Australian Weather Calendar: July 2020

July photograph by James Dun

A feather in his cap

While he’d dreamed of a career as a meteorologist when he was younger, James Dun never thought his love of weather would land him in the Australian Weather Calendar. 'I was born in Katherine in the NT and watching the big storms roll through as a kid really started my fascination with the weather,' James says. 'Weather photography is my favourite thing outside work, but it’s really just a hobby so I’m pretty excited to make the calendar.' It was on a trip to Darwin to witness and photograph the area’s famous wet season storms that James found himself looking up at this cumulonimbus cloud with another amazing feature—a cap cloud. 'I’d photographed cap clouds before, but the layers in this one were just spectacular,' James recalls. 'The frequency and intensity of the storms in Darwin, particularly the lightning, it’s just something else.' And when it comes to photographing them, we take our hat off to him!

The science

The fine, smooth layer of cloud visible above this cumulonimbus (thunderstorm) cloud is a pileus cloud, also known as a cap cloud. Pileus clouds are formed by rising air pushed upwards ahead of the strong updrafts in tall, convective type clouds like this one. Forming high in the atmosphere, they are made of ice crystals. The ice crystals give the cap cloud a very smooth appearance. Occasionally multiple layers of pileus clouds can be visible, before they become part of the bigger cloud.