The affect of the base rate on the extreme dependency score

The Extreme Dependency Score (EDS) has been introduced in the verification of rare events because it does not vanish as other standard scores do. The EDS can be written as a function of the base rate and the hit rate. This paper analyses its dependency on the base rate. It is also shown how the score encourages hedging. Guidelines are provided to make proper use of the EDS when verifying the performance of a forecasting system. Copyright © 2009 Royal Meteorological Society