Providing early warnings of rainy season onset in East Africa

New research by Oxford University’s Dr Dave MacLeod explores ECMWF’s (European Centre for Medium-Range Weather Forecasts) long-lead forecasts for East Africa.

The timing of the onset of the rains is crucial for a successful harvest. Sowing must be completed before the rains and an unusually early season puts pressure on planting activities. On the other hand, already-planted seeds are compromised if the rains are delayed. Early warning of onset allows farmers to better plan their activities and manage risks.

For a long time farmers in Africa have listed early warning of anomalous onset and cessation of the rains as a key need, and national weather centers are beginning to provide this information in their seasonal outlooks. However, the ability of these outlooks to predict this kind of information is entirely unknown. Without this assessment it is difficult to trust these forecasts.

To help build this trust, the ability of seasonal climate forecasts to predict onset and cessation has been assessed and described in a new paper authored by Oxford University’s Dr Dave MacLeod, recently published in Weather and Climate Extremes.

The results are positive, with analysis showing that these kind of forecasts do indeed provide informative early warning of the timing of the rains for East Africa. But there are some regions where the forecasts work better than others, and the two seasons of east Africa have quite different predictability characteristics. This has important implications for when users can rely on the operational forecasts provided.

The work has been carried out as part of the project ForPAc: Toward Forecast-based Preparedness Action. Here, researchers from the Universities of Oxford and elsewhere in the UK are collaborating with scientists and humanitarian actors in Kenya to explore the potential for utilizing forecasts from day to season ahead, in order to mitigate risks from flood and drought hazards.