A FRAMEWORK FOR ASSESSING OPERATIONAL MADDEN–JULIAN OSCILLATION FORECASTS: A CLIVAR MJO Working Group Project

The U.S. Climate Variability and Predictability (CLIVAR) MJO Working Group (MJOWG) has taken steps to promote the adoption of a uniform diagnostic and set of skill metrics for analyzing and assessing dynamical forecasts of the MJO. Here we describe the framework and initial implementation of the approach using real-time forecast data from multiple operational numerical weather prediction (NWP) centers. The objectives of this activity are to provide a means to i) quantitatively compare skill of MJO forecasts across operational centers, ii) measure gains in forecast skill over time by a given center and the community as a whole, and iii) facilitate the development of a multimodel forecast of the MJO. The MJO diagnostic is based on extensive deliberations among the MJOWG in conjunction with input from a number of operational centers and makes use of the MJO index of Wheeler and Hendon. This forecast activity has been endorsed by the Working Group on Numerical Experimentation (WGNE), the international body that fosters the development of atmospheric models for NWP and climate studies. The Climate Prediction Center (CPC) within the National Centers for Environmental Prediction (NCEP) is hosting the acquisition of the forecast data, application of the MJO diagnostic, and real-time display of the standardized forecasts. The activity has contributed to the production of 1–2-week operational outlooks at NCEP and activities at other centers. Further enhancements of the diagnostic's implementation, including more extensive analysis, comparison, illustration, and verification of the contributions from the participating centers, will increase the usefulness and application of these forecasts and potentially lead to more skillful predictions of the MJO and indirectly extratropical and other weather variability (e.g., tropical cyclones) influenced by the MJO. The purpose of this article is to inform the larger scientific and operational forecast communities of the MJOWG forecast effort and invite participation from additional operational centers.