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 the demise of slightly cool but near-average conditions during the first forecast season with the development of weak, slightly above-average temperatures during the second season.  The forecast for slightly above average conditions is consistent with most other numerical and statistical forecasts of central and eastern Pacific SSTs.

B) Forecasts of the tropical Atlantic and the Indian ocean using statistical models developed by the CPTEC and IRI, respectively.

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 Center for Ocean-Land-Atmosphere Studies; Goddard Space Flight Center .

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 April - September 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 (variation) 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 period 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: April - June 2001 and July - September 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). 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 region XII in April - June 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.

An additional precipitation map is provided for the first season indicating probabilities for extreme precipitation anomalies. (Sometimes this map may be blank, due to no expect ed extremes.) 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.

April - June 2001:

PRECIPITATION

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

Region VIII) slightly enhanced probabilities of above-normal precipitation over much of the Philippines, Cambodia, southern Vietnam, much of Thailand and southern Burma along the Thailand border;

Region IX) slightly enhanced probabilities of above-normal precipitation over New Guinea, Papua New Guinea and the Solomon Islands;

Region X) slightly enhanced probabilities of below-normal precipitation over a region in the equatorial western and central Pacific from approximately 160E to 155W;

Region XI) slightly enhanced probabilities of near-normal to below-normal precipitation over southern Sumatra and most of Java;

Region XII) slightly enhanced probabilities of below-normal precipitation over much Western Australia;

Region XIII) slightly enhanced probabilities of below-normal precipitation over New Zealand.

TEMPERATURE

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

Region XIII) slightly enhanced probabilities of below-normal temperatures over much of Cambodia, southern areas of Laos,  Vietnam, and Thailand;

Region XVI) greatly enhanced probabilities of above-normal temperatures over the central and southern Philippines, parts of eastern Borneo, Celebes, New Guinea and the Solomon Islands and areas southeastward to Tonga;  within this region is a smaller area covering the southern Philippines, northern New Guinea, Papua New Guinea and much of the Solomon Islands for which an enhanced risk of extreme above-normal seasonal temperatures is forecast;

Region XVII) slightly enhanced probabilities of below-normal temperatures over New Zealand.

July - September 2001:

PRECIPITATION

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

Region XII) slightly enhanced probabilities of above-normal precipitation over Cambodia, southern Laos, southern Thailand and northern Peninsular Malaysia;

Region XIII) slightly enhanced probabilities of below-normal precipitation over southern Sumatra and western Borneo;

Region XIV) slightly enhanced probabilities of near-normal to below-normal precipitation over much of eastern Malaysia and Indonesia, excluding Sumatra and southwestern Borneo;

Region XV)  slightly enhanced probabilities of near-normal to above-normal precipitation over the near equatorial western and central Pacfic from approximately 150E to 160W.

Region XVI) slightly enhanced probabilities of below-normal precipitation over central western coastal areas of Western Australia;

Region XVII) slightly enhanced probabilities of below-normal precipitation over central and western Queensland.

TEMPERATURE

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

Region VIII) slightly enhanced probabilities of below-normal temperatures over most of Java and northward to southernmost Borneo;

Region IX) slightly enhanced probabilities of above-normal temperatures from central Sumatra and Peninsular Malaysia, much of Borneo, New Guinea, the Solomon Islands as well as nearby islands;

Region X)  slightly enhanced probabilities of below-normal temperatures over southeastern Queensland and central, eastern New South Wales, and eastern Victoria.