After a 'UFO' was spotted over Los Angeles earlier in the week, residents of Cape Town in South Africa would have been forgiven for thinking they were facing an alien invasion after strange-looking clouds formed over the city.
Bizarre shapes formed in the sky over the one of the nation's capitals on Sunday, dwarfing Table Mountain and looming ominously.
Fortunately, the odd structures were just lenticular clouds, unusual and rare cloud formations that could prodvide an explanation for some historical UFO sightings.
The clouds form when air travelling across the ground meets an obstruction, like mountains or buildings. As air flows over these obstructions, large, stationary waves may form on the downwind side.
If the air at the top of these waves drops to a sufficiently low temperature, the moisture in the air condenses to form the odd, still clouds.
Cape Town is surrounded by a number of mountainous areas, so it's not surprising that so many lenticular clouds appeared in the sky.
Lenticular clouds are fairly uncommon in most places, and a lot of people have no idea they even exist - so many UFO skeptics consider these clouds to be potential explanations for unexplained alien sightings.
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