Examining Interannual Variability of the Short Rains for Different Categories of Wet and Dry Years

East African "shorts rains" variability has long been a subject of interest both for its complexity and its sometimes dire human impacts. Four large-scale factors are thought to influence the shorts rains: Niño 3.4, the IOZM, and the surface and upper-level zonal winds over the central Indian Ocean. Recent research has shown that these established teleconnections are not as robust as previously thought. Particularly, the relationships between the short rains season and these factors have broken down since 1982, with several seasons having opposite conditions than what was expected. Furthermore, the debate over which large-scale factors have the most effect on the short rains season is on-going. In this study, the relationship between the interannual variability of the short rains and known large-scale forcing factors is examined with the goal of answering three questions: 1) Are the factors associated with dry and wet conditions different before versus after 1982? 2) Why did dry or wet conditions fail to occur when predicted in recent years? 3) Do dry seasons with different combinations of large-scale factors produce different local patterns in atmospheric circulation? To investigate these questions, different October-November seasons were designated into categories. Analysis was done on several diagnostic variables for each category of rainfall seasons. Contrary to what was expected, zonal wind field results showed few differences between pre- and post-1982, giving little answers as to why the relationships between the short rains and these factors has changed since 1982. Omega results highlight influence of a narrow area of upper-level sinking and rising motion over and just off the coast of East Africa. This study suggests that this feature, while indeed connected to the four established links, could shed new insight on the short rains interannual variability if evaluated as an individual factor. Results also reaffirmed prior research that shows wet and dry conditions have different sensitivities to large-scale factors. Additionally, it was found that different combinations of factors, which all produced dry conditions, had different local atmospheric patterns. Some of the greatest contrasts seen in local patterns were between factor combinations that include the IOZM compared to combinations without it. This suggests that different large-scale factors could counteract each other.