Ethiopia: Summary of seasonal outlooks, as of October 2016

The following is a summary of information provided by the Ethiopian National Meteorological Agency (NMA) and the UK Met Office, on the current sea surface temperature in the tropical Pacific Ocean and the Indian Ocean Dipole (IOD) and potential impact on Ethiopia’s weather conditions in coming months.

Indian Ocean Dipole and potential La Niña

“The tropical Pacific Ocean is currently in a neutral El Niño-Southern Oscillation (ENSO) state. Sea surface temperatures (SST) in the central tropical Pacific Ocean are within the neutral range, but remain cooler than average. There is still potential for La Niña (55-60%) to emerge in the remaining months of the year, but if an event does develop, it is unlikely to be strong.

A negative Indian Ocean Dipole (IOD) continues in the Indian Ocean. The current event peaked in July as the strongest negative IOD in at least 50 years. This pattern of SST anomalies is likely to persist through the rest of the Boreal autumn, with the majority of climate models suggesting the negative phase could last until the end of the Boreal winter, albeit as a weakening feature. A negative IOD is typically associated with below-average rainfall and drought across East Africa during the Short Rains (September to November), including southern and eastern parts of Ethiopia.”

The bega season (October to January) is usually associated with dry weather in central and northern Ethiopia, and rain in the South. A negative IOD typically increases the probability of drier-than-average conditions.

According to the NMA forecast map included here, between October and January, normal to above normal rainfall is expected over most of the western and southwestern parts of the country, while normal to below-normal rainfall is anticipated across northern, northeastern, central and eastern parts of the country. Similarly, normal to below-normal rainfall may prevail across the southern and southeastern regions.

Potential humanitarian impact

From a potential humanitarian scenario perspective, this means that there could be a likely impact on the bega in the southern and southeastern regions, which may negatively affect availability of drinking water, pasture and liveand eastern parts of the country. Similarly, normal to below-normal rainfall may prevail across the southern and southeastern regions.

However, “forecasts for averages over long periods cannot provide details about short spells of weather during the period. Thus even in wetter-than-average seasons dry spells may still occur and lead to significant local impacts; flash flooding events are still possible in overall drier-than-average seasons.”