Above her aunt’s farm near Scott Creek, South Australia, Chandra Hale (Member 49,371) watched at sunset as a line of lobe-shaped clouds rotated across the sky. They were remnants of what looks to have been an afternoon storm.

This formation, when it was in its full glory, would have been described as an arcus cloud feature. This is a low, arching ridge of cloud that juts out along the leading edge of large Cumulus congestus shower clouds or even more powerful Cumulonimbus storm clouds. Forming along the front base of the storm, an arcus sometimes looks a smooth ledge of cloud, sometimes a roughened, broken one. It generally appears just ahead of the storm’s heavy showers.

As the day came to an end, the storm likely dissipated and only the remains of its arcus reached Chandra and her aunt. ‘We watched the formation change colour every minute or so,’ she said, ‘rotating as it moved across the sky. This was time well spent.’