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 northwestern Iran 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 southern Italy, among other countries.

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:

Slightly enhanced probabilities for below normal precipitation (40%-35%-25%) are forecast for northwestern Iran and Armenia.

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

A greatly enhanced probability for above normal temperature (20%-30%-50%)is forecast for the Atlantic Ocean near the grid point with coordinates 54N, 20W.

An enhanced probability for above normal temperature (20%-35%-45%) is forecast for part of Scotland, Ireland and Northern Ireland, surrounded by more weakly enhanced probabilities for above normal temperature in the remainder of the United Kingdom, and in northwestern France.

Slightly enhanced probabilities for near normal temperature (25%-40%-35%) are forecast for the central west coast of France.

Slightly enhanced probabilities for near normal temperature (25%-40%-35%) are forecast for southern Portugal and southern Spain.

Slightly enhanced probabilities for above normal temperature (30%-30%-40% and 25%-35%-40%)are forecast for southwestern Russia, eastern Turkey, northern Iran, much of Syria and most of Iraq.

Slightly enhanced probabilities for above normal temperature (25%-35%-40%)are forecast for southern Iceland.

Slightly enhanced probabilities for above normal temperature (25%-35%-40%)are forecast for the Azores and vicinity, in the Atlantic Ocean.

Slightly enhanced probabilities for above normal temperature (25%-35%-40%)are forecast for southeastern Spain.

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

October-November-December 2001:

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

Slightly enhanced probabilities for below normal precipitation (40%-30%-30%)are forecast for Ireland and Northern Ireland.

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

Slightly enhanced probabilities for near normal temperature (25%-40%-35%) are forecast for part of the west coast of France, all of Portugal, western Spain, and the Balearic Islands and surrounding portion of the Mediterranean Sea.

Slightly enhanced probabilities for above normal temperature (30%-30%-40%)are forecast for southwest Russia, eastern Turkey, and small portions of northwestern Iran, Syria, and Iraq.

Slightly enhanced probabilities for above normal temperature (25%-35%-40%)are forecast for much of eastern Spain.

November-December 2001-January 2002:

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

(No regions for enhanced probabilities in Europe.)

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

Slightly enhanced probabilities for near normal temperature (30%-40%-30%)are forecast for southern Sardinia, of Italy.

Slightly enhanced probabilities for near normal temperature (25%-40%-35%) are forecast for part of Scotland and Shetland Islands.

Slightly enhanced probabilities for near normal temperature (25%-40%-35%) are forecast for much of southern Norway, southwestern Sweden, and northern Denmark.

Slightly enhanced probabilities for above normal temperature (30%-30%-40%)are forecast for southern France and extreme northeastern Spain.

Slightly enhanced probabilities for above normal temperature (25%-35%-40%)are forecast for extremem western Wales, part of western Scotland, much of Ireland, and Northern Ireland.

Slightly enhanced probabilities for above normal temperature (25%-35%-40%)are forecast for northern Germany, extreme northwestern Poland and extreme southern Sweden.

Slightly enhanced probabilities for above normal temperature (25%-35%-40%)are forecast for part of southwestern Russia, much of Turkey, Syria, Iraq, western Iran and other countries in the Middle East.

Slightly enhanced probabilities for below normal temperature (40%-30%-30%)are forecast for Spitsbergen and vicinity in the Arctic Ocean.

December 2001-January-February 2002:

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

(No regions for enhanced probabilities in Europe.)

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

Slightly enhanced probabilities for near normal temperature (25%-40%-35%) are forecast for much of southern and central Sweden, southern Norway, Denmark, and northern extremes of Germany and Poland.

Slightly enhanced probabilities for above normal temperature (25%-35%-40%)are forecast for eastern Iceland.

Slightly enhanced probabilities for above normal temperature (30%-30%-40%)are forecast for Franz Josef Land, to the north of Novaya Zemlya in the Barents Sea in the Arctic Ocean.

Slightly enhanced probabilities for below normal temperature (40%-30%-30%)are forecast for Spitsbergen and vicinity in the Arctic Ocean.

Slightly enhanced probabilities for below normal temperature (40%-35%-25%) are forecast for extreme southwestern Turkcy and the island of Crete, of Greece.

OBSERVED CLIMATOLOGY DATA 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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