What's that strange sight high up there in the sky? It doesn't look like a bird. Could it be an airplane? Maybe it's a UFO! Nope! None of the above — it's just a cloud.

It might not just be any type of cloud, though. If it looks a bit like an unidentified flying object, chances are it's a special type of cloud called a lenticular cloud.

Lenticular clouds get their name from the fact that they're shaped like a lens or a saucer. This is why they're also sometimes called “flying saucer clouds" and sometimes mistaken for UFOs. Some other nicknames for lenticular clouds include “cloudships," “clouds of heaven" and “lennies." They also have a fancy scientific name: Altocumulus lenticularis.

Although lenticular clouds may look like they're from outer space, they're actually just the result of normal earthly scientific processes. Lenticular clouds are stationary clouds that form at high altitudes in the sky. They're usually aligned at a right angle (perpendicular) to the direction of the wind.

For example, when stable humid air blows over the top of a mountain range, it often forms a group of big waves on the downwind side of the mountain range. If the temperature is low enough on the downwind side, the moisture in the air will condense to form uniquely-shaped clouds we know as lenticular clouds.

If the conditions are right, these groups of wave after wave of lenticular clouds can form what scientists call a “wave cloud." Lenticular clouds are also unique in that sometimes you may see bright colors — what scientists call irisation — along the edges of the clouds. This can give them a definite outer space feeling!

Airplane pilots will usually try to avoid flying near lenticular clouds. The waves of air that form the clouds can cause turbulence, which means riding in an airplane near lenticular clouds can be a bouncy, scary experience.

People that fly gliders, however, love lenticular clouds. The same air currents that can make flying in an airplane scary allow gliders to sail to great heights and long distances.

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Brace yourself! Tomorrow’s Wonder of the Day may make you smile.