A ghostly white saucer hovers over the peaks of El Chaltén in southern Argentina. As wind thrashes the nearby clouds, the saucer remains fixed above the craggy summit, anchored in the sky like a mothership surveying the hills below.
This eerie weather phenomenon is relatively common in mountainous regions like El Chaltén, or the Rocky Mountains in the U.S., where high-speed winds ricochet over a tall peak, creating a distinct lens- or saucer-shaped cloud formation high in the sky. Still, photographer Francisco Javier Negroni Rodriguez — whose photo above is a finalist in the Royal Meteorological Society's (RMS) 2020 Weather Photographer of the Year contest — had to wait the better part of a day to capture the cloud in its mysterious glory.
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"An hour before taking this photograph I was walking along the trails that surround the beautiful rock formation … [but] the day was very cloudy. Apparently, luck was not with me on this adventure," Negroni Rodriguez told the RMS. "Only for a moment, the clouds allowed me to see El Chaltén — and to my surprise, there was a spectacular and brilliant lenticular cloud with a beautiful and perfect figure that I had never seen."
This type of cloud forms when strong wind blows into the side of a mountain, skyscraper or other tall obstruction, according to the National Weather Service. The mountain deflects the wind, forcing it into a wave that crests over the mountaintop, dips down on the other side, then rises up again. In the upward-moving parts of the wave, the air cools until it condenses into clouds. When the air descends again on the downward-moving side of the wave, the cloud evaporates. The result is a spooky, stationary cloud perched atop the crest of the wave, sculpted into a saucer shape by the wind constantly rising and falling within it.
Negroni Rodriguez's photo joins 25 other finalists in the RMS contest, which is co-sponsored by AccuWeather. While the alien cloud was not one of the three grand-prize winners announced on Oct. 17, it nevertheless rose to the top of more than 7,700 entries, according to the RMS. To see some of the other stunning finalists — including the big winners — click through this gallery.
Originally published on Live Science.