Intraseasonal Predictions for the South American Rainfall Dipole

The South American rainfall Dipole (SAD) is a renowned spatial structure present in the austral summer as part of the South American monsoon system. SAD phases have been related with extreme precipitations and severe droughts across South America, but are yet to be predicted. Here, we reveal two robust and reliable intraseasonal windows in the accumulated SAD index where we can forecast its quantile-state between 5 to 15 and 60 to 70 days in advance (99% significance level). These windows are insensitive to variations in the pole's size and accumulation window, and results are consistent across different quantiles states (median, tercile, and quartile). Our method, which is based on analyzing the lagged mutual information between future and present states, could be used in the development of early warnings for extreme rainfall events. Moreover, it is unrestricted to the present analysis, being applicable to other stationary signals where a forecast is missing.