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
20:40 CST
21°C
32°C
Mostly sunny
Weather News
Weather warning: Suspected tornado hits Perth's north as storm sweeps through
19:04 EST
Trees are down and building damage has been reported after a suspected tornado ripped through Perth's northern suburbs, as an intense cold front hits Western Australia's south.
Stormy end to a wet month in Perth
14:36 EST
A blustery cold front is battering the nation's southwest today, threatening Perth and surrounding areas with damaging winds, thunderstorms and hail.
Record-July heat across multiple states and territories
13:02 EST
A large portion of northern and central Australia just experienced its warmest July on record in terms of maximum temperatures.
