2012 Chapters (Layout Features)

International Research Institute for Climate and Society

Mason, S. J.

The purpose of this document 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 (NMHSs) and other forecasting centres. The recommendations are meant to complement the WMO’s Commission for Basic Systems (CBS) Standardized Verification System for Long-Range Forecasts (SVSLRF), which has the specific objective of providing verification information for Global Producing Centre (GPC) products that are used as inputs to seasonal forecasting processes, including RCOFs. The SVSLRF procedures are targeted at providing information about the quality of ensemble prediction systems. In contrast, the procedures described in this document are targeted at verification of probabilistic forecasts, and have been selected to inform end-users of the forecasts as well as the forecasters themselves. The recommended procedures range in complexity from simple measures for communicating forecast quality to non-specialists, to detailed diagnostic procedures to provide in-depth analyses of the various strengths and weaknesses of forecasts. While the focus of the recommended procedures is on how well the forecasts correspond with the observations (forecast quality), care is taken to measure those attributes that can make forecasts potentially useful (forecast value). Interpretive guides for each of the recommended procedures are included to assist the user in understanding the verification results, and worked examples are included in an appendix. A glossary of technical terms is also provided.