Subseasonal forecasting

This chapter describes the data that are used primarily in subseasonal forecasting of precipitation over West Africa. They include precipitation, outgoing longwave radiation (OLR), brightness temperature, sea surface temperature (SST), and reanalysis, including winds and other derived fields such as velocity potential (VP). The chapter also describes the convectively coupled equatorial waves (CCEWs). It presents other convectively coupled signals, including Kelvin waves, signals between 10 and 25 days, and the Madden-Julian oscillation (MJO). The chapter discusses the operational prediction tools and also describes a step-by-step guideline for operational subseasonal forecasting. One of the challenges of operational subseasonal forecasting is that it involves some degree of subjectivity; it also heavily draws on the forecaster’s experience. The chapter explains one approach, based on the MJO and numerical weather prediction (NWP) guidance. The outlooks can be produced at any operational meteorological centre with access to the MJO and NWP tools.