Evaluation of Seasonal Weather Forecasting Accuracy in the Niger Delta Region

Accurate seasonal weather forecasting is vital for planning across agriculture, oil and gas operations, and disaster risk management in Nigeria's South South geopolitical zone. This study evaluates the accuracy of NiMet seasonal rainfall prediction products over the Niger Delta region, comparing official seasonal outlook forecasts with observed rainfall data recorded at meteorological stations in Rivers, Delta, and Bayelsa states from 2020 to 2023. Verification metrics including the Heidke Skill Score, bias score, and percentage correct were applied to assess forecast performance across three rainfall categories: below normal, normal, and above normal. Additional qualitative data were gathered through interviews with 40 NiMet field officers and agricultural extension agents on the practical utility of forecast products. Results show that forecast skill is highest for the above-normal rainfall category and weakest for below-normal predictions, with overall Heidke Skill Scores averaging 0.34, indicating modest but positive skill. Forecast accuracy exhibits significant spatial heterogeneity, with coastal stations demonstrating lower skill than inland stations, attributed to complex mesoscale convective interactions over the Gulf of Guinea. The study recommends investment in high-resolution regional climate model downscaling and strengthening the co-production of user-tailored forecast products. These findings contribute to improving forecast service delivery in one of Nigeria's most climatically sensitive and economically significant regions. Keywords: seasonal forecast, forecast verification, Niger Delta, NiMet, skill score.