The IRI has prepared this experimental Climate Outlook for Africa for September 2001 - February 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 Pacific are near their long-term average, with locally warm anomalies near the dateline (SSTs), although slightly lower than average SSTs exist in the far eastern equatorial Pacific and warmer than average SSTs persist in the extreme western part of the basin. Near neutral (<0.5C) equatorial Pacific SST conditions are in effect for the first half of the forecast period, September-November 2001, October-December 2001, while during the second half, November-December 2001-January 2002, December 2001-February 2002, they are expected to be slightly above average (approximately 0.5C). 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 Atlantic Ocean has weakened over the last couple months and is predicted to weaken further through the forecast period.

METHODS -

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 September 2001 - February 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 in global SST predictions is a source of uncertainty in the Outlook provided here. 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 season should also be expected. For further information concerning this and other guidance products, users are strongly advised to contact their National Meteorological Services.

OUTLOOK -

This Outlook covers four seasons: September-November 2001, October-December 2001, November-December 2001-January 2002 and December 2001-February 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 right side of the color bar shows the colors used for increasingly strong probabilities when the dominant tercile is the above-normal tercile, while the left 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 5cm of precipitation typically occurs over the season. Otherwise, for example, in the case of central Argentina in September-November 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 in part of eastern and northeastern Brazil.

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.

September-October-November 2001:

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

An enhanced probability for below normal precipitation (45%-35%-20%)is forecast for extreme northern Colombia, surrounded by more weakly enhanced probabilities for below normal precipitation in an additional portion of northern Colombia and in northwestern Venezuela.

Slightly enhanced probabilities for above normal precipitation (25%-35%-40%)are forecast for

Slightly enhanced probabilities for above normal precipitation (25%-35%-40%)are forecast for the southern part of northern Chile, and in northwestern Argentina.

Slightly enhanced probabilities for below normal precipitation (40%-35%-25%) are forecast for a small portion of northeastern Brazil.

Slightly enhanced probabilities for below normal precipitation (40%-35%-25%) are forecast for a portion of southeastern Brazil.

Slightly enhanced probabilities for below normal precipitation (40%-35%-25%) are forecast for central Chile, central Argentina and southern Uruguay.

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

An enhanced probability for above normal temperature (20%-35%-45%) is forecast for part of northern Peru and extreme western Brazil, surrounded by more weakly enhanced probabilities for above normal temperature in most of Ecuador, southern Colombia, an additional part of northern Peru, western Brazil and northern Bolivia.

Slightly enhanced probabilities for near normal temperature (25%-40%-35%) are forecast for northeastern Brazil and some of the surrounding area.

Slightly enhanced probabilities for near normal temperature (25%-40%-35%) are forecast for a portion of southeastern Brazil.

Slightly enhanced probabilities for above normal temperature (25%-35%-40%)are forecast for central and northern Brazil near the mouth of the Amazon.

Slightly enhanced probabilities for above normal temperature (25%-35%-40%)are forecast for a portion of southern Brazil and adjacent eastern Paraguay and extreme northeastern Argentina.

Slightly enhanced probabilities for above normal temperature (25%-35%-40%)are forecast for much of Chile, much of Argentina, and southern Uruguay.

October-November-December 2001:

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

An enhanced probability for below normal precipitation (45%-35%-20%)is forecast for extreme northern Colombia and extreme northwestern Venezuela, surrounded by more weakly enhanced probabilities for below normal precipitation in an addition portion of both countries.

An enhanced probability for above normal precipitation (20%-35%-45%) is forecast for French Guiana and adjacent northern Brazil, surrounded by more weakly enhanced probabilities for above normal precipitation in Suriname, much of Guyana, and a sizeable additional portion of northern Brazil.

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

Slightly enhanced probabilities for near normal precipitation (25%-40%-35%) are forecast for eastern Venezuela, northern Guyana and adjacent extreme northern Brazil.

Slightly enhanced probabilities for above normal precipitation (25%-35%-40%)are forecast for the Galapagos Islands.

Slightly enhanced probabilities for below normal precipitation (40%-30%-30%)are forecast for a noteworthy portion of southern Brazil.

Slightly enhanced probabilities for below normal precipitation (40%-35%-25%) are forecast for western northeastern Brazil, east of the mouth of the Amazon.

Slightly enhanced probabilities for below normal precipitation (40%-35%-25%) are forecast for the Atlantic coast of central Argentina.

Slightly enhanced probabilities for below normal precipitation (40%-35%-25%) are forecast for south-central Chile and west-central Argentina.

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

An enhanced probability for above normal temperature (20%-35%-45%) is forecast for part of Southern Brazil, as well as a separate region stretching northwest-to-southeast across central Argentina. A third separate but associated center of such enhanced probability is found in southern interior Peru. Surrounding and connecting these three regions are broad areas of more weakly enhanced probabilities of above normal temperature, including Uruguay, much of the remainder of Argentina, most of Paraguay, northern and eastern Bolivia, additional portions of southern and western Brazil, much of interior Peru, and small parts of Ecuador and southern Colombia.

Slightly enhanced probabilities for near normal temperature (35%-40%-25%) are forecast for a portion of east-central Brazil.

Slightly enhanced probabilities for near normal temperature (25%-40%-35%) are forecast for central Colombia, most of Ecuador, southern Venezuela and part of northeastern Brazil.

Slightly enhanced probabilities for near normal temperature (25%-40%-35%) are forecast for the Galapagos Islands.

Slightly enhanced probabilities for near normal temperature (25%-40%-35%) are forecast for part of northern coatal Peru.

Slightly enhanced probabilities for near normal temperature (25%-40%-35%) are forecast for extreme southern Peru, extreme northern Cile, and western Bolivia.

November-December 2001-January 2002:

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

An enhanced probability for above normal precipitation (25%-30%-45%) is forecast for a portion of northern Brazil and adjacent extreme southern French Guiana, surrounded by more weakly enhanced probabilities for above normal precipitation in a sizeable portion of the remainder of northern Brazil, eastern Venezuela, and all of Guyana, Suriname and the remainder of French Guiana.

Slightly enhanced probabilities for near normal precipitation (35%-40%-25%) are forecast for northern Colombia and northern Venezuela.

Slightly enhanced probabilities for near normal precipitation (25%-40%-35%) are forecast for part of southeastern Venezuela and a small portion of northwestern Brazil.

Slightly enhanced probabilities for above normal precipitation (25%-35%-40%)are forecast for the Galapagos Islands.

Slightly enhanced probabilities for above normal precipitation (25%-35%-40%)are forecast for part of Northeast Brazil.

Slightly enhanced probabilities for below normal precipitation (40%-35%-25%) are forecast for a very small portion of the upper coast of northeastern Brazil.

Slightly enhanced probabilities for below normal precipitation (40%-35%-25%) are forecast for a portion of southeastern Bolivia, part of western Paraguay, much of Uruguay, extreme southwestern Brazil, central Chile, and parts of northern and central Argentina.

Slightly enhanced probabilities for below normal and near normal precipitation (40%-40%-20%)are forecast for extreme northern Venezuela.

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

Slightly enhanced probabilities for near normal temperature (35%-40%-25%) are forecast for part of the upper coast of southeastern Brazil.

Slightly enhanced probabilities for near normal temperature (25%-40%-35%) are forecast for much of Colombia, western Ecuador, northern interior Peru, and part of extreme western Brazil.

Slightly enhanced probabilities for near normal temperature (25%-40%-35%) are forecast for much of northeastern Brazil.

An enhanced probability for above normal temperature (20%-35%-45%) is forecast for the Pacific coasts of Ecuador and Peru, surrounded by more weakly enhanced probabilities for above normal temeprature in additional portions of both countries as well as the extreme southern coast of Colombia, and the Galapagos Islands.

Slightly enhanced probabilities for above normal temperature (25%-35%-40%)are forecast for south-central Chile and south-central Argentina.

December 2001-January-February 2002:

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

An enhanced probability for above normal precipitation (25%-30%-45%) is forecast for the Galapagos Islands.

Slightly enhanced probabilities for near normal precipitation (30%-40%-30% and 25%-40%-35%) are forecast for northeastern Brazil

Slightly enhanced probabilities for near normal precipitation (35%-40%-25%) are forecast for major portions of Venezuela and Colombia, as well as northern Guyana and a portion of northwestern Brazil.

Slightly enhanced probabilities for above normal precipitation (30%-30%-40%)are forecast for the southern coast of Ecuador and the northern coast of Peru.

Slightly enhanced probabilities for above normal precipitation (25%-35%-40%)are forecast for eastern interior Brazil.

Slightly enhanced probabilities for below normal precipitation (40%-35%-25%) are forecast for Southern Brazil, northern Argentina, southern Paraguay and much of Uruguay.

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

A greatly enhanced probability for above normal temperature (15%-35%-50%)is forecast for coastal Ecuador, northern Peru and the Galapagos Islands, surrounded by more weakly enhanced probabilities for above normal temperature in the remainder of Ecuador, part of the remainder of Peru, and southwestern Colombia.

Slightly enhanced probabilities for near normal temperature (30%-40%-30%)are forecast for northeastern Brazil.

Slightly enhanced probabilities for near normal temperature (25%-40%-35%) are forecast for a massive portion of central and northwestern South America, including most of the western half of Brazil, and parts of Bolivia, northern Chile, Peru, Columbia, Venezuela and Guyana.

Slightly enhanced probabilities for above normal temperature (25%-35%-40%)are forecast for eastern Colombia, extreme southern Venezuela and part of northwestern Brazil.

Slightly enhanced probabilities for above normal temperature (25%-35%-40), and near normal and above normal temperature (20%-40%-40%)are forecast for parts of southern Brazil.

Slightly enhanced probabilities for above normal temperature (25%-35%-40%)are forecast for south-central Chile and southwest-central Argentina.

Slightly enhanced probabilities for near normal and above normal temperature (20%-40%-40%)are forecast for part of northern Brazil.

Slightly enhanced probabilities for below normal temperature (40%-35%-25%) are forecast for a portion of southeastern Brazil.

Slightly enhanced probabilities for below normal and near normal temperature (40%-40%-20%)are forecast for southern Chile and southern Argentina.

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

CLIMATOLOGICAL AVERAGE: Temperature Precipitation

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

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

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