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

Dust storm takes outback Queensland town by surprise, damages homes

18:23 EDT

Charleville has been transformed into an apocalyptic sea of orange, as a dust storm whips through the south-western Queensland town.

Severe storms strike Queensland

16:50 EDT

It has been a cool and wet day in central Queensland as severe storms affect parts of the state.

Broome smashes annual rainfall record in less than two months as Cyclone Kelvin caps big wet

16:46 EDT

Broome has officially endured its wettest year on record after more than two years' worth of rain fell on the Kimberley in the past two months.