Abstract This study assesses the ability of eight High-Resolution Model Intercomparison Project (HighResMIP) simulations within the Coupled Model Intercomparison Project (CMIP) Phase 6 (CMIP6) to simulate West African rainfall from 1983 to 2014. Using multiple observational datasets, we assess the annual cycle, interannual variability, summer monsoon precipitation (June-July-August-September, JJAS), and extreme rainfall behaviour across the Sahel, the Guinea Coast, and the entire West African region. While the models capture the broad spatial contrast between the wetter Guinea Coast and the drier Sahel, substantial differences persist in their representation of seasonal timing, rainfall magnitude, and extremes. Several models reproduce the observed single August rainfall peak, but others generate bimodal structures or exhibit systematic wet or dry biases. HiRAM most accurately reproduces interannual variability, whereas INM-CM5 and BCC-CSM2 show large structural biases. Model performance reduces when evaluated over the full West African domain, and outliers in JJAS rainfall contribute to pronounced wet biases and uncertainty in extreme precipitation indices. The ensemble mean generally reduces individual model errors but inherits structural deficiencies from poorly performing models, particularly over the Guinea Coast. The results highlight persistent challenges in representing monsoon dynamics, convection, and regional climate drivers, demonstrating that higher spatial resolution alone does not eliminate major biases. Overall, the study highlights the importance of evaluating against multiple observational datasets and emphasises the need for further investigation into the physical processes and regional downscaling approaches necessary to enhance rainfall simulations over West Africa.
Yamoah et al. (Wed,) studied this question.