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

SA weather: Power 'gradually' returning after blackout plunged state into darkness

22:02 EST

Power is gradually being turned back on across parts of South Australia but much of the state remains in darkness after a widespread blackout.

Tasmania braces for weather system that battered South Australia

21:18 EST

Tasmanians are being warned to prepare for wind and rains forecast to lash the state on Thursday.

SA weather: State-wide power loss raises 'serious questions', Josh Frydenberg says

21:01 EST

Federal Energy Minister Josh Frydenberg says serious questions will be raised about how the entirety of South Australia could be left without electricity in the wake of a huge storm, dubbed the largest in 50 years.