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
15:50 CST
32°C
25°C
Possible thunderstorm
Weather News
Southern storms
17:09 EDT
Severe thunderstorm warnings have been issued for parts of South Australia and Victoria this afternoon.
Tasmanian floods: BOM and SES lashed by farmers over weather warnings amid June deluge
17:04 EDT
Forecasting by the Bureau of Meteorology (BOM) and SES phone alerts during flooding in Tasmania last June have been criticised as inadequate.
North, central Queensland passenger rail down after heavy rain
16:54 EDT
There are major disruptions for rail passengers in central Queensland after large sections of the track were damaged following days of torrential rain.
