Weather and climate forecasting, using climate models, have become essential tools and life-savers in the West African region; in spite of the fact that climate models do not fully comply with attributes of forecast qualities—RASAP: reliability, association, skill, accuracy, and precision. The objective of this paper is to quantitatively evaluate, in comparison to CRU and ERA5 datasets, the RASAP compliance-level of the weather@home2 modeling system (w@h2). Findings from some statistical evaluations show that, to a moderately significant extent, w@h2 model provides useful information during the monsoon seasons; skills to capture the Little Dry Season over the Guinea zone; predictive skills for the onset season; ability to reproduce all the annual characteristics of the surface maximum air temperature over the region; as well as skill to detect heat waves that usually ravage West Africa during the boreal spring. The model displays traces of attributes that are needed for seasonal climate predictions and applications. Deficiencies in the quantitative reproducibility point to the facts that the model does provide a reliability akin to that of regional climate models. This paper further furnishes a prospective user with information on whether the model might be “useful or not” for a particular application.

Weather and climate forecasting is extremely important for improving the socio-economic well-being of the West African region. It safe-guards the region from weather and climate related disasters. Hence, utilization of products from climate models are being encouraged and have therefore become essential tools and life-savers, in spite of the fact that climate models do not fully comply with attributes of forecast qualities - RASAP: reliability, association, skill, accuracy and precision. This paper thus quantitatively evaluates, in comparisons to CRU and ERA5 datasets, the RASAP compliance-level of the weather@home2 modelling system (w@h2: a successor to the well-known weather@home1 modelling system) which now produces an exceptionally large number of ensembles of simulations (>10,000). Having been designed for the investigation of the behavior of extreme weather under anthropogenic climate change, findings show that the performance of w@h2 in terms of climate variability may be more relevant than measures of the mean climatology. To some significant extent w@h2 model provides little, if any, predictive information for precipitation during the dry season, but may provide useful information during the monsoon seasons as well as skill to capture the Little Dry Season over the Guinea zone; predictive skills for the onset season suggest that the model is getting processes right. The w@h2 model is also able to reproduce all the annual characteristics of the surface maximum air temperature over the sub-region with skill to detect heat waves that usually ravage West Africa during the boreal spring. With synchronization > 80% the model has the ability to reliably / accurately simulate the actual anomaly signs of the observed climate parameters which is one of the special attributes of a model that is needed for seasonal climate predictions and applications. The large sample sizes produced by the w@h2 model are able to show that sampling quality of the tails of the distribution is no longer the primary constraint / source of uncertainty. The study further furnishes a prospective user with information on whether the model might be “useful or not” for a particular application.