Verification measures

• The Brier score - the MSE of probability forecasts
• Decomposition of the Brier score
• The Brier score is a “proper” score
• The Brier skill score
• The rank probability score (RPS)

In contrast to deterministic forecasts, an individual probabilistic forecast can never be “right” or “wrong” except when 0% or 100% have been stated. Probability forecasts can therefore, only be verified from large samples of forecasts.