Predicting Hail Storms - 101
Without being a highly trained professional working for the Australian Government Bureau of Meteorology (such as the lady I've paraphrased below), there is no fool proof way to predict when a storm will result in hail. But you can stay slightly ahead of the pack, if you understand the general patterns of a storm. Because isn't that all we're really after? A chance to get the clothes off the line and the car undercover?
Hail stones are a result of rapid updrafts during a thunderstorm. Sam Slattery from BOM explained the process to ABC Adelaide's morning program back in 2016. As I warned above I'm just going to paraphrase cause if ya'll wanted smart science you wouldn't have click on little ol' me.
For hail stones to form, we need a couple of things to align, moisture, atmospheric instability and intense, warm updrafts of air. The recipe is as follows.
Warm air rushes upwards, the moisture is lifted and pushed into the cooler parts of the atmosphere. Intense updrafts cause the moisture to become trapped in a "cyclic, tumbling wind pattern". As the lift created from the updraft becomes strong enough to keep the moisture aloft, small hail stones will form. Small stones will continue to be tossed upwards and grow until they are large enough for gravity to pull down, but the moisture below the storm and the speed of the updraft will also help to determine the size of the stones.
I still didn't really understand the above paragraph, so i read some more info to be able to break it down further. When warm air has a strong enough force to continuously push rain up into the moisture of the storm clouds, small, tiny stones form. If the updraft is strong enough to keep sending the little tiny stones up, they will grow on each trip, until finally gravity steps in and boom! Instant hail storm!
So now you know, if a thunderstorm rolls in and its pretty warm outside, look at the wind pockets and note their direction. If you're anything like me; you'll be grabbing the washing off the line, and bringing the pup in just in case either way!