Hail trajectories under climate change: disentangling the roles of moisture, melting level and updraft kinematics

Large hail is expected to become more frequent under climate change. However, uncertainties remain because storm dynamics and hail formation are imperfectly captured by environmental hail proxies and in convection-permitting models, which are the two most frequently used approaches. We address this using a nonspherical hail-trajectory model in an ensemble of 171 idealized cloud model simulations. Melting level, cloud water, updraft intensity, and updraft width are varied independently. The results largely confirm previous work: rising melting levels (+3-K warming) reduce hail size spectra via enhanced melting and shorter residence times, but increased cloud water dominates, yielding a 30-40% rise in >2-cm hail and 25% larger hail area. However, changes in updraft intensity/width exert stronger, non-monotonic effects, underscoring critical uncertainties and the need to integrate storm structure and robust hail diagnostics in future research.