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
17:30 CST
31°C
22°C
Mostly sunny
Weather News
Near-record dry start to winter
16:24 EST
Australia is entering what many are hoping won't be a dry July after the nation's second driest and seventh warmest June on record.
Winter arrives in SA
14:17 EST
Wintry weather is affecting southern districts of South Australia today after an unusually dry and calm start to the season.
Bluff Knoll locals, tourists brave freezing temperatures to frolic in 'fluffy' snow
16:17 EST
The Great Southern peak of Bluff Knoll is snow capped, with locals saying it is the heaviest snowfall in years.
