Assessing the Skill and Reliability of Seasonal Climate Forecasts in Sahelian West Africa

Abstract

Seasonal climate forecasts have the potential to support planning decisions and provide advanced warning to government, industry, and communities to help reduce the impacts of adverse climatic conditions. Assessing the reliability of seasonal forecasts, generated using different models and methods, is essential to ensure their appropriate interpretation and use. Here we assess the reliability of forecasts for seasonal total precipitation in Sahelian West Africa, a region of high year-to-year climate variability. Through digitizing forecasts issued from the regional climate outlook forum in West Africa known as Prévisions Climatiques Saisonnières en Afrique Soudano-Sahélienne (PRESASS), we assess their reliability by comparing them to the Climate Hazards Group Infrared Precipitation with Stations (CHIRPS) project observational data over the past 20 years. The PRESASS forecasts show positive skill and reliability, but a bias toward lower forecast probabilities in the below-normal precipitation category. In addition, we assess the reliability of seasonal precipitation forecasts for the same region using available global dynamical forecast models. We find all models have positive skill and reliability, but this varies geographically. On average, NCEP’s CFS and ECMWF’s SEAS5 systems show greater skill and reliability than the Met Office’s GloSea5, and in turn than Météo-France’s Sys5, but one key caveat is that model performance might depend on the meteorological situation. We discuss the potential for improving use of dynamical model forecasts in the regional climate outlook forums, to improve the reliability of seasonal forecasts in the region and the objectivity of the seasonal forecasting process used in the PRESASS regional climate outlook forum.

Wet season rainfall onset and flash drought: The case of the northern Australian wet season

“…An estimated 50–60% of the world's population is impacted by the global monsoon system (Yancheva et al ., 2007; Wang and Ding, 2008; Qiao et al ., 2012). Variability in timing of the monsoonal rains has a significant impact on agriculture and economies across monsoonal climates (Fitzpatrick et al ., 2015; Pradhan et al ., 2017; MacLeod, 2018; Parija, 2018; Bliefernicht et al ., 2019; Ali et al ., 2020; Lisonbee et al ., 2020; Pirret et al ., 2020). In many respects, delayed onsets, low seasonal precipitation totals, or prolonged breaks in monsoon precipitation can be considered a drought.…”

Performance of the Global Forecast System's medium-range precipitation forecasts in the Niger river basin using multiple satellite-based products

“…Several studies have investigated the accuracy of seasonal forecasts in West Africa (e.g., Bliefernicht et al, 2019;Pirret et al, 2020). Seasonal forecasts are important for water resource planning, while medium-range (1 to 15 d) forecasts are important for operational decisions, such as reservoir operations.…”

Performance of the Global Forecast System's Medium-Range Precipitation Forecasts in the Niger River Basin

“…Several studies have investigated the accuracy of seasonal forecasts in West Africa (e.g., Bliefernicht et al 2019;Pirret et al 2020). Seasonal forecasts are important for water resource planning, while medium-range (1-day to 15day) forecasts are important for operational decisions, such as reservoir operations.…”