Wednesday.
A professional photographer, she knew high drama when she saw it, and on that day a decade ago she took a picture that would become an international sensation.
When the World Meteorological Organization's International Cloud Atlas is released on Thursday, the cloud formation in her photograph will appear with the designation asperitas, Latin for "roughness." And it will be in a collection unlike any previous WMO catalog of those masses of minute liquid particles that we call clouds.
This will be the first updated atlas in 30 years, and Steve Cohn, the head of the WMO's 11-person cloud task force, said in part it is aimed at establishing order in the cloud universe.
With the proliferation of cameras and smartphones, cloud images have never been more plentiful. Ironically, that has helped cast a cloud over the identification system, with various online atlases threatening "global standardization," he said.
For the first time the WMO atlas will be digitized and include 600 images, triple the number in the previous printed version.
Among the entries will be asperitas (that's third declension, feminine, for all you classical scholars), and several others that will constitute WMO's first new cloud classifications in more than 60 years.
Said Wiggins: "Awesome!" Or should we say "optimus."
Atmospheric scientists apply these high-sounding Latin names to one of nature's most ethereal phenomena the way biologists label life forms on terra firma.
This cloud-naming business started with Luke Howard, a 19th-century figure called "the father of meteorology." He applied Latin names to the four basic shapes: cumulus, as in puffy; stratus, layered; cirrus, wispy; and nimbus, what we see when it rains or snows.
The WMO atlas organizes those cloud types into 10 "genera," and further subdivides the categories into "species;" "supplementary" features, including asperitas this time around, and "accessory" clouds.
So why bother doing this?
The categories are of scientific importance, said Cohn, formerly with the National Center for Atmospheric Research, in Colorado. They ensure uniform observation worldwide, and cloud-type information is a component of numerical weather-forecast models.
But other reasons are purely unscientific.
"Clouds are inspiring," Cohn said. "Consider children looking at the sky and asking questions. It's easy to say, `That's a pretty cloud,' but also great to be able to say, 'That's a growing cumulus cloud. Maybe it will become a cumulonimbus and there will be a big thunderstorm over there.'"
Back in 2006, Wiggins could not have known she was looking at something that would wind up in an atlas.
An acquaintance suggested she send the photo to the Cloud Appreciation Society, run by Gavin Pretor-Pinney, an Oxford-trained British philosopher and author of the best-selling The Cloudspotter's Guide, who took it from there.
The photo drew responses from all over the world by people who had seen similar formations. (It has been spotted in State College, and likely appeared over Philadelphia, as well.)
Pretor-Pinney appealed to the Royal Meteorological Society in 2009 to have it classified officially and ultimately to the WMO, the high court on cloud matters. After eight years, the court has decided in his favor.
Pretor-Pinney, who says his group boasts 43,000 members in 110 countries, was un-resentful about the delay.