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 CPC ; 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 July - December 2001 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 two seasons: July - September 2001 and October - December 2001. 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 southern Mexico 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 much of the state of California in the U.S.

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 above normal precipitation (25%-35%-40%)are forecast for southern Alaska and the adjacent western Canadian coast.

Slightly enhanced probabilities for below normal precipitation (40%-35%-25%) are forecast for extreme northern Canada.

Slightly enhanced probabilities for below normal precipitation (40%-35%-25%) are forecast for the northwest coast of the United States.

Slightly enhanced probabilities for below normal precipitation (40%-35%-25%) are forecast for southern Mexico and portions of some neighboring Latin American nations.

Slightly enhanced probabilities for below normal precipitation (40%-35%-25%) are forecast for the southernmost portion of Hawaiian Islands of the U.S.

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 southwestern Mexico, surrounded by more weakly enhanced probabilities for above normal temperature in northern Guatemala, most of the remainder of Mexico, and a sizeable portion of the western United States.

A greatly enhanced probability for above normal temperature (20%-30%-50%)is forecast for Haiti, the Dominican Republic and Puerto Rico, surrounded by more weakly enhanced probabilities for above normal temperature in most of the remainder of the West Indies of the Caribbean.

An enhanced probability for above normal temperature (15%-40%-45%) is forecast for extreme eastern Canada, surrounded by more weakly enhanced probabiities for above normal temperature in additional portions of eastern Canada and the northeastern United States.

Slightly enhanced probabilities for near normal temperature (30%-40%-30%)are forecast for the Aleutian Islands of Alaska, United States.

Slightly enhanced probabilities for near normal temperature (30%-40%-30%)are forecast for the Hawaiian islands of the U.S.

Slightly enhanced probabilities for near normal temperature (25%-40%-35%) are forecast for the southern part of Latin America.

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

Slightly enhanced probabilities for above normal temperature (25%-35%-40%)are forecast for a small portion of northeastern Canada.

Slightly enhanced probabilities for below normal temperature (40%-30%-30%)are forecast for northern Alaska and a small portion adjacent northwestern Canada.

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

October-November-December 2001:

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

Slightly enhanced probabilities for near normal precipitation (35%-40%-25%) are forecast for a portion of southern Latin America.

Slightly enhanced probabilities for near normal precipitation (25%-40%-35%) are forecast for part of northwestern Mexico, including Baja California.

Slightly enhanced probabilities for above normal precipitation (30%-30%-40%)are forecast for northwestern Alaska, U.S.

Slightly enhanced probabilities for above normal precipitation (30%-30%-40%)are forecast for southern Alaska, U.S.

Slightly enhanced probabilities for above normal precipitation (25%-35%-40%)are forecast for a small part of northwestern Mexico.

Slightly enhanced probabilities for below normal precipitation (40%-35%-25%) are forecast for southeastern Florida of the United States, and the Bahamas.

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 a small portion of the west coast of Mexico, surrounded by more weakly enhanced probabilities for above normal temperature in most of the remainder of Mexico, all except the southernmost nations of Latin America, and much of the West Indies in the Caribbean region.

An enhanced probability for below normal temperature (45%-35%-20%)is forecast for part of northeastern Canada, surrounded by more weakly enhanced probabilities for below normal temperature in a major portion of the remainder of eastern Canada.

Slightly enhanced probabilities for near normal temperature (25%-40%-35%) are forecast for a small portion of the state of Texas in the southern United States.

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

Slightly enhanced probabilities for near normal temperature (25%-40%-35%) are forecast for the northern portion of the Lesser Antilles in the Caribbean region.

Slightly enhanced probabilities for near normal temperature (25%-40%-35%) are forecast for the southern nations of Latin America.

Slightly enhanced probabilities for above normal temperature (30%-30%-40%)are forecast for extreme western Alaska, U.S.

Slightly enhanced probabilities for above normal temperature (30%-30%-40%)are forecast for significant portions of the central and western United States.

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

November-December 2001-January 2002:

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

Slightly enhanced probabilities for above normal precipitation (25%-35%-40%)are forecast for the south-central United States and adjacent northern Mexico.

Slightly enhanced probabilities for below normal precipitation (40%-30%-30%)are forecast for a small portion of the eastern United States, centered on the state of Ohio, and a small part of adjacent southern Ontario, Canada.

Slightly enhanced probabilities for below normal precipitation (40%-30%-30%)are forecast for the Yucatan Penninsula, Mexico, and the northrn parts of Belize and Guatemala.

Slightly enhanced probabilities for below normal precipitation (40%-30%-30%)are forecast for eastern Honduras, and part or all of Nicaragua, Costa Rica, Costa Rica and Panama.

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

An enhanced probability for above normal temperature (20%-35%-45%) is forecast for the Aleutian Islands of Alaska, surrounded by more weakly enhanced probabilities for above normal temperature in the more outer Aleutian Islands and in most of the southern half of Alaska.

An enhanced probability for above normal temperature (20%-35%-45%) is forecast for a small part of the northern Rocky Mountains of the U.S. (centered on the state of Wyoming), surrounded by by more weakly enhanced probabilities for above normal temperature in a larger portion of the northwestern United States.

An enhanced probability for above normal temperature (20%-35%-45%) is forecast for southern Mexico, Guatemala Belize, Jamiaca and part of Haiti and Dominican Republic, surrounded by more weakly enhanced probabilities for above normal temperature in central Mexico, Cuba, Puerto Rico, southern Bahamas and several of the Latin American nations.

An enhanced probability for below normal temperature (45%-35%-20%)is forecast for the extreme northeastern United States and eastern Canada, surrounded by more weakly enhanced probabilities for below normal temperature in more of the eastern and northern United States as well as southeastern and south-central Canada.

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

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

Slightly enhanced probabilities for above normal temperature (25%-35%-40%)are forecast for extreme northwesterern Canada and adjacent northeastern Alaska.

Slightly enhanced probabilities for above normal temperature (25%-35%-40% and 30%-30%-40%)are forecast for north-central Canada, centered near the western shore of Hudson Bay.

Slightly enhanced probabilities for above normal temperature (25%-35%-40%)are forecast for extreme northeastern Canada and northwestern Greenland.

December 2001-January-February 2002:

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

Slightly enhanced probabilities for near normal precipitation (30%-40%-30%)are forecast for the northern Bahamas and northern Cuba.

Slightly enhanced probabilities for near normal precipitation (30%-40%-30%)are forecast for a small portion of southern Mexico and northwestern Guatemala.

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

Slightly enhanced probabilities for near normal precipitation (25%-40%-35%) are forecast for a small portion of central Mexico.

Slightly enhanced probabilities for above normal precipitation (30%-30%-40%)are forecast for part of northwestern Canada and part of the southern coast of Alaska.

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

Slightly enhanced probabilities for above normal precipitation (25%-35%-40%)are forecast for part of the southwestern United States and adjacent northwestern Mexico.

Slightly enhanced probabilities for above normal precipitation (25%-35%-40%)are forecast for the southern United States along the coast of the Gulf of Mexico, and a small portion of adjacent northern Mexico.

Slightly enhanced probabilities for below normal precipitation (40%-30%-30%)are forecast for northern Canada, near Hudson Bay.

Slightly enhanced probabilities for below normal precipitation (40%-35%-25%) are forecast for a portion of the northwestern United States.

Slightly enhanced probabilities for below normal precipitation (40%-35%-25%) are forecast for part of the northern United States near the Great Lakes, and a small part of adjacent southern Canada.

Slightly enhanced probabilities for below normal precipitation (40%-35%-25%) are forecast for the southern Latin American nations, from Nicaragua southward to Panama.

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

An enhanced probability for above normal temperature (20%-35%-45%) is forecast for the Hawaiian Islands, U.S.

An enhanced probability for above normal temperature (20%-35%-45%) is forecast for Haiti and Jamaica, surrounded by more weakly enhanced probabilities for above normal temperature in the Dominican Republic, eastern Cuba and the southern Bahamas.

Slightly enhanced probabilities for near normal temperature (35%-40%-25%) are forecast for eastern Newfoundland, Canada.

Slightly enhanced probabilities for near normal temperature (25%-40%-35%) are forecast for part of the Caribbean region, including the northern Bahamas, western Cuba, Puerto Rico, the Yucatan Penninsula of Mexico, and portions of several Latin American nations.

Slightly enhanced probabilities for above normal temperature (30%-30%-40%)are forecast for northwestern Greenland, as well as part of Baffin Bay.

Slightly enhanced probabilities for above normal temperature (30%-30%-40%)are forecast for part of northern Alaska.

Slightly enhanced probabilities for above normal temperature (30%-30%-40%)are forecast for northwestern central Canada.

Slightly enhanced probabilities for above normal temperature (25%-35%-40%)are forecast for a portion of southern Mexico, and part or all of Guatemala, Belize, El Salvador, Honduras, and Nicaragua.

Slightly enhanced probabilities for below normal temperature (40%-30%-30%)are forecast for a portion of the Canadian Maritime provinces.

Slightly enhanced probabilities for below normal temperature (40%-35%-25%) are forecast for a substantial portion of the eastern and northeastern United States.

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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