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

Farmers rejoice as deluge fills rain gauges in Perth, Wheatbelt

13:15 EST

A low pressure system which has drenched Perth, the South West and parts of the Wheatbelt has farmers rejoicing.

Western Australia caught in heavy rain and thunderstorms

12:44 EST

Powerful thunderstorms have been drenching southwestern Australia, with some locations recording their wettest day in over a decade.

Cold snap could see snow fall as low as sea level in Hobart on Monday

08:39 EST

Weather forecasters are predicting snow across Tasmania over the weekend and possible snow in Hobart for the first time since 1986.