Table 4 Verification indices based on the terms in Table 3.

Accuracy

\(ACC= \frac{a+d}{a+b+c+d}\)

ACC ϵ [0; 1]

ACC = 1 for a perfect forecast

Bias

\(B= \frac{a+b}{a+c}\)

B > 1, the event is overforecast,

B < 1, the event is underforecast

Probability of detection

\(POD= \frac{a}{a+c}\)

POD ϵ [0; 1]

POD = 1 for a perfect forecast

False alarm ratio

\(FAR= \frac{b}{a+b}\)

FAR ϵ [0; 1]

FAR = 0 for a perfect forecast

Critical success index

\(CSI= \frac{a}{a+b+c}\)

CSI ϵ [0; 1]

CSI = 1 for a perfect forecast