Hailstone library to improve extreme weather forecasting

A hailstone, flecked with paint to assist in 3D scanning, being processed and added to UQ's hailstone library.

A hailstone, flecked with paint to assist in 3D scanning, being processed and added to UQ's hailstone library.

A University of Queensland library – full of hailstones instead of books – is helping researchers better understand and predict damaging storms. 

Dr Joshua Soderholm, an Honorary Senior Research Fellow from UQ’s School of the Environment, and lead researcher PhD candidate Yuzhu Lin from Penn State in the US, have found storm modelling outcomes change significantly when using real hailstones.

Key points:

  • Researchers are measuring and scanning samples for a global ‘hailstone library’
  • Storm simulations using 3-D modelling from real hailstones show it behaves differently to spherical hail shapes
  • Data from the hailstone library could lead to more accurate storm forecasts

“People tend to think of a hailstone as a perfect sphere, like a golf ball or cricket ball,” Dr Soderholm said.

“But hail can be all sorts of weird shapes, from oblong to a flat disc or have spikes coming out – no two pieces of hail are the same. 

“Conventional scientific modelling of hail assumes spherical hailstones, and we wanted to know if that changed when non-spherical, natural hail shapes are used.”
A person is crouched down behind a camera, shooting pictures of a white hailstone mounted on a stand.

Dr Soderholm photographs a rotating hailstone to map its shape in 3D.

Dr Soderholm photographs a rotating hailstone to map its shape in 3D.

Ms Lin said they found the differences were dramatic.

“Modelling of the more naturally shaped hail showed it took different pathways through the storm, experienced different growth and landed in different places,” Ms Lin said.

“It also affected the speed and impact the hail had on the ground.

A still image from a video of hail moving through a simulation of a storm.

The trajectory of naturally shaped hail inside the simulation of a thunderstorm. Image: Matthew Kumjian, Penn State.

The trajectory of naturally shaped hail inside the simulation of a thunderstorm. Image: Matthew Kumjian, Penn State.

“This way of modelling had never been done before, so it’s exciting science.”

Dr Soderholm said building a ‘hailstone library’ was critical to further fine-tuning hailstorm simulations.

“This is effectively a dataset to represent the many and varied shapes of hailstones, to make weather modelling more accurate,” he said.

“Our study used data from 217 hail samples, which were 3-D scanned and then sliced in half, to tell us more about how the hailstone formed.

“This data is now part of a global library, as we try and get a really clear picture of hailstone shape and structure.” 

Two gloved hands each holding half of a hailstone that's been sliced open

A cross section of a hailstone can tell researchers how it formed.

A cross section of a hailstone can tell researchers how it formed.

Dr Soderholm said the research has significant potential. 

“At the moment, the modelling is specifically for scientists studying storms, but the end game is to be able to predict in real-time how big hail will be, and where it will fall,” he said.

“More accurate forecasts would of course warn the public so they can stay safe during hailstorms and mitigate damage.

“But it could also significantly benefit industries such as insurance, agriculture and solar farming which are all sensitive to hail.”

A man in a green puffer jacket and beanie stands holding a hailstone outside a cold room door

Dr Joshua Soderholm with a hailstone for analysis.

Dr Joshua Soderholm with a hailstone for analysis.

The research paper was published in Journal of the Atmospheric Sciences.

Dr Soderholm is also a Research Scientist at the Bureau of Meteorology.

Some hail samples for the UQ data set were provided by Higgins Storm Chasing.

Interview, images and B-roll available via Dropbox.

Media contact

UQ Communications
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