Measuring Hailstone Trajectories with the HailSonde

The size, shape and ground-impact location of each hailstone is characterised by its trajectory through the parent hailstorm. This trajectory determines whether the hailstone passes through regions of the storm that are more favorable for growth or even miss out entirely. Recent simulation-based studies have demonstrated the diversity of trajectories and how certain pathways exist in response to storm processes. Hail trajectories can also be simulated from radar observations, and this has been shown to significantly improve the accuracy of the estimated ground hail swath for case studies. Operational hail analysis techniques currently do not consider trajectories, leaving a degree of uncertainty when estimating ground impact. The lack of robust observational datasets to verify trajectories is one factor that limits the transition of this new science into operations.

This talk will introduce an innovative approach to measuring trajectories within a hailstorm using hailstone-shaped probes called “HailSondes”. Improvements in low-energy radio, energy storage and electronics miniaturization are combined to make this new sensor possible, which, until recently, was the realm of fantasy for meteorologists. HailSonde measurements will provide critical validation for the practical application radar-derived trajectories for hailstorm analysis and nowcasting, supporting the transition to future hail services and benefiting a wide range of sectors from aviation, risk management, transport and public safety. The design challenges, simulations, prototype development and deployment of HailSondes within field experiments are discussed.