Huge mass triggers weather radar – but it's not what it seems

·News Reporter
·2-min read

A rain radar has seemingly captured an unusual weather pattern, but it turns out it’s something different entirely.

The National Weather Service in Phoenix, in the US state of Arizona, picked up massive returns on its radar on Monday between 6pm and 7pm (local time).

It posed the question to people on Twitter whether it was “rain or something else” and included a GIF of the movement.

A still of a green mass over a map of Phoenix on a radar picked up by the National Weather Service.
The National Weather Service picked up this unusual movement on their radar. Source: NWS Phoenix/Twitter

Some people guessed it was hordes of insects. One man suggested it could be dust or smoke.

However, those guesses were wrong.

“Plenty of great replies! Many have guessed it! It's definitely not chupacabras, tacos, aliens, or gender reveal parties though,” the weather service tweeted.

It turns out, the movement on the radar was caused by “thousands of Mexican free-tail bats” migrating to Phoenix for the summer.

One of some 1.5 million bats emerges from below the Congress Street Bridge near downtown Austin, Texas.
A Mexican free-tail bat emerges from under a bridge in Texas. Source: AAP

According to Arizona Game & Fish, the bats normally seek out their home in the Maricopa County Flood Control Tunnel and have done so for about 20 to 30 years.

One person asked how the weather service could determine whether the movement was bats or birds.

The weather service explained it was “the pattern of movement and the timing that are the distinguishing details”.

“When similar patterns are seen early in the morning and over/near bodies of water, that's more indicative of birds,” it tweeted.

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