Australian Weather Calendar: April 2020

April photograph by Cathryn Vasseleu Photography

Lava-lamp skies

It was on a road trip from Darwin to Adelaide that Cathryn Vasseleu noticed an interesting cloud formation during a stopover at Lake Hart. 'We were taking photos of the salt lake, and when I turned around the sky looked just like a lava lamp!' she says. As an independent filmmaker, Cathryn spends a lot of time travelling around Australia, but says she'd never seen a scene like that before. 'It's such dramatic countryside—the bright white lake, red earth, and bright blue sky. I remember it was very dusty and the dust had given the clouds a pinkish lining, it was just fascinating.' Cathryn says she's been taking photos her whole life, and is drawn to weather events that are dynamic—in fact, one of her lightning photos from Nightcliff, Northern Territory, also appeared in the 2016 Australian Weather Calendar. When talking about her passion for photography, Cathryn's whole face lights up, 'I'm happiest when I've got a camera in my hand,' she says.

The science

The cloud shown in this photograph is known as stratocumulus lenticularis duplicatus, commonly known as a lenticular cloud. These clouds are near stationary and lens-shaped, usually forming downwind of a mountain range or elevated area. At times they can also form over ridged ground, as shown in this photo. As wind passes over ridged ground it becomes turbulent due to the disruption to its flow. This sometimes produces a wave pattern in the flow and, under certain conditions, moisture in the air will condense as it moves up towards the crest of the wave, forming cloud. As the moist air descends towards the trough of the wave, the cloud particles may evaporate again, which creates the distinctive lens shape.