As if Londoners don't have enough weird visuals to process right now, what with endless photos of Donald Trump hanging out with the Queen, they were also treated to some apocalyptic-looking cloud formations above the capital yesterday.

If you stood still and looked up (which FYI is frowned upon and will get you tutted at like you're some kind of tourist), you would have seen these cloud formations hovering above the Houses of Parliament. Londoners brave enough to risk said tuts from fellow pedestrians stopped to snap some photos of the creepy, vortex-like formations.

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People asked questions ranging from a measured "huh this is interesting, any cloud experts around to explain what this is?" to "what the hell is this floating over south London?!" Some even likened them to black holes, and pointed out the coincidental timing of their appearance and a certain state visit.

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So what are they?

They look to be asperitas clouds, the Met Office told ITV News, a rare cloud formation that was only officially recognized in 2017.

"Asperitas is a distinctive, but relatively rare cloud formation that takes the appearance of rippling waves," according to the Met Office. "These wave-like structures form on the underside of the cloud to make it look like a rough sea surface when viewed from below."

The rippling, undulating effect can best be seen in this time-lapse video.

Nobody is quite sure how these clouds form, though their appearance has been associated with the aftermath of thunderstorms.

"One theory does suggest that they are formed when mammatus clouds descend into areas of the sky where wind direction changes with height causing the wave-like movement," the Met Office said.

Mammatus clouds are formed by turbulence within cumulonimbus clouds, especially visible on the underside. "This reverses the usual cloud-forming process of upward growth, making for an uneven cloud base."

Asperitus clouds are a rare formation more commonly seen over the plains of the United States, so the timing was impeccable that they appeared to visit London's tourist hotspots when the US President did as well.

Whilst you're here and looking at clouds, why not check out these bizarre hole punch clouds.

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