There is a link between the precipitation in the monsoonal season (JAS) in West Africa and the SST of the Atlantic and Indian oceans on interannual time-scale. Therefore, we elaborate a statistical method to predict the intensity of the West Africa monsoon in the Sudan-Sahel region, based on the SSTAs.

The JAS rainfall in the Sudan-Sahel region is well correlated with the SSTA in the Equatorial Atlantic in OND, in the South Atlantic in NDJ, and in the West Indian in JFM. We use these 3 sub-basins as predictors for the JAS amount of the Sudan-Sahel monsoonal rainfall, in a lagged multi-linear regression analysis. The probability of detection (POD) is 1.00 for wet events, 0.67 for normal events and 0.80 for dry events.

The set of predictors becomes fully available within 4 months: in January the SSTA in the Gulf of Guinea, in February the South Atlantic, and in April the West Indian. Therefore we provide the forecast in 3 steps, adding each predictor when it is available, having outlooks in January and February, and the final forecast in April.

Outlook issued in January

Outlook issued in February

Forecast issued in April