Seasonal Climate Outlook Message for December 1999 to March 2000

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SOI message 15th December 1999

The average SOI over the previous 30 days has risen to +16.3 . Based on the SOI, the probabilities of exceeding median rainfall during the total period from December to February range predominantly between 50% and 70% in most of the eastern States, rising to 80% in some near-coastal areas of Queensland and NSW.

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Review of Climatic Forecasts and Information

Based on the latest values and trends of the SOI, the probabilities of exceeding median rainfall during the total December-February period are 50% or greater over most of the eastern States of Australia. However, along the Queensland coast (up to 400 kms inland), coastal NSW, and much of inland NSW they are mainly 60-80%. Overall this represents a reasonable outlook for summer rainfall.

The continuing 'cool' sea-surface temperature (SST) anomalies in the eastern equatorial Pacific Ocean combined with increasingly 'warm' SST anomalies around northern Australia suggest a continuing 'weak' La Nina pattern. In very general terms, this type of pattern suggests higher rainfall than normal for many districts in northern and eastern Australia this summer. Most experimental models are suggesting that neutral conditions will predominate by about April. A recent forecast from the Bureau of Meteorology indicates that for much of New South Wales, south-east Queensland and Western Australia, there is a 60% to 75% chance that rainfall will exceed the median during the total December-February period. This outlook is based on sea-surface temperature patterns; currently probabilities are boosted by temperatures in the Indian Ocean off Western Australia being warmer than normal.

Combining the rainfall outlook with current soil water and pasture condition, the probabilities of above-median pasture growth during the total December-February period are 70-100% over Queensland except for the far central west.

The behaviour of the 30- to 50-Day Oscillation has been reassessed, and it appears that it is currently passing through northern Australia. The next passage of it is expected in the third week of January.

It is important to obtain more detailed information for your location. This can be obtained from the Australian Rainman software package. Also a lot of additional information is available on our FarmFax system, our Internet World Wide Web service called 'The Long Paddock', and on BoM's Fax and internet information services.

Last updated: 14 December 1999