The featured  event took place in Victoria, Australia.

These unusual formations called Fallstreak Holes are caused when the temperature of the water droplets in the cloud is below freezing but does not freeze. When the ice crystals do form, water droplets around the crystals evaporate leaving a large hole in the cloud.

Below is a Fallstreak Hole (also called a Hole Punch) in Austria.

Creative Commons License,  H. Raab