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
12:40 CST
33°C
26°C
Possible thunderstorm
Weather News
Sydney's neverending heat
14:09 EDT
As school goes back this week the scorching summer-holiday-heat is sticking around.
Wrap up of the Tropical Low
12:31 EDT
A tropical low is now continuing off WA's Pilbara coast and weakening over the Indian Ocean.
WA cyclone: BOM gives Pilbara residents all clear for tropical low
21:44 EDT
People in parts of Western Australia's Pilbara region are given the all clear by the Bureau of Meteorology (BOM) regarding a tropical low that earlier prompted a blue alert.
