The IRI has prepared this experimental Climate Outlook for Africa for August 2001 - January 2002. Of relevance in the preparation of this outlook is the prediction of near-average to slightly warmer than average conditions in the eastern equatorial Pacific for the next 6 to 9 months. Currently the sea surface temperatures (SSTs) across much of the eastern and central equatorial are near their long-term average (SSTs), although slightly lower than average SSTs have developed along the immediate western coast of South America and warmer than average SSTs persist in the extreme western part of the basin. Near neutral equatorial Pacific SST conditions are in effect for the first season of the forecast, August-September-October 2001, September-October-November 2001, October-November-December 2001, while during the second season, November-December 2001-January 2002, they are expected to be slightly above average. The warmer than average SSTs that continue to dominate much of the Indian Ocean are expected to decrease slowly through the forecast period. The area of above-average temperature in the tropical south Atlantic Ocean is expected to persist through at least the first half of the forecast period.

This Outlook was prepared using the following procedures and information:

A) Coupled ocean-atmosphere model predictions of tropical Pacific SST covering the forecast period. Particularly heavy weighting has been given to predictions from the coupled model operated by the NOAA National Centers for Environmental Prediction, Climate Modeling Branch. This model suggests a continuation of near-average conditions during the first forecast season. The forecast for near-neutral conditions is consistent with some, but not all, numerical and statistical forecasts of central and eastern Pacific SSTs.

B) Forecasts of the tropical Indian ocean using a statistical model developed by the IRI.

C) Global atmospheric general circulation model (GCM) predictions of the atmospheric response to the present and predicted sea-surface temperature patterns.

D) Other sources of information include NASA's Seasonal to Interannual Prediction Project (GSFC-NASA).

The procedures, models, and data used to derive this Climate Outlook may be somewhat different from those used by the national meteorological services in the region. Thus, this product may differ from the official forecasts issued in those areas. The Climate Outlook for August 2001 - January 2002 is dependent on the accuracy of the SST predictions. For the tropical Pacific, these predictions can be expected to provide useful information, but there is some uncertainty concerning the evolution of SSTs. Spread (variation) in global SST predictions is a source of uncertainty in the Outlook provided here. In particular, the forecasts for the tropical Indian and Atlantic oceans have been an important influence on the forecasts over Africa. Note that even if perfectly accurate SST forecasts were possible, there would still be uncertainty in the climate forecast due to chaotic internal variability of the atmosphere. These uncertainties are reflected in the probabilities given in the forecast.

It is stressed that the current status of seasonal-to-interannual climate forecasting allows prediction of spatial and temporal averages, and does not fully account for all factors that influence regional and national climate variability. This Outlook is relevant only to seasonal time scales and relatively large areas; local variations should be expected, and variations within the 3-month period should also be expected. For further information concerning this and other guidance products, users are strongly advised to contact their National Meteorological Services.

This Outlook covers four seasons: August-September-October 2001, September-October-November 2001, October-November-December 2001 and November-December 2001-January 2002. Maps are given showing tercile probabilities of precipitation and temperature. The maps for precipitation indicate the probabilities that the seasonal precipitation will fall into the wettest third of the years (top number), the middle third of the years (middle number), or the driest third of the years (bottom number). The color shading indicates the probability of the most dominant tercile -- that is, the tercile having the highest forecast probability. The color bar alongside the map defines these dominant tercile probability levels. The upper side of the color bar shows the colors used for increasingly strong probabilities when the dominant tercile is the above-normal tercile, while the lower side shows likewise for the below-normal tercile. The gray color indicates an enhanced probability for the near-normal tercile (nearly always limited to 40%). As before, numbers and their associated histograms show the probabilities of the three terciles. In areas with lots of spatial detail, there may not be sufficient room on the map, to allow histograms for each region. In those cases, some idea of the probabilities may be gained from the color alone. A qualitative outlook of climatology ("C") indicates that there is no basis for favoring any particular category. Areas that are marked by "D" represent regions experiencing their dry season (less than 15% of annual precipitation) and for which less than 5 cm of precipitation typically occurs over the season. Otherwise, for example, in the case of eastern Ethiopia in August-September-October 2001 (Map A), there is a 25% probability that the precipitation will be in the wettest third of the years, a 35% chance it will be in the near-normal third of the years, and a 40% chance that the precipitation will be in the driest third of the years.

Maps of temperature show expected probabilities that the seasonal temperatures will fall into the warmest third of the years, the middle third of the years, or the coldest third of the years (Map A). The numbers for each region on the temperature maps indicate the probabilities of temperatures to fall in each of the three categories, above-, near-, and below-normal.

Boundaries between sub-regions should be considered as transition zones, and their location considered to be only qualitatively correct.

August-September-October 2001:

The following regions of enhanced probabilities of precipitation anomalies are indicated:

Slightly enhanced probabilities for above normal precipitation (30%-30%-40%) are forecast for coastal Western Sahara and in the vicinity of the Canary Islands.

An enhanced probability for below normal precipitation (45%-35%-20%) is forecast for southwestern Gabon and the coastal portions of the Rupublic of the Congo and Democratic Republic of the Congo. Slightly enhanced probabilities for below normal precipitation (40%-35%-25%) are forecast for the Gulf of Guinea region from southern Liberia to southern Cameroon and extending southward to Gabon and western parts of the Republic of the Congo and the Democratic Republic of the Congo. Slightly enhanced probabilities for below normal precipitation (40%-30%-30%) are forecast for much of the west coast of Angola

Slightly enhanced probabilities for below normal precipitation (40%-35%-25%) are forecast for central and eastern Ethiopia, Djibouti, southern Eritrea, parts of Somalia, southwestern Yemen, and northeastern Kenya

Slightly enhanced probabilities for near normal precipitation (35%-40%-25%) are forecast for central Somalia

Slightly enhanced probabilities for above normal precipitation (25%-35%-40%) are forecast for Indian Ocean - southern edge of Madagascar

Slightly enhanced probabilities for below normal precipitation (40%-35%-25%) are forecast for northern Madagascar and Arc des Comores

The following regions of enhanced probabilities of temperature anomalies are indicated:

The forecast indicates increased probabilities for above-normal temperatures over most of the African continent. Strongest probabilities (15%-30%-55%) are found over the Gulf of Guinea region and throughout the Sahel, extending from Mali to the western edge of Ethiopia and through much of central interior Africa. This region of strongly enhanced probabilities is surrounded by regions of weaker probabilities that also favor above normal temperatures.

Over northern Africa an area of strongly enhanced probabilitsies for above-normal temperatures is forecast over northern Algeria, surrounded by regions of weaker probabilities for above-normal temperatures.

Over southern Africa, enhanced probabilities for above-normal temperature (20%-35%-45%) are found over eastern Botswana, Zimbabwe and southern Mozambique. The region is surrounded by areas of slightly enhanced probabilities of near-normal to above-normal temperatures (20%-40%-40%).

Slightly enhanced probabilities of near-normal temperatures (25%-40%-35%) are forecast for parts of southern Angola, Zambia, and Malawi.

Slightly enhanced probabilities of above-normal temperatures are forecast for southern parts of the Arabian peninsula, including southwestern Saudi Arabia, Yemen, and parts of coastal Oman.

Slightly enhanced probabilities of above-normal temperatures (25%-35%-40%) are forecast over parts of Iran.

September-October-November 2001:

Slightly enhanced probabilities for below normal precipitation (40%-30%-30%) are forecast for coastal parts of Senegal and Mauritania.

Slightly enhanced probabilities for below normal precipitation (40%-30%-30%) are forecast for southeastern Chad, central western Sudan and norhtern Central African Republic.

Slightly enhanced probabilities for below normal precipitation (40%-35%-25%) are forecast for parts of the Gulf of Guinea region including coastal Liberia, Cote D'ivoire and Ghana and also southwestern Cameroon and western Gabon.

Slightly enhanced probabilities for near-normal precipitation (30%-40%-30%) are forecast for parts of eastern Gabon, southern Republic of the Congo, western-most Democratic Republic of the Congo, and northwestern Angola.

Slightly enhanced probabilities of above-normal precipitation is forecast for Iraq, western Iran, eastern Syria, and southeastern Turkey.

An enhanced probability for below normal precipitation (45 35 20) is forecast for parts of northern Kenya, southern Ethiopia, and much of Somalia. Surrounding this region the forecast indicates slightly enhanced probabilities for below-normal precipitation (40%-35%-25%) over central Ethiopia, and parts of Kenya and Somalia.

Slightly enhanced probabilities for near normal precipitation (35%-40%-25%) are forecast for the Seychelles Islands

The following regions of enhanced probabilities of temperature anomalies are indicated:

The forecast indicates strongly enhanced probabilities for above-normal temperatures over most of the African continent. Strongest probabilities (15%-30%-55%) are found over much of the Sahel region, extending from Mali to eastern Sudan and through much of central interior Africa. This region of strongly enhanced probabilities is surrounded by regions of weaker probabilities that also favor above normal temperatures.

Slightly enhanced probabilities for near-normal temperature (30%-40%-30%) are forecast for coastal Western Sahara.

Slightly enhanced probabilities for below normal temperature (40%-35%-25%) are forecast for southwestern Namibia and the northwestern coast of South Africa

Enhanced probabilities for above-normal temperature (25%-30%-45%) are forecast for central Algeria. This region is surrounded by a forecast for slightly enhanced probabilities for above-normal temperature (25%-35%-40%) over much of northern and eastern Algeria.

Strongly enhanced probabilities for above-normal temperature (20%-30%-50%) are forecast for central Saudi Arabia, surrounded by weaker probabilities that favor above-normal temperature extending over the Red Sea region, the Arabian Peninsula, as well as over Iraq and neighboring areas.

Enhanced probabilities for above-normal temperature (20%-35%-45%) are forecast for parts of central and southern Mozambique, surrounded by weaker probabilities that favor above-normal temperature (25%-35%-40%).

October-November-December 2001:

The following regions of enhanced probabilities of precipitation anomalies are indicated:

Slightly enhanced probabilities for above-normal precipitation (25%-35%-40%) are forecast over northeastern corner of Morocco and northwestern Algeria.

Enhanced probabilities for above-normal precipitation (20%-35%-45%) are forecast over parts of western Iran and eastern Iraq. Surrounding this region slightly enhanced probabilities for above-normal precipitation (25%-35%-40%) are forecast.

Slightly enhanced probabilities for above-normal precipitation (20%-35%-45%) are forecast for parts of western Mauritania and coastal Senegal.

Slightly enhanced probabilities for above-normal precipitation (30%-30%-40%) are forecast for eastern Mali.

Slightly enhanced probabilities for below-normal precipitation (40%-35%-25%) are forecast for the eastern Gulf of Guinea region, over coastal Ghana, Nigeria, Cameroon.

Enhanced probabilities for below-normal precipitation (45%-35%-20%) are fpreast pver parts of central Tanzania, surrounded by slightly enhanced probabilities ((40%-35%-25%) forecast for most of the rest of the country and fore southern Kenya, northern Zambia and northwestern Mozambique.

Slightly enhanced probabilities for near-normal to above-normal precipitation (25%-40%-35%) are forecast for Zimbabwe, eastern Botswana and parts of northern South Africa.

Slightly enhanced probabilities for above-normal precipitation (30%-30%-40%) aer forecast for southern Namibia, and western South Africa.

The following regions of enhanced probabilities of temperature anomalies are indicated:

Strongly enhanced probabilities for above-normal temperature (15%-30%-55%) are forecast for many parts of western and central Africa. Surrounding this region are forecasts for weaker probabilities favoring above-normal temperature extending over most of western, northern and central Africa.

Enhanced probabilities for above-normal temperature (20%-35%-45%) ar3e forecast fo western and northern Saudi Arabia extending over the Red Sea region and over parts of Iraq and western Iran. Surrounding this region are slightly enhanced probabilities for above-normal temperature (25%-30%-40%) extending over a large region of northeastern Africa and over much of the Middle East.

Slightly enhanced probabilities for below-normal temperature (40%-35%-20%) over coastal parts of northern Tanzania, Kenya, and southern Somalia.

November-December 2001-January 2002:

The following regions of enhanced probabilities of precipitation anomalies are indicated:

Slightly enhanced probabilities for above-normal precipitation (30%-30%-40%) are forecast for much of Saudi Arabia, Iraq, and parts of Iran.

Slightly enhanced probabilities for near-normal to above-normal precipitation (20%-40%-40%) are forecast for a region in western Africa covering southern Mauritania, southwestern Mali, eastern Senegal, northern Cote D'Ivoire and the western half of Burkina Faso.

Slightly enhanced probabilities for above-normal precipitation (30%-30%-40%) are forecast for parts of northern central Africa extending from Chad to Gabon.

Slightly enhanced probabilities for above-normal precipitation (25%-35%-40%) are forecast for parts of southern Republic of the Congo, southwestern Democratic Republic of the Congo, and northwestern Angola.

Enhanced probabilities for below-normal precipitation (45%-35%-20%) are forecast for much of western Kenya, eastern Uganda, and northern and western Tanzania. The region is surrounded by a larger region with a forecast indicating slightly enhanced probabilities for below-normal precipitation.

Slightly enhanced probabilities for above-normal precipitation (25%-35%-40%) are forecast over northern South Africa, eastern Botswana, southern Mozambique, and much of Zimbabwe.

Slightly enhanced probabilities for below-normal precipitation (40%-30%-30%) are forecast along the southern coast of South Africa.

The following regions of enhanced probabilities of temperature anomalies are indicated:

Strongly enhanced probabilities for above-normal temperature (10%-30%-60%) are forecast over western Tanzania, southwestern Democratic Republic of the Congo and northwestern Zambia. Surrounding this region are weaker but still stongly enhanced probabilities for above-normal temperature through much of central Africa. Enhanced probabilities for above-normal temperature (20%-35%-45%) surround this region and extend westward over Western Africa, surrounded by still weaker probabilities for above-normal temperature throughout the Sahel and across to the Red Sea region.

Enhanced probabilities for above-normal temperature (20%-35%-45%) are forecast for parts of northern Saudi Arabia, northwestern Sudan, and southwestern Iraq. Surrounding this region are slightly enhanced probabilities for above-normal temperature (25%-35%-40%) covering much of the middle east.

Slightly enhanced probabilities for below-normal temperature (40%-35%-25%) are forecast for northeastern Tunisia.

OBSERVED CLIMATOLOGY DATA for Aug-Sep-Oct, Sep-Oct-Nov, Oct-Nov-Dec and Nov-Dec-Jan

CLIMATOLOGICAL AVERAGE: Temperature Precipitation

TERCILE THRESHOLDS (33%-ile & 67%-ile): Temperature Precipitation

EXTREME THRESHOLDS (15%-ile & 85 %-ile): Temperature Precipitation

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