Seasonal forecast

Seasonal forecast of rainfall over Brazil

At FUNCEME, Fortaleza, we have used DREAM to perform seasonal predicitons. The model has recently been extended to include a basic representation of deep convection and an empirical transfer function to simulate the effects of tropical SST anomalies as sources of diabatic heating.

We have made hindcast predictions for every year since 1982. Each year is initialised with 38 different initial conditions and run from the first of January to the end of May. Observed SST anomalies (SSTAs) are used over the tropical oceans to drive atmospheric convection which in turn influences continental hydrology. The model-generated ensemble mean precipitation correlates well with observed anomalies, both for persisted and developing SSTAs.

Our prediction for the 2022 rainy season is anomalously wet over most of the continent, and particularly over the Northeast. This is consistent with the current La Nina and with most GCM forecasts.

The following plots show ensemble-mean accumulated precipitation over three months (mm). The anomaly is plotted relative to the mean of all hindcasts, to indicate areas of unusually wet (blue) or dry (orange) conditions as predicted by DREAM. Predictions are grouped into running trimesters: Jan-Feb-Mar, Feb-Mar-Apr and Mar-Apr-May.