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
16:50 CST
30°C
18°C
Sunny
Weather News
Further heavy rain for SE QLD, NE NSW
11:57 EST
Rainfall totals from the current spell of wet weather could more than double over the next few days as a low pressure trough lingers over parts of northeast New South Wales, with shifting across the border into Queensland from this afternoon.
Sydney fog causes some public holiday flight delays
09:30 EST
Sydneysiders have woken to a classic pea-souper blanketing the city, with the thick fog forcing the cancellation of flights in and out of Sydney Airport.
Widespread fog causing headaches across southeastern Australia
07:09 EST
Fog and low cloud is causing travel headaches in Queensland, New South Wales, the ACT, Victoria and South Australia.
