Statement from the Ninth Climate Outlook Forum for the Greater Horn of Africa18--21 February 2002, Eldoret, Kenya
Summary
There is increased likelihood of near-normal to above-normal rainfall over northern Tanzania, Rwanda, Burundi, much of Uganda and Kenya as well as Somalia, eastern half of Ethiopia, southern Djibouti, extreme southern and central Sudan and western Eritrea for the period March to May 2002. However, probabilities are favouring normal to below-normal rainfall over southern Tanzania, northern coast of Kenya and southern coast of Somalia, northeastern Uganda, northwestern Kenya and western Ethiopia as well as the northern parts of southern Sudan. It is recalled that some of these areas have experienced drought conditions for the past several seasons. Below normal rainfall conditions are again, more likely for some of these areas. The impacts of the accumulated rainfall deficits may therefore be exacerbated.
The outlook is relevant only for seasonal time scales and relatively large areas. Local and month-to-month variations may occur. Global Ocean model outputs indicate that there is potential for an El Niño to develop. However, this development will be clearer towards the end of the forecast period. Slightly warmer than normal sea surface temperatures have been noted over the northwestern Indian Ocean. On the other hand, cooler than normal sea surface temperatures have been observed over parts of the southwestern Indian ocean. It should be noted that any occurrence of a tropical cyclone within the forecast period may influence rainfall patterns in the sub region.
Update forecasts are provided by the National weather services and the DMCN. 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 18 to 21 February 2002, the ninth Climate Outlook Forum was convened in Eldoret, Kenya by the Drought Monitoring Centre, Nairobi (DMCN) to formulate consensus guidance for the March to May 2002 rainfall season in the eastern Africa sub region comprising of Burundi, Djibouti, Eritrea, Ethiopia, Kenya, Rwanda, Somalia, Sudan, Tanzania and Uganda (sometimes referred to as the Greater Horn of Africa),. Users from water resources, health, livestock, and agriculture, among other sectors were active participants in the forum. They helped to develop the outlook and assisted in identifying the implications for the 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 much of 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 (see map).
Zone I: Increased likelihood of near normal to below normal rainfall over southern Tanzania.
Zone II: Increased likelihood of near to above-normal rainfall over northern Tanzania, Burundi, Rwanda, much of Uganda and Kenya as well as Somalia, central and eastern Ethiopia, southern Djibouti, the highland and northeastern parts of Eritrea and central Sudan.
Zone III: Increased likelihood of near to below-normal rainfall over northern coast of Kenya and southern coast of Somalia.
Zone IV: Increased likelihood of near to below-normal rainfall over northeastern and eastern Uganda, northwestern and parts of the Lake Victoria basin of Kenya, western Ethiopia as well as the northern parts of southern Sudan.
Zone V: Climatology is suggested over northern Djibouti and southeastern parts of Eritrea.
Zone VI: Climatology is also expected over northern Sudan and western Eritrea.
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 Tanzania (zone I), there is 25% probability of rainfall occurring in the above normal category; 40% probability of rainfall occurring in the near-normal category; and 35% probability of rainfall occurring in the below normal category. It is emphasized that boundaries between zones should be considered as transition areas.
Contributors
The ninth climate outlook forum for the Greater Horn of Africa was organised jointly by the Drought Monitoring Centre, Nairobi (DMCN), World Meteorological Organization (WMO) and the International Research Institute for climate prediction (IRI) within the framework of the United States Agency for International Development (USAID) funded project, “Applications of meteorology to the reduction of climate and weather related risks to food security, water resources, and health for sustainable development in the Greater Horn of Africa sub-region”.
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 Service; Somalia Republic, Sudan Meteorological Authority; Tanzania Meteorological Agency and Uganda Department of Meteorology) and climate scientists and other experts from national, regional and international institutions and organizations (Drought Monitoring Centre, Nairobi; Drought Monitoring Centre, Harare; IRI; WMO; ACMAD, National Centers for Environmental Prediction/Climate Prediction Center (NCEP/CPC), Moi University, Yemen Ministry of Agriculture and Irrigation and University of Nairobi).