Fairfax Media Network

Agriculture Weather


Southern Oscillation Index

  • location
  • Aus

The Southern Oscillation Index (SOI) is calculated from the monthly or seasonal fluctuations in the air pressure difference between Tahiti and Darwin.

A strongly and consistently positive SOI pattern (e.g. consistently above about +6 over a two month period) is related to a high probability of above the long-term average (median) rainfall for many areas of Australia, especially areas of eastern Australia (including northern Tasmania) - La Niņa.

Conversely, a 'deep' and consistently negative SOI pattern (less than about minus 6 over a two month period, with little change over that period) is related to a high probability of below median rainfall for many areas of Australia at certain times of the year - El Niņo.

However, it is important to remember that the pattern of relationship between SOI and rainfall (and temperature) can vary depending on the particular season and region. Additionally, the change in SOI over a specified period can be as important in understanding relationships between SOI and rainfall as is the absolute value in SOI.

Southern Oscillation Index

SOI

Nino3.4 Index

Nino3.4
Display Your Local Weather

Weather News

Eastern seaboard's soaking start to autumn

12:46 EDT

Parts of Australia's eastern seaboard could receive more than a month's worth of rain in the next week, raising the risk of flooding during the opening days of autumn.

Melbourne's summer warmer than average, hot weather to continue in autumn

12:43 EDT

Melbourne may have avoided a scorching 40-degree day this summer, but warm weather is going to continue into autumn, the Bureau of Meteorology says.

Biggest rain since last winter soaking NSW coast

15:26 EDT

Parts of the New South Wales coast are in for their biggest downpours since last winter, bringing a much needed drink to gardens and parks but also causing some flooding.