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'Rainbow cloud' spotted over Tasmania actually snap of 'rare' cloud iridescence

By Megan Macdonald, Thursday July 18, 2019 - 13:15 EST
ABC licensed image
Heather Murphy's photo of cloud iridescence in southern Tasmania. - ABC licensed

A rainbow-soaked cloud that appeared over Tasmanian skies this week has wowed some social media users and confused others, with many left wondering what it is and whether it is even real.

The photo, posted by Heather Murphy on the Facebook group earlier this week, was taken in Collins Street in Hobart's CBD and showed the cloud awash in rainbow colours.

"Never seen anything like that," Andrea Hewett commented.

"I didn't know rainbow bridges actually existed until today," Anne Allan said, adding the sight was "amazing".

"That is one in a million," Helen Rogers said.

The Bureau of Meteorology (BOM) was equally impressed with Ms Murphy's shot, reposting it on their Facebook page with a scientific explanation: .

The BOM explained in their post that the spectacular sight was often a result of sunlight passing through thin, high clouds that are made up of tiny water droplets.

Forecaster Lizzie Donovan said the photo was a beautiful example of the natural phenomenon.

"Cloud iridescence happens when you get sunlight diffracting off water droplets within a cloud," she said.

"The sun will encounter the water droplets and scatter off the edge. It's like a little obstacle."

Is it a rainbow?

Ms Donovan said while cloud iridescence may look like a rainbow, the science behind what was happening was different.

"Rainbows are caused by refraction and then shifted off into another direction. The colours [in the cloud] are spread randomly, unlike a rainbow," Ms Donovan said.

Ms Donovan said because Tasmania encounters many cold fronts, the likelihood of spotting the colourful clouds was higher than it was in other states.

"We are lucky in Tasmania because we do get a lot of high cloud which is common when there is a cold front approaching … which we get a lot of here!" she said.

Alongside spectacular cloud iridescence sightings, .

Is cloud iridescence rare?

Ms Donovan said that it was difficult to know how often cloud iridescence occurred, meaning the photo on social media was a lucky sight.

"The fact I haven't even seen one makes me think they are rare," she said.

She said the photo was "very well captured", but recommended the other budding photographers be careful if they tried to get a similar shot.

"Don't snap the sun … put that hand up to block it and you should still be able to capture that iridescence," she said.


© ABC 2019

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