Moving Target: ENSO and Seasonal Forecasting for the Winter Monsoon over the Western Maritime Continent

Abstract:

The El Niño-Southern Oscillation (ENSO) is the dominant mode of interannual variability over most of the tropics, and the performance of seasonal forecast models over such region is often related to how well they capture the regional teleconnection with ENSO. During the boreal winter monsoon, mean precipitation over much of the Maritime Continent is strongly correlated with ENSO phase. Over these regions, the prospect of accurate seasonal precipitation forecast is optimistic. Unfortunately, the ENSO signal in precipitation is known to be much weaker over the western Maritime Continent, which covers the Malay Peninsula, Borneo, Sumatra, and west Java. We investigate the ENSO teleconnection with mean precipitation using simple statistics on merged observation-remote sensing and model hindcast products. These diagnostics suggest an additional reason for why the winter monsoon mean precipitation over the western Maritime Continent is poorly correlated with the ENSO phase, and why some forecast models may not reflect this observed situation. We make recommendations for some process-based forecast products that are desirable for the Western Maritime Continent.