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 Niña.

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 Niño.

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

September heat records on the forecast

11:36 EST

Unprecedented September heat will affect southern Queensland and northern NSW on Wednesday and Thursday, causing some locations to break records for the second time in a week.

Come by Chance picnic races buoys spirits of farmers despite heat and dust and drought

11:22 EST

"I have come here when it's flooded and we can't get out, and I've come here when it's been that bloody dusty we can't see the races." The venue in question was the Come by Chance racecourse and campdraft grounds, on a black-soil floodplain in western New South Wales.

Dam levels across NSW continue to hold despite record dry winter

09:40 EST

Despite a record dry winter and extremely warm daytime temperatures in New South Wales over the last four months, the state's dams are still relatively full.