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

Fresh dusting of snow to the southeast

17:23 EST

A cold front has brought snow to the Alps of New South Wales, priming a good weekend to hit the snow fields.

Young and in drought: why farmers and young entrepreneurs stay on in regional and remote Australia

14:07 EST

There's rarely a time when the world's driest continent is not faced with a drought.

Australian Ski resorts going under cover

13:02 EST

Australia's ski resorts are finally becoming covered by fresh, natural snow, a result of the first decent cold blast in a few weeks.