Lenticular clouds: Mount Rainier, Washington State
Lenticular clouds: Mount Rainier, Washington State, USA
It's easy to see how these rare clouds (pictured) could be mistaken for UFOs. Occasionally, when strong gusts are forced upward by mountains, wind-borne water vapour condenses into surreal shapes resembling fluffy flying saucers. Conditions have to be just right for this to happen -- so don't count on seeing a lenticular cloud -- but your best bet may well be from a vantage point near Washington State's Mount Rainier. The 4,392-metre stratovolcano is the most prominent peak in the continental United States, meaning there's little to stop strong Pacific winds from buffeting it. It's as close as Earth gets to producing a "recipe" for lenticular clouds, not to mention inspiration for science-fiction.