Open circles represent reliability of original POSH equation with no population density constraint. Solid black circles represent reliability of original POSH equation when scored only over areas of high population density. Red circles represent reliability of adjusted POSH equation when scored over areas of high population density. At KMLB, the reliability of the POSH parameter improves with increasing population density threshold, and the adjusted POSH equation improves the reliability further. Observed relative frequency is frequency of severe hail observations when POSH equals given value.
Solid line represents perfect reliability.
At KFWS, using the adjusted POSH equation also improves the reliability of the parameter. The following two figures compare the optimum warning threshold with the Warning Threshold Selection Model for the 51 days at Melbourne. The optimum warning threshold is the warning threshold which produces the highest Critical Success Index. Warning threshold as a function of the melting level for 51 days from KMLB, analyzed over entire radar domain. Vertical bars represent the range of warning thresholds which correspond to a CSI within five percentage points of the maximum.