Move over, Twisters. These storm chasers are after hail

7NEWS

22-07-2025

A team of about 70 researchers, armed with high-tech sensors and specially outfitted vehicles, set out across the US this spring and summer to chase dozens of thunderstorms, hoping to unravel the remaining mysteries of how hail forms, whether hail storms are getting bigger in a warming climate and how to prevent damage.
Hail is a leading cause of storm damage in the US and was responsible for tens of billions in property losses last year, according to Gallagher Re, a global reinsurance firm that tracks such data.
Some previous modelling research suggests that the frequency of large hailstones striking the earth will increase with climate change.
The federally funded project, known as ICECHIP, is the first comprehensive field study of hail in four decades.
It is meant to fill in critical gaps in hail forecasting capabilities: connecting a storm's complex, internal dynamics to the amount and the size of hail it will produce. That data could help modellers develop better predictors of storm damage, as well as aid in developing building materials, like roofing, that can stand up to hailstones.
'We know that hail might happen today, but we don't know when, we don't know where, and we don't really know which of those storms is going to make 1-inch hail or 4-inch hail,' Joshua Wurman, a top academic storm chaser at the University of Alabama in Huntsville, who is deploying the mobile radars for ICECHIP, said.
'And there's a huge difference to people on the ground, to crops, to cars, to roofs.'
The chase
From mid-May through the end of June, ICECHIP storm chasers travelled across the Front Range of the Rockies and the central Plains, sometimes riding in vehicles armoured against falling ice.
They launched drones, released weather balloons and set up mobile doppler radars — all techniques honed by tornado chasers.
As one group positioned mobile doppler radars to intercept the storm at close range, other researchers were responsible for releasing weather balloons nearby or setting out sensors to measure the size and velocity of a hail strike.
During some storms, researchers released hundreds of ping pong ball-like devices called hail sondes into the tempests' path to track the life cycle of a hail stone — when it is melting and freezing, and how wind dynamics that lift and drop these chunks of ice affect their growth.
Convective thunderstorms, with big internal up drafts, generate hail by circulating a mix of water and ice crystals into the freezing layers of the upper atmosphere.
Hail typically forms at altitudes of 20,000 feet to 50,000 feet (6km to 15.24km), where temperatures are between minus 22 degrees Fahrenheit and 14 degrees Fahrenheit (-30 C to -10 C).
Those same up drafts sweep hail sondes into the hail-generating parts of each storm.
'If we can track that sensor with time, we're going to, at least for a couple of these storms, understand the exact path, the exact trajectory that a hailstone takes,' Victor Gensini, a professor of meteorology at Northern Illinois University and an ICECHIP principal investigator, said.
In an atmosphere warmed by climate change, 'we get a lot more instability', Gensini said, which researchers think creates stronger up drafts.
Those stronger up drafts can support larger hailstones for more time, which allows balls or discs of ice to gain mass, before gravity sends them racing to the ground.
'It's kind of like if you take a hair dryer and turn it on its end, it's pretty easy to balance a ping pong ball, right, in that airstream,' Gensini said.
'But what would you need to balance a softball? You would need a much stronger up draft stream.'
Storm modelling suggests stronger up drafts will increase the frequency of large hail in the future, even as it decreases the likelihood of hail overall.
Researchers suspect small hail will decrease because its lower mass means that it will take longer to fall.
By the time it's close to the surface, it has often melted down to water.
'There's this kind of dichotomy, right, where you get less small hail but more large hail in these warmer atmospheres that have very strong up drafts,' Gensini said.
During their field campaign, the researchers amassed a collection of more than 10,000 hailstones in chests of dry ice to try to determine if their computer models are getting the dynamics of hail growth right.
'The hail record is kind of messy,' Gensini said of previous data, adding that observers have recorded more 2-, 3- and 4-inch (5cm to 10cm) hailstones, but it's not clear if that's because more people are chasing and finding big hail or because the atmosphere is producing more of it.
Gensini said the new measurements will help researchers compare what is happening in the air to what they're finding on the ground, which should improve hail forecasts and mitigate economic losses.
In many of the areas where ICECHIP is working, there's a lot of agriculture, according to Karen Kosiba, an atmospheric scientist with the University of Illinois Flexible Array of Radars and Mesonets team who is also working with ICECHIP.
'It affects their crops, their machinery, getting stuff into shelter,' she said. 'There's a lot of economic ties to the weather.'
The future
The National Science Foundation funded ICECHIP's fieldwork, which was approved last fall before President Joe Biden left office. The future of the agency's research isn't clear.
The Trump administration proposed a 57 per cent budget cut to NSF's budget, according to a budget request for fiscal year 2026. The House and Senate appropriations committees will ultimately decide the agency's budget, and both have previewed smaller cuts in early deliberations.
In a statement, the White House pledged to provide 'gold standard research and data for the American People', and referred any questions about NSF's funding to the Office of Management and Budget.
OMB did not immediately respond to a request for comment.
Gensini said federal investments in field research are necessary to propel basic science research projects like ICECHIP at a time when climate change intensifies severe weather.
Without federal funding 'there's going to be no improvement in forecasts', Gensini said.
'There's going to be no way for us to be able to detect whether or not this hailstorm is producing large hail or small hail. Our lab is outside.'