Our own worst enemies: Researchers say cities most prone to hailstorms, and we’re causing them

Hail storms will increase in frequency and intensity and are more likely to wreak havoc across Australia’s most populous cities.

Oct 13, 2023, updated Oct 13, 2023
Researchers say big hailstorms are becoming more common in our big cities, which are contributing to the problem. (Photo: 7 News)

Researchers say big hailstorms are becoming more common in our big cities, which are contributing to the problem. (Photo: 7 News)

Researchers studying changing atmospheric patterns across the country found the number of days where the atmosphere has all the required ingredients for a hailstorm to form has increased in heavily populated areas.

In Australia’s southwest and southeast around Perth and Sydney, the increase was up to 40 per cent.

Scientists from the University of New South Wales and the Bureau of Meteorology used historical estimates of atmospheric conditions with the known ingredients required for a hailstorm to develop to study how the frequency of hail events has changed over time.

The team used the findings to make an indication of whether each day was hail-prone.

Lead researcher Tim Raupach from the UNSW Climate Change Research Centre said hailstorms required certain atmospheric “ingredients” to form.

These include a propensity for updrafts to form where warm air near the ground meets cooler air further up, enough moisture for liquid water and ice and strong wind shear.

“We found that the number of days considered hail-prone have decreased over much of the country, but increased over the southwest and southeast where there are large population centres,” Dr Raupach said.

“Even though not every hail-prone day produces hail, we can say that if there are more hail-prone days, there is an increased chance of hail.”

The assumption a warmer atmosphere under climate change meant hail had a greater chance of melting by the time it reached the ground was also not necessarily true, researchers said.

A warmer atmosphere would be expected to be more unstable, leading to the generation of bigger hailstones.

Because large hail is more likely to survive increased melting, when stones do form it may be larger and more severe.

“Where you have increased instability, then you might get more generation of hail and larger hailstones being generated in those regions that might survive more melting,” Dr Raupach said.

The findings are significant when researchers looked at increasing hail risk.

“Hailstorms can raze crops, the insurance industry, because of the damage hail can cause, and for city planning,” Dr Raupach said.

“We need to think about resilient agriculture that can deal with potential increases in the hail hazards.

“And likewise, how we can protect our densely populated areas from damage due to hailstorms.”

The study was published in the Nature journal Climate and Atmospheric Science on Thursday.

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