Q: There's supposed to be a type of cloud that is often confused with being a UFO. What kind of cloud is it?

A: It's most likely the lenticular cloud, says Brent McRoberts of Texas A&M University. Lenticular clouds are so-called because they often look like a camera lens. They can produce some of the oddest shapes of all clouds, many times looking like huge pancakes stacked on top of each other, he reports. "One reason they may be mistaken for UFOs is their odd shape," McRoberts explains. "Also, lenticular clouds don't move like other clouds ? they tend to linger in one spot for a long time. They are often seen in the western U.S. but have been photographed all over the world, including Spain, Australia and France."

Q: What causes their strange shape?

A: "Lenticular clouds are often formed by waves of air moving over high mountains," McRoberts adds. "At the highest points in the cloud, moisture condenses in an outward motion. By doing so, it tends to form a wave-like appearance and the edges are round, giving them the appearance of a flying saucer. Some scientists believe lenticular clouds tell us a change in the weather is coming, often meaning a snowstorm. If you can find photos of lenticular clouds in weather books, you'll agree that they are some of the strangest looking clouds produced by nature."

Weather Whys is a service of the Department of Atmospheric Sciences at Texas A&M University.
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