Hailstone Trajectory and Surface Hailfall Analysis in the 29-30 May 2012 Kingfisher, OK Supercell

During the Deep Convective Clouds and Chemistry Experiment (DC3), a wealth of data was collected on a hail-producing tornadic supercell near Kingfisher, OK on 29-30 May 2012. Three mobile radars collected radial velocity, reflectivity, and polarimetric data over a ~70- minute period during the storm’s mature phase. Additionally, far-environmental and in-storm soundings were taken following the storm's track while hail samples were collected in the town of Kingfisher, OK by the Insurance Institute for Business and Home Safety (IBHS). The 4-D storm fields of airflow and reflectivity from multi-Doppler radar analyses are combined with 4-D Diabatic Lagrangian Analysis (DLA) retrievals of temperature and water substance and WRF- HAILCAST physics to compute densely spaced Lagrangian hail growth trajectories for the present study. Hail embryos are initialized in the hail growth module every three minutes of the radar analysis period (2251-0000 UTC) to produce over 2.7 million hail trajectories. Using a new, unique dataset we validate previous hail growth trajectory theories and introduce new hypotheses. Hailstone positions within the storm and at the surface are analyzed for hailstones of varying sizes. It is found that severe hailstones spend a majority of their growth phase within the downshear stagnation zone where horizontal winds are have minimal impact on the hailstones. Simulated severe hail is favored over non-severe hail by significantly longer residence times in 30-50 m/s updrafts and supercooled cloud water contents exceeding 5 g/kg. As the storm strengthens, a new trajectory pathway from embryos sourced within the backsheard anvil emerges, which leads to an increase in overall hail production. Simulated hail swaths provide spatial and temporal understanding of hail diameters and concentrations at the surface. The largest hail falls to surface preferentially along the southern (storm-inflow) flank of the hail swath, though size-sorting effects differ along the hail swath. In an effort to improve the hail growth physics, sensitivity tests are conducted on the heat transfer coefficient while hailstones are allowed to be oblate, the ice collection efficiency, and the shedding threshold. The ice collection efficiency showed no sensitives while the shedding threshold showed the greatest sensitivity for the smallest hailstones. Oblate hailstones with increased heat transfer showed the greatest sensitivity. Spherical and oblate hailstones are compared to observations and we conclude the oblate hailstones are more physically representative of what was observed and would occur in nature