SOI MESSAGE - 27 October 1999
The average SOI over the previous 30 days has risen to +9.6. 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 October to December period are mainly around 50% in the eastern half of Australia.
Sea-surface temperatures in the Pacific Ocean indicate a very weak La Nina pattern which is close to a neutral one. Converse to last month, most experimental models are now suggesting that neutral conditions will predominate in six months time. Temperatures are now mainly normal in waters off Queensland and the Northern Territory.
Sea -surface temperatures in the Indian Ocean off Western Australia are warmer than normal. The Bureau of Meteorology is suggesting that this indicates reasonably high probabilities of above-median rainfall in eastern Australia during the total November-January period.
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 this week or early next week. 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. We recommend combined use of the Australian RAINMAN package and the Bureau of Meteorology's Seasonal Climate Outlook. 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.