16-18 August 2000, Kisumu, Kenya.
SUMMARY
There is increased likelihood of near-normal to below-normal rainfall over most of the Greater Horn of Africa subregion for the period September-December 2000. However, over western Tanzania, Rwanda, Burundi, western Uganda, southern and south-eastern Sudan, northern and western Ethiopia, southern Eritrea, north-eastern Tanzania and central and south-eastern Kenya there is likelihood of near-normal to above-normal rainfall. High likelihood of above-normal rainfall is indicated over the Red Sea coastal areas of Sudan and much of Eritrea.
It should be recalled that some parts of the sub-region have experienced drought conditions for the past several seasons. In some of these areas the accumulated rainfall deficits may not be offset even if normal rainfall conditions are realized.
This Outlook is relevant only for seasonal time scales and relatively large areas; local and month-to-month variations may occur. Any changes in the patterns of sea surface temperatures (SSTs) over the next few weeks would affect the outlook in some areas. Updates of the outlooks therefore will be provided by the Drought Monitoring Centre, Nairobi (DMCN) and the National Meteorological Services (NMSs) in their respective countries. The users are strongly advised to contact the NMSs for interpretation of this Outlook, finer details, updates and additional guidance.
THE CLIMATE OUTLOOK FORUM
From 16 to18 August 2000, the sixth Climate Outlook Forum was convened in Kisumu, Kenya by the DMCN to formulate consensus guidance for the September-December 2000 season in the Greater Horn of Africa (sometimes referred to as the eastern Africa sub-region, comprising Burundi, Djibouti, Eritrea, Ethiopia, Kenya, Rwanda, Somalia, Sudan, Tanzania and Uganda). Potential users were active participants in the forum. They helped develop the Outlook and assisted in identifying the implications for respective countries and sectors. The Forum reviewed the state of the global climate system and its implications for this subregion. Among the principal factors taken into account was the decaying La Niña episode in the tropical Pacific, and near-average sea-surface temperatures over much of the tropical Indian Ocean.
METHODOLOGY
The forum examined the decaying 1998-2000 La Niña episode and also the SST anomalies over the Indian and Atlantic oceans together with other factors that affect the climate of the sub-region. These were assessed using coupled ocean-atmosphere models, physically based statistical models and expert interpretation. The current status of seasonal-to-interannual forecasting allows prediction of spatial and temporal averages, and may not fully account for all 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 centered around the climatological median; below-normal rainfall as within the driest third of rainfall amounts.
OUTLOOK
September to December constitutes an important rainfall season over the Greater Horn of Africa sub-region. The rainfall outlook for each zone within this sub-region is given below.
Zone I: (northern and western Sudan) Increased likelihood of near-normal to below-normal rainfall.
Zone II:(Red Sea coastal area of Sudan and Eritrea) High likelihood of above-normal rainfall.
Zone III: (western Tanzania, Rwanda, Burundi, western Uganda, southern and south-eastern Sudan, northern and western Ethiopia and southern Eritrea) Increased likelihood of near-normal to above-normal rainfall.
Zone IV: (Djibouti, central and southern Ethiopia, Somalia, south-eastern corner of Sudan, northern and eastern Kenya) Increased likelihood of below normal rainfall. It should be noted that the outlook for Somalia is based on the global model predictions and extrapolations from neighboring countries.
Zone V: (north-eastern Tanzania and central and south-eastern Kenya) Increased likelihood of near-normal to above-normal rainfall.
Zone VI: (north-western and eastern parts of Tanzania, western Kenya and eastern Uganda) Increased likelihood of near-normal to below-normal rainfall.
Zone VII: (central and south-western Tanzania) Increased likelihood of below normal rainfall.
These zones are shown on the attached map.
MAP CAPTION
The numbers for each zone indicate the probabilities 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 for the below-normal. In the case of northern and western Sudan (Zone I) for example, there is 15% probability for rainfall occurring in the above-normal category; a 45% probability for rainfall in the near-normal category; and a 40% probability for below-normal category. It is emphasized that boundaries between sub-regions should be considered as transition zones.
CONTRIBUTORS
The Sixth Climate Outlook Forum was organized jointly by DMCN, International Research Institute for Climate Prediction (IRI), and the World Meteorological Organization (WMO) 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 forecast included representatives of Meteorological Services from nine countries (Institut Géographique du Burundi; Météorologie Nationale de Djibouti; Eritrean Meteorological Services; National Meteorological Services Agency of Ethiopia; Kenya Meteorological Department; Rwanda Meteorological Service; Sudan Meteorological Authority; Tanzania Meteorological Agency; Uganda Meteorological Department) and climate scientists and other experts from national, regional and international institutions and organizations (Drought Monitoring Centre, Nairobi; Drought Monitoring Centre, Harare; IRI; WMO; The UK Met. Office; National Centers for Environmental Prediction and the United Nations Environmental Programme). Additional input was supplied by the European Centre for Medium-Range Weather Forecasts and North Carolina State University.