Precipitation Production in a Large Montana Hailstorm: Airflow and Particle Growth Trajectories

Abstract

Abstract Computations of air motion and precipitation growth using winds derived from Doppler radar measurements were analyzed to reveal important flow features that influenced the production of precipitation during the nearly steady phase of a well-observed severe storm in Montana that produced hail as large as 5 cm in diameter. The storm had many features commonly associated with supercells, though it exhibited a gently sloping overhang on its low-level inflow side, rather than the more classical vaulted structure. Formed initially as the right member of a splitting storm pair, it moved slowly eastward while embedded in moderately sheared environmental winds. Characteristic hail growth trajectories and precipitation fallout positions are considered in conjunction with the deduced embryo sources and formation regions. Based on particle growth calculations, measurements by radar and research aircraft, cloud photography and direct hailstone examination, four general sources of hail embryos were apparent: 1...