The IRI has prepared this experimental Climate Outlook for South America for October 2001 - March 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, October-December 2001, November-January 2002, December-February 2002, while during the second season, January-March 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.

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 October 2001 - March 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: October-December 2001, November-January 2002, December-February 2002 and January-March 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 5cm of precipitation typically occurs over the season. Otherwise, for example, in the case of October-December 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 southeastern 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.

An additional precipitation map is provided for the first season indicating probabilities for extreme precipitation anomalies. Extremes are defined as anomalies that fall within the top and bottom 15th percentile of the observed records. A priori, there is a 15% probability of being within the extremely wet category, and a 15% probability of being within the extremely dry category, leaving a 70% probability that the precipitation will not be extreme. The maps indicate areas of increased risk of extreme precipitation totals. Three levels of increased risk are defined: slightly enhanced risk, enhanced risk, and greatly enhanced risk. For slightly enhanced risk, there is a 25-40% probability that precipitation will be within the indicated extreme, i.e. wet or dry. This represents an approximate doubling of the climatological risk. For enhanced risk, there is a 40-50% probability that precipitation will be within the indicated extreme. This represents an approximate tripling of the climatological risk. For greatly enhanced risk, the probability that precipitation will be within the indicated extreme exceeds 50%, i.e. the indicated extreme is the most likely outcome. A similar map is provided in the first season indicating probabilities of extreme temperature anomalies.

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

October-November-December 2001:

Slightly enhanced probabilities for above normal precipitation (25%-35%-40%) are forecast for the easternmost tip of northeast Brazil.

An enhanced probability for above normal precipitation (25%-30%-45%) is forecast for northern Chile, surrounded by more weakly enhanced probabilities for above normal precipitation in additional areas in northern Chile, southern Peru northern Argentina and southern Bolivia.

Slightly enhanced probabilities for near normal precipitation (35%-40%-25%) are forecast for Guyana, Suriname, French Guiana, southeastern Venezuela and part of northern Brazil.

Slightly enhanced probabilities for near normal precipitation (30%-40%-30%) are forecast for the Galapagos Islands as well as the coast of Ecuador.

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

Slightly enhanced probabilities for near normal precipitation (30%-40%-30%) are forecast for central Argentina.

An enhanced probability for below normal precipitation (45%-30%-25%) is forecast for N Colombia, northern Colombia and northern Venezuela, surrounded by more weakly enhanced probabilities for below normal precipitation in additional portions of Colombia and Venezuela.

A greatly enhanced probability for below normal precipitation (55%-25%-20%) is forecast for part of northern Brazil near and east of the mouth of the Amazon, surrounded by more weakly enhanced probabilities for below normal precipitation in additional portions of northern and northeastern Brazil.

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

An enhanced probability for below normal precipitation (45%-35%-20%) is forecast for part of south-central Chile, surrounded by more weakly enhanced probabilities for below normal precipitation in additional portions of central and southern Chile and west-central Argentina.

Slightly enhanced probabilities for below normal precipitation (40%-30%-30%) are forecast for extreme southern Argentina and Chile, including Drake Passage.

An enhanced probability for above normal temperature (20%-35%-45%) is forecast for part of northern Brazil, surrounded by more weakly enhanced probabilities for above normal temperature in a significant portion of northern South America stretching from Peru through Venezuela to central Brazil and northern Bolivia.

An enhanced probability for above normal temperature (20%-35%-45%) is forecast for part of southern Brazil and southern Paraguay, surrounded by more weakly enhanced probabilities for above normal temperature in additional portions of mainly southern Brazil, Uruguay, Paraguay, eastern Bolivia and northern Argentina.

An enhanced probability for above normal temperature (20%-35%-45% and 25%-30%-45%) is forecast for central Chile and central Argentina, surrounded by more weakly enhanced probabilities for above normal temperature in additional portions of Chile and Argentina, Uruguay and parts of Bolivia and southern Brazil.

A very greatly enhanced probability for above normal temperature (15%-25%-60%) is forecast for Easter Island.

Slightly enhanced probabilities for near normal temperature (25%-40%-35%) are forecast for southwestern Venezuela and eastern Colombia.

Slightly enhanced probabilities for near normal temperature (25%-40%-35%) are forecast for much of Brazil, French Guiana, and Suriname.

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

Slightly enhanced probabilities for near normal temperature (35%-40%-25%) are forecast for extreme southern Argentina and the Falkland Islands.

Slightly enhanced probabilities for below normal and near normal temperature (40%-40%-20%) are forecast for the Galapagos Islands.

November-December-January 2001-2002:

Slightly enhanced probabilities for above normal precipitation (30%-30%-40%) are forecast for the leeward and windward islands of the Lesser Antilles.

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

Slightly enhanced probabilities for near normal and above normal precipitation (20%-40%-40%) are forecast for the Galapagos Islands.

An enhanced probability for above normal precipitation (20%-35%-45%) is forecast for the eastern tip of northeast Brazil, surrounded by more weakly enhanced probabilities for above normal precipitation in additional portions of eastern and central Brazil.

Slightly enhanced probabilities for near normal and above normal precipitation (20%-40%-40%) are forecast for northern and central Chile, extreme southern Peru, extreme northern Argentina and southern Bolivia.

Slightly enhanced probabilities for near normal precipitation (30%-40%-30%) are forecast for western Colombia and extreme northern Venezuela.

Slightly enhanced probabilities for near normal precipitation (25%-40%-35%) are forecast for Guyana, Suriname, French Guiana and part of northern Brazil.

Slightly enhanced probabilities for near normal precipitation (35%-40%-25%) are forecast for much of Paraguay, a small part of southern Brazil, and part of northern Argentina.

Slightly enhanced probabilities for below normal precipitation (40%-30%-30%) are forecast for central Venezuela.

Slightly enhanced probabilities for below normal precipitation (40%-30%-30%) are forecast for the coast of Ecuador.

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

Slightly enhanced probabilities for below normal precipitation (40%-30%-30%) are forecast for a small portion of the coastal region of southeastern Brazil.

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

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

Slightly enhanced probabilities for above normal temperature (25%-35%-40%) are forecast for a small portion of western Brazil and extreme northern Bolivia.

A greatly enhanced probability for above normal temperature (15%-30%-55%) is forecast for a portion of southern Brazil, surrounded by more weakly enhanced probabilities for above normal temperature in additional portions of southern Brazil, Paraguay, central and eastern Bolivia, and northern Argentina.

A greatly enhanced probability for above normal temperature (20%-30%-50%) is forecast for a portion of south-central Argentina, surrounded by more weakly enhanced probabilities for above normal temperature in additional portions of Argentina, Uruguay, and part of Chile.

Slightly enhanced probabilities for near normal temperature (25%-40%-35% and 35%-40%-25%) are forecast for much of the northern and central portions of South America, including the Galapagos Islands.

Slightly enhanced probabilities for near normal temperature (25%-40%-35%) are forecast for parts of southern Chile and southern Argentina.

December-January-February 2001-2002:

Slightly enhanced probabilities for above normal precipitation (25%-35%-40%) are forecast for southeastern Colombia, extreme southern Venezuela, extreme northwestern Brazil and extreme northeastern Peru.

An enhanced probability for above normal precipitation (25%-30%-45%) is forecast for part of the northern coast of Peru, surrounded by more weakly enhanced probabilities for above normal precipitation in a slightly enlarged area of northwestern Peru and extreme southwestern Ecuador.

Slightly enhanced probabilities for above normal precipitation (30%-30%-40%) are forecast for a small portion of west-central Brazil.

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

Slightly enhanced probabilities for above normal precipitation (25%-35%-40%) are forecast for the easternmost portion of northeast Brazil, and slightly to its south.

Slightly enhanced probabilities for above normal precipitation (30%-30%-40%) are forecast for part of southern and upper southeastern Brazil.

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

Slightly enhanced probabilities for near normal precipitation (30%-40%-30%) are forecast for most of Guyana, Suriname, French Guiana and a small portion of northern Brazil.

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

Slightly enhanced probabilities for near normal precipitation (35%-40%-25%) are forecast for northeastern Brazil and the immediate surroundings.

Slightly enhanced probabilities for near normal precipitation (25%-40%-35%) are forecast for a tiny region in north-central Brazil.

Slightly enhanced probabilities for below normal and near normal precipitation (40%-40%-20%) are forecast for northern Brazil near the mouth of the Amazon.

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

An enhanced probability for above normal temperature (20%-35%-45%) is forecast for the northern coast of Peru and the extreme southern coast of Ecuador, flanked to the north by more weakly enhanced probabilities for above normal temperature in the central coast of Ecuador.

An enhanced probability for above normal temperature (25%-30%-45%) is forecast for parts of southern and central Chile and much of southern Argentina, surrounded by more weakly enhanced probabilities for above normal temperature in significant additional portions of Chile and Argentina, as well as extreme western Uruguay.

Slightly enhanced probabilities for near normal temperature (35%-40%-25% and 25%-40%-35%) are forecast for nearly all of the northern two-thirds of South America, with the exception of the warm-forecasted regions in coastal Peru and Ecuador mentioned above.

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 Easter Island.

Slightly enhanced probabilities for near normal temperature (25%-40%-35%) are forecast for extreme southern Brazil and southern Uruguay.

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

January-February-March  2001-2002:

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

An enhanced probability for above normal precipitation (20%-35%-45%) is forecast for the eastern tip of northeast Brazil, surrounded by more weakly enhanced probabilities for above normal precipitation in additional portions of the same vicinity.

Slightly enhanced probabilities for above normal precipitation (25%-35%-40%) are forecast for central and western Brazil, and the extreme northern tip of adjacent Bolivia.

Slightly enhanced probabilities for near normal precipitation (35%-40%-25% and 25%-40%-35%) are forecast for parts of Venezuela, Suriname, French Guiana, and north-central and northern Brazil.

Slightly enhanced probabilities for near normal precipitation (25%-40%-35%) are forecast for northeastern Brazil, extending into the interior as well as westward toward the mouth of the Amazon.

Slightly enhanced probabilities for below normal and near normal precipitation (40%-40%-20%) are forecast for, western Colombia.

Slightly enhanced probabilities for below normal and near normal precipitation (40%-40%-20%) are forecast for eastern Venezuela and most of Guyana and Suriname.

An enhanced probability for above normal temperature (20%-35%-45%) is forecast for the coasts of Ecuador and northern Peru.

Slightly enhanced probabilities for above normal temperature (25%-35%-40%) are forecast for northwestern Peru, southern Colombia and western Brazil.

Slightly enhanced probabilities for above normal temperature (25%-35%-40%) are forecast for southern Brazil, extreme northeastern Argentina, extreme northern Uruguay and southern Paraguay.

Slightly enhanced probabilities for above normal temperature (25%-35%-40%) are forecast for a small part of north-central Argentina.

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

Slightly enhanced probabilities for near normal temperature (35%-40%-25% and 25%-40%-35%) are forecast for most of the northern two-thirds ofSouth America, including the Galapagos Islands, plus Uruguay, part of central Argentina and part of the upper Atlantic coast of Argentina.

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

Slightly enhanced probabilities for near normal temperature (25%-40%-35%) are forecast for part of southern Argentina and most of southern Chile.

Slightly enhanced probabilities for below normal and near normal temperature (40%-40%-20%) are forecast for the easternmost sector of northeastern Brazil, and the coastal region immediately to its south.

Slightly enhanced probabilities for below normal and near normal temperature (40%-40%-20%) are forecast for a small portion of south-central Brazil.

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

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