SOI Message - 17 November 1999
The average SOI over the previous 30 days is +7.6. Based on the SOI, the probabilities of exceeding median rainfall during the total November to January period are quite variable, but remain around 50% in much of the eastern States.
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 November-January period are quite variable over the eastern half of Australia. They are around 50% over much of this area. The exceptions are parts of central-western Qld, south-western Victoria and Tasmania where probabilities are 60-80%; and near the Qld-NSW border, and in coastal areas and the north-eastern quarter of NSW where they are 10-40%.
Sea-surface temperatures in the Pacific Ocean indicate a weak La Nina pattern. However, the Bureau of Meteorology Research Centre (BMRC) says temperatures in waters off the Australian coastline have increased considerably during Aug-Oct; they are now mostly above average except in Queensland where they are mainly normal. Most experimental models are suggesting that neutral conditions will predominate by about April. The most recent forecast from the Bureau of Meteorology, released on 11November, 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.
The likelihood of above-median pasture growth in October to December (during a 'neutral' SOI year) varies little from the 'all years' average values. Providing rainfall is at least average over that period, prospects for above-average pasture growth are high in areas where pasture condition is good (i.e. high perennial grass basal cover).
The next passage of the 30- to 50-Day Oscillation is expected in the fourth week of November. For the past few months it has been a very weak phenomenon, only identifiable after it has passed.
It is important to obtain more detailed information for your location. This can be found via 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.