September to December (SOND) constitutes an important rainfall season over the equatorial sector of the Greater Horn of Africa (GHA) region. The regional consensus climate outlook for the September to December 2015 rainfall season indicates increased likelihood of above normal to near normal rainfall over most of the equatorial parts of the GHA. Increased likelihood of near to below normal is indicated over much of the northern sector.
The key factors expected to influence the evolution of the regional climate during the SOND 2015 rainfall season include the Sea Surface Temperature (SST) anomalies over the tropical Oceans and their implications on rainfall bearing mechanisms including (i) the phase and strength of Indian Ocean Dipole mode (IOD) which is currently positive; (ii) likely impacts of current El Niño event over the tropical Pacific that is expected to persist during the rest of 2015 and early months of 2016; (iii) SST anomalies over the Atlantic Ocean. The influence of these ocean processes will be modulated by regional circulation processes, topography and large inland water bodies.