The IRI has prepared this experimental Climate Outlook for Australia for July 2001 - December 2001. 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, July-August-September 2001, while during the second season, October-November-December 2001, 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 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 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 much of Western Autralia in July - September 2001 (Map A), there is a 30% probability that the precipitation will be in the wettest third of the years, a 30% 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. 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.

July - September 2001:

PRECIPITATION

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

Slightly enhanced probabilities for above normal precipitation (30%-30%-40%) are forecast for southern Myanmar, southwestern Thailand, Cambodia, and southern Vietnam.

Slightly enhanced probabilities for near normal and above normal precipitation (20%-40%-40%) are forecast for the Andaman Islands, south of Myanmar.

A greatly enhanced probability for below normal precipitation (50%-30%-20%) is forecast for central Sumatra. Weaker probabilities for below normal precipitation (45%-35%-25% and 40%-35%-20%) surround this region, including the remainder of Sumatra, most of Borneo, southwestern Malaysia, and Java. There is an enhanced risk of extreme below normal seasonal precipitation in central and southeastern Sumatra.

A greatly enhanced probability for below normal precipitation (50%-30%-20%) is forecast for some of the islands in the central tropial Pacific Ocean, such as the western islands of Kiribati. There is an enhanced risk of extreme below normal seasonal precipitation in this same region in the central tropical Pacific.

An enhanced probability for above normal precipitation (25%-30%-45%) is forecast for Halmahera Island and the extreme eastern tip of the northern Celebes. Separate but associated regions having this forecast include Fiji,Vanuatu Island, and the southeastern part of the Solomon Islands. Weaker probabilities for above normal precipitation (30%-30%-40% and 25%-35%-40%) surround and connect these regions, including New Caledonia, part of the central Solomon Islands, most of Papua New Guinea, eastern Irian Jaya, Buru and Ceram Islands, the central and northern Celebes, and part of the Federated States of Micronesia.

Slightly enhanced probabilities for near normal precipitation (30%-40%-30%) are forecast for part of the Marshall Islands, Nauru Island, and part of the Federated States of Micronesia.

An enhanced probability for below normal precipitation (45%-30%-25%) is forecast for western New South Wales of Australia. Weaker probabilities for below normal precipitation (40%-35%-25%) surround this region in Australia, including central and western New South Wales, part of Queensland, part of South Australia, the southern part of Northern Territory, and part of Western Australia.

Slightly enhanced probabilities for below normal precipitation (40%-35%-25%) are forecast for southern New Zealand and Auckland Island.

TEMPERATURE

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

Slightly enhanced probabilities for near normal temperature (25%-40%-35%) are forecast for Hainan Island of China, southern Vietnam, eastern Cambodia, southern Myanmar, southern Thailand, most of Malaysia, Sumatra, and western Borneo. The region extends also to Java, where the probabilities change to 35%-40%-25%.

An enhanced probability for above normal temperature (25%-30%-45% and 20-35%-45%) is forecast for all of the Philippines except for the northernmost tip, Palau Island, and the northern portion of the Indonesian part of Malaysia. Weaker probabilities for above normal temperature (25%-35%-40%) surround this region, including the northernmost tip of the Philippines, a central portion of the Indonesian part of Malaysia, Brunei, and the northernmost arm of the Celebes.

A greatly enhanced probability for below normal temperature (50%-30%-20%) is forecast for Western Australia and part of the Northern Territory of Australia. Weaker probabilities for below normal temperature (45%-30%-25%, 40%-35%-25%, and 40%-30%-30%) surround that region, including the remainder of Western Australia, most of South Australia, part of Northern Territory, much of New South Wales, part of Queensland, and a small portion of the islands in central Indonesia.

A very greatly enhanced probability for above normal temperature (15%-25%-60%) is forecast for part of the Solomon Islands, Vanuatu Island, New Caledonia, the main island of Fiji, and Tonga. Weaker probabilities for above normal temperature (15%-35%-50%, 20%-35%-45%, and 25%-35%-40%) surround and connect those regions, including Wallis and Futuna Island, the remaining portions of the Solomon Islands, extreme southern and eastern Papua New Guinea, northernmost Queensland of Australia, Samoa, American Samoa, and Niue Island. There is an enhanced risk of extreme above normal seasonal temperatures in the Solomon Islands, New Caledonia, Fiji, and farther east, and a slightly enhanced risk in the immediately surrounding areas.

A greatly enhanced probability for above normal temperature (15%-35%-50%) is forecast for New Zealand and Auckland Island. Weaker probabilities for above normal temperature (25%-30%-45%) are found across the Tasman Sea in central and southern Tasmania.

Slightly enhanced probabilities for above normal temperature (25%-35%-40%) are forecast for parts of the Marshall Islands, and for some of the Federated States of Micronesia, and part of western Kiribati.

October - December 2001:

PRECIPITATION

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

Slightly enhanced probabilities for above normal precipitation (30%-30%-40%) are forecast for southern Myanmar, southern Thailand and northwestern Malaysia.

A greatly enhanced probability for above normal precipitation (20%-30%-50%) is forecast for central Indonesia, including Timor, the southernmost and northernmost Celebes, and some of the Moluccas Islands. Weaker probabilities for above normal precipitation (20%-35%-45% and 25%-35%-40%) surround this region, including the Philippines, Palau Island, Papua New Guinea, Irian Jaya, eastern Java, Vanuatu Island, New Caledonia, some of the Federated States of Micronesia, western Kiribati and Tuvalu Island.

A greatly enhanced probability for below normal precipitation (50%-30%-20%) is forecast for southeastern Sumatra and western Java. Weaker probabilities for below normal precipitation (40%-35%-20%) surround this region, including south-central Sumatra, central Java and extreme southwestern Borneo.

Slightly enhanced probabilities for below normal precipitation (40%-30%-30%) are forecast for part of Western Australia, much of South Australia, and the southern part of Victoria, Australia.

Slightly enhanced probabilities for near normal precipitation (30%-40%-30%) are forecast for the vicinity of Wallis and Futuna Islands, Samoa and American Samoa.

TEMPERATURE

An enhanced probability for above normal temperature (20%-35%-45%) is forecast for Guam and vicinity, the Marshall Islands, and Wake Island. Weaker probabilities for above normal temperature (25%-35%-40%) surround this region, including the Solomon Islands, the westernmost Federated States of Micronesia, extreme southeastern Papua New Guinea, Palau Island, the southern and central Philippines, the Cape York Peninsula of Queensland, Australia, and the western part of Kiribati in which near normal shares an enhanced likelihood (20%-40%-40%).

Slightly enhanced probabilities for below normal temperature (40%-30%-30%) are forecast for the southwestern portion of Western Australia.

Slightly enhanced probabilities for above normal temperature (25%-35%-40%) are forecast for part of South Australia, much of Victoria and southwestern New South Wales, Australia.

Slightly enhanced probabilities for near normal and above normal temperature (20%-40%-40%) are forecast for the southern three-quarters of New Zealand, and for Auckland Island.

Slightly enhanced probabilities for near normal temperature (25%-40%-35%) are forecast for the northern one-quarter of New Zealand.

OBSERVED CLIMATOLOGY DATA for Jul-Aug-Sep and Oct-Nov-Dec-Mar

CLIMATOLOGICAL AVERAGE: Temperature Precipitation

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

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

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