Guidance on Verification of Operational Seasonal Climate Forecasts WMO-No.1220

The purpose of this publication is to describe and recommend procedures for the verification of operational probabilistic seasonal forecasts, including those from the Regional Climate Outlook Forums (RCOFs), National Meteorological and Hydrological Services and other forecasting centres. The recommendations are meant to complement the WMO Commission for Basic Systems Standardized Verification System for Long-range Forecasts (SVSLRF). SVSLRF defines standards for verifying model outputs from Global Producing Centres (GPCs), and so includes procedures for measuring the quality of ensemble prediction systems. In contrast, the procedures described in this publication are exclusively for verification of probabilistic forecasts, which may be model outputs, expert subjective assessments, or a combination of both. A second difference from SVSLRF is that procedures described in this publication are concerned not only with verification of a history of forecasts, but also of forecasts for one specific target period – for last year’s RCOF forecast, for example.