Australia Weather News

Hail in Australia causes more damage in terms of insurance losses than any other aspect of severe weather in thunderstorms.

Thunderstorms often contain strong updrafts that can suspend a large amount of rain, sometimes these water droplets can be carried high up into the cloud where they can freeze into small pieces of ice. Additionally some of the water droplets do not freeze despite falling below 0C and become what's known as "supercooled water droplets."

These supercooled water droplets when coming into contact with other pieces of ice and instantly freeze with this process occurring for many tens of minutes. Often the ice (or hail), falls to ground quite quickly with the updraft not being strong enough to support the weight of the hail. However in very strong thunderstorms hailstones can sit in the cloud for much longer – sometimes growing to larger than cricket ball size!

What's impressive is that it's just the speed of the air rising up in the atmosphere that’s suspending this high up in the cloud. Think about the speed the air would need to travel just to move a cricket ball along the ground – let alone lift it up off the ground and carry it into the atmosphere and that gives you an idea about how strong updrafts in storms can be. Fortunately such storms are very localised. Many storms also contain hail that melts before reaching the ground as the small hail has to travel for a couple of kilometres in warmer temperatures before reaching the ground which can cause it to melt.

The largest hail in Australia generally occurs along the east coast between Sydney and Brisbane. This is because the moisture off the warm Coral and Tasman Seas helps bring very high instability and interacts with the upper troughs approaching from the west. This very high instability helps with updraft speed and intensity – giving the potential for very large hail to occur but large hail can occur in most areas of the country – albeit fairly unlikely and very rare in the tropics.