Southern Oscillation Index
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.
Now Temperature
At Darwin Ap
08:10 CST
27°C
34°C
Mostly sunny
Weather News
BOM warns cyclone expected to form from tropical low over Gulf of Carpentaria
09:03 EDT
There is a high chance a tropical low that has been threatening for days to intensify into a cyclone in the Gulf of Carpentaria will finally do so today, the Bureau of Meteorology has said.
NSW emergency service cranks up campaign to stop people driving into floodwater
08:44 EDT
Emergency services are frustrated by people making bad decisions when faced with floodwater, as recent studies on flood deaths show young men and children are the most at-risk of dying.
NSW weather: Storm hits Hunter and Central Coast, BOM predicts heavy rainfall and winds
00:06 EDT
Severe thunderstorms that ravaged the Hunter region and the Central Coast of New South Wales are over, the Bureau of Meteorology says, but Ausgrid and SES volunteers are still working to repair the damage.
