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Meteorologist here. It's just an error in the decoding software that sometimes makes it to the web. Media calls us about it sometimes.
TL;DR: Radars don't actually take just one 2 dimensional scan of the sky, they actually do a whole 3D of the sky around them by doing multiple rotations at different elevations. For you normies who wouldn't have much interest in 3D RADAR data, it gets converted into 2D. Sometimes the computers choke out along the way because most radars around the place are ancient, and they shit out pictures like you see there.
I wish it was aliens but unfortunately it's just your countries RADAR computers being 1990 tier.
Pic related, me at the pub, since I just got called a glowie last time.