Observed annual median and trend of the Mean Potential Hail Index (PHI) over the period 1951-2010

Based on the logistic hail model (Mohr, Kunz, and Geyer, 2015) and reanalysis data from NCEP-NCAR (Kalnay, et al., 1996). Trends with significance below the 5% level are cross-hatched. Note that significant trends are only found for values below -5 PHI over the period.