Statement from the Fifteenth Climate Outlook Forum for the Greater Horn of Africa

2 to 4 March 2005, Mombasa, Kenya

Summary

Consensus outlook derived from prediction models from ICPAC and other climate centres indicate that there is increased likelihood of near to below normal rainfall over much of the Greater Horn of Africa during the period March to May 2005. However probabilities of near normal to above normal rainfall favour central and northern Tanzania; Burundi; Rwanda; southern Uganda; central and southern Kenya eastern Djibouti; northeastern and western Ethiopia as well as eastern Sudan. It should be noted that episodic intense short rainfall events may occur even in areas with a likelihood of near to below normal rainfall.

The outlook is relevant only for seasonal time scales and relatively large areas. Local and month-to-month variations may occur. Forecast model outputs indicate transition from mild El Niño to neutral conditions over the equatorial Pacific Ocean during the forecast period. The current sea surface temperature (SST) anomalies over much of Atlantic and southwestern Indian Oceans are warmer than average while southern central Atlantic and southeastern Indian Oceans are dominated by cooler than average SSTs. It should be noted that development of tropical cyclones in the Indian Ocean during March - May period may influence the rainfall patterns in the sub-region.

Update forecasts are provided by the National Weather Services and the IGAD Climate Prediction and Applications Centre (ICPAC). The users are therefore strongly advised to keep in contact with their National Meteorological Services for interpretation of this outlook, finer details, updates and additional guidance.

The Climate Outlook Forum

From 2 to 4 March 2005, the fifteenth Climate Outlook Forum was convened in Mombasa, Kenya by the ICPAC to formulate consensus guidance for the March to May rainfall season in the eastern Africa sub-region (sometimes referred to as the Greater Horn of Africa) comprising of Burundi, Djibouti, Eritrea, Ethiopia, Kenya, Rwanda, Somalia, Sudan, Tanzania and Uganda. Users from marine and fisheries management, food security, media, among other sectors were active participants in the forum. They participated in the development of the outlook and formulated the implications of the outlook for their respective countries and sectors. The forum reviewed the state of the global climate system and its implications for the sub-region. Among the principal factors taken into account were the observed and predicted SSTs in the tropical Pacific Ocean, and over the tropical Atlantic and Indian Oceans.

Methodology

The forum examined the current and expected SST anomalies over the Pacific Ocean as well as the Indian and Atlantic Oceans together with other factors that affect the climate of the sub-region. These factors were assessed using coupled ocean-atmosphere models, statistical models and expert interpretation. The current status of seasonal to inter-annual forecasting allows prediction of spatial and temporal averages and may not fully account for the physical and dynamical factors that influence regional and national climate variability.

The experts established probability distributions to indicate the likelihood of above-, near-, or below-normal rainfall for each zone (see Map). Above-normal rainfall is defined as within the wettest third of recorded rainfall amounts in each zone; near-normal is defined as the third of the recorded rainfall amounts centred around the climatological median; below-normal rainfall as within the driest third of the rainfall amounts. Climatology refers to a situation where any of the three categories have equal chances of occurring.

Outlook

March to May constitutes an important rainfall season over the equatorial parts of the Greater Horn of Africa sub-region. The rainfall outlook for each zone within this sub-region is given below.

Greater Horn of Africa Consensus Climate Outlook for the Period March to May 2005

Zone I: Increased likelihood of near to below-normal rainfall over southern and southwestern Tanzania.

Zone II: Increased likelihood of above to near normal rainfall over central and northern Tanzania; Rwanda; Burundi; southern Uganda as well as central and southern Kenya.

Zone III: Increased likelihood of near to below-normal rainfall over much of Kenya; central and northern Uganda; southern western Sudan; southern and eastern Ethiopia and Somalia.

Zone IV: Increased likelihood of near to above- normal rainfall over eastern Djibouti, western Ethiopia and parts of eastern Sudan.

Zone V: Increased likelihood of near to below normal rainfall over northwestern Ethiopia and southwestern Eritrea.

Zone VI: Climatology is indicated over northern Sudan; much of Eritrea and western Djibouti.

Note:

The numbers for each zone indicate the probabilities (chances of occurrence) of rainfall in each of the three categories, above-, near-, and below normal. The top number indicates the probability of rainfall occurring in the above-normal category; the middle number is for the near normal and the bottom number for the below-normal category. For example, in case of southern and southwestern Tanzania (zone I), there is 35% probability of rainfall occurring in the below normal category; 40% probability of rainfall occurring in the near-normal category; and 25% probability of rainfall occurring in the below normal category. It is emphasised that boundaries between zones should be considered as transition areas.

Contributors

The fifteenth climate outlook forum for the Greater Horn of Africa was organised jointly by the IGAD Climate Prediction and Applications Centre, Nairobi (ICPAC), National Meteorological and Hydrological Services (NMHSs), the World Meteorological Organisation (WMO) and the International Research Institute for climate prediction (IRI) within the framework of the United States Agency for International Development (USAID) funded project “Sustainable generation and application of climate information, products and services for disaster preparedness and sustainable development in the Greater Horn of Africa”.

Contributors to this consensus climate outlook included representatives of the Meteorological Services from ten GHA countries (Insititut Geographique du Burundi; Meteorologie Nationale de Djibouti; Eritrea Meteorological Services; National Meteorological Services Agency of Ethiopia; Kenya Meteorological Department; Rwanda Meteorological Services; Somalia meteorological services, Sudan Meteorological Authority; Tanzania Meteorological Agency and Uganda Department of Meteorology) and climate scientists as well as other experts from national, regional and international institutions and organisations (IGAD Climate Prediction and Applications Centre; Drought Monitoring Centre, Harare; International Research Institute for Climate Prediction (IRI); World Meteorological Organisation (WMO); USGS/FEWS-NET; University of Nairobi). Additional input was supplied by the National Centers for Environmental Prediction/Climate Prediction Center (NCEP/CPC), UK. Met Office, and the European Centre for Medium Range Weather Forecasts (ECMWRF).