It looked like the opening scenes from a summer blockbuster movie as a fleet of "UFOs" hovered over Cape Town, South Africa on Sunday. But there were no alien invaders -- just a stunning lenticular cloud formation.
The unusual and eye-catching display had many wondering what they were witnessing:
Lenticular clouds, named because of the lens-like shapes they create, are usually formed by air flowing over mountains, reports EarthSky:
"When this happens, a series of large-scale standing waves may form on the mountain’s downwind side. If the temperature at the crest of the wave drops to the dew point, moisture in the air may condense to form lenticular clouds. As the moist air moves back down into the trough of the wave, the cloud may evaporate back into vapor. So lenticular can appear and disappear relatively quickly."
The clouds can also form in places where there are no mountains if the wind conditions are right, according to EarthSky.
National Geographic says these clouds were stratocumulus standing lenticularis clouds due to their height and shape.
Here's another look at them:
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