Precipitation Variability and Predictability over Central Southwest Asia and Southern Africa During Boreal Winter

The Northern Hemisphere winter is the main wet season for Central Southwest Asia (CSWA), and Southern Africa (SF monsoon), where precipitation variability and predictability are limited or understudied. This research focuses on improving our understanding of these regions' wet-season precipitation characteristics and predictability. First, we identify key tropical and extratropical forcings that explain about 75% of winter precipitation variability in CSWA. Tropical forcing comes from an indirect ENSO forcing pathway, the dominant mode of precipitation variability in the Indian Ocean referred to as the Indian Ocean Precipitation Dipole (IOPD). Extratropical forcing arises from a large-scale mode due to internal atmospheric variability. Seasonal forecasting systems effectively depict the characteristics of tropical forcing and its teleconnection with CSWA. Extratropical forcing spatial structure has also been skillfully represented. However, a lack of skill is noted in depicting its interannual seasonal variability and teleconnection with CSWA, which is the main driver of limited prediction skills in models. Second, we develop an empirical model using ENSO, Indian Ocean Dipole (IOD), and IOPD as precursors to investigate SF monsoon variability and predictability. A reasonable skill in predicting SF monsoon precipitation can be achieved by preconditioning these modes as early as five months before the monsoon season. Seasonal forecasting systems that represent the interplay of these modes can achieve reasonable prediction skills over SF with a one to three-month lead. However, ENSO forcing is overly strong in these models, making their predictions less skillful than the empirical model. These findings offer invaluable insight into the mechanisms of global teleconnections within the investigated regions, which should enhance the ability to predict wet season precipitation more accurately.