Agriculture Weather


Southern Oscillation Index

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  • Aus

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.

Southern Oscillation Index

SOI

Nino3.4 Index

Nino3.4
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Weather News

Rare blanketing for Launceston with more wild weather on the way

17:28 EST

Tasmania's wintry blast continued overnight, with Launceston in the state's north receiving its most significant snowfall since the early 1970s.

Rain looms for some drought-weary parts of Australia

17:22 EST

Useful rain will spread over South Australia, Victoria, NSW, and southern Queensland during the second half of this week.