skill
Several simple formulations are commonly used in meteorology. The skill score (SS) is useful for evaluating predictions of temperatures, pressures, or the numerical values of other parameters. It compares a forecaster's root-mean-squared or mean-absolute prediction errors, Ef, over a period of time, with those of a reference technique, Erefr, such as forecasts based entirely on climatology or persistence, which involve no analysis of synoptic weather conditions: If SS > 0, the forecaster or technique is deemed to possess some skill compared to the reference technique. For binary, yes/no kinds of forecasts or detection techniques, the probability of detection (POD), false alarm rate (FAR), and critical success index (CSI) may be useful evaluators. For example, if A is the number of forecasts that rain would occur when it subsequently did occur (forecast = yes, observation = yes), B is the number of forecasts of no rain when rain occurred (no, yes), and C is the number of forecasts of rain when rain did not occur (yes, no), then For perfect forecasting or detection, POD = CSI =1.0 and FAR = 0.0. POD and FAR scores should be presented as a pair.
