Rain accidentally appears on weather radar as 'jaw-dropping' occurrence blackens sky

Australia’s national weather service appears to have malfunctioned after a natural event tricked a radar into concluding a downpour was imminent.

Ecologist Dr Keith Bishop had noticed that on most evenings, indications of rain would suddenly appear on the Bureau of Meteorology (BoM) radar map when the sky was completely clear. The massive cloud would regularly form above the NSW Mid North Coast village of Smiths Lake, travel southwest for 20km, and then disappear once it reached the Myall Lakes National Park.

The strange, natural phenomenon appearing above Smiths Lake would have no doubt baffled many of the tourists visiting the area over Christmas and New Year, but as a local, Bishop believed he new what was triggering it.

He’s observed a large colony of grey-headed flying foxes fly through the area since the 1990s, and he suspected when they swelled in numbers over the summer period, their nightly migration from roosting trees to feeding ground was likely enough to trigger a blip on the weather radar.

“Between Christmas and New Year you could physically see they were precisely leaving between 8:05pm and 8:10pm. The sky goes dark on days when there’s no rain at all,” he told Yahoo News Australia. “But on the radar this blip would emerge… and then disappear when they go into the trees (in the national park.”

BoM reveals strange phenomenons that radars detect

Yahoo first became aware of the flying fox colony's apparent effect on the radar, when video of the occurrence was uploaded to X (formerly Twitter) by Keith's son. It shows vision of a cloud taken in the last week of 2023 beside vision of bats flying in the sky.

The team at BoM told Yahoo it couldn’t confirm the flying foxes were directly responsible for the blip, but non-weather related events have been known to trigger responses from radars.

“Radars do sometimes detect echoes from aircraft, areas of smoke/ash from large fires, swarms of insects, interference sources, flocks of birds or even the ground or sea surface, when unusual atmospheric conditions bend the radar beam back down to the surface,” it said. “As a result, there may be patterns on the radar images that do not represent falling rain.”

Idyllic NSW town that loves its flying foxes

Some Australians living in manicured suburbs around Queensland and NSW vehemently hate flying foxes because they can foul their concrete driveways, carports and swimming pools, and the mayor of the Sutherland Shire even told council they should be shot. But the residents of Smiths Lake generally admire the creatures.

Flying foxes are the nation’s only long-range pollinators, and they are essential for the health of eucalypt forests as they can spread the genetics of trees that live tens of kilometres away.

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While grey-headed flying foxes can be seen in great numbers, they are listed endangered as their populations are decreasing, and their future is threatened by habitat loss through agriculture and housing developments as well as climate change.

Radars are used to track flying foxes elsewhere in the country. The CSIRO and Western Sydney University project uses the technology to monitor colonies from Hervey Bay to the Adelaide Botanic Gardens that it considers nationally significant.

With the Smiths Lake’s ten flying fox camps are believed to be home to thousands of flying foxes, Bishop believes the region’s colonies would be a good candidate to be added to the Flying Fox Radar-Monitoring program. “Watching them in the sky is incredible, it’s like being in a David Attenborough special — it’s just jaw dropping. They just go on for 20 or 30 minutes, a black line heading out in the southwest direction,” he said.

“It’s also heartening that residents around here are very protective of them.”

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