Southeast Australian rainfall outlook

Issued 18 December 2013

A drier season likely for NSW, but a wetter one likely for Tasmania

Summary

  • A drier than normal season is more likely for NSW and northeast Victoria
  • A wetter than normal season is more likely for southern Tasmania
  • Climate influences include a neutral tropical Pacific, and a warm Indian Ocean
  • Outlook accuracy is moderate over most of southeastern Australia, but limited in western Tasmania, northeast and northwest NSW and parts of SA. See outlook accuracy tab for more information.
Probability of exceeding median rainfall, large image

Details

The chances of exceeding the median rainfall during the January to March period are 30 to 40% over most of NSW and northeast Victoria. In other words, the chances of below average rainfall are 60 to 70% over these areas: for every ten summer outlooks with similar odds to these, about six or seven of them would be below average and about three or four of them would result in above-average rainfall.

Conversely, the chance of exceeding the median rainfall is greater than 60% over the southern half of Tasmania. Elsewhere across southeast Australia, the chances of a wetter or drier than normal season are roughly equal.

Climate influences

The El Niño-Southern Oscillation (ENSO) remains neutral, with the majority of atmospheric and oceanic indicators close to their long-term average. Dynamical models surveyed by the Bureau suggest ENSO-neutral conditions are likely to persist at least for the austral summer and early autumn. This means there is no strong shift in the odds from the tropical Pacific in this outlook.

Although the Indian Ocean Dipole has limited impact upon Australia during the months from December to April, the broad area of warmer than average sea surface temperatures across the central Indian Ocean has been shown to influence the climate over large parts of Australia at this time of year.

Lower surface pressures are likely to bring cooler and potentially wetter conditions to parts of southern Australia (such as Tasmania and parts of southwest WA) early in the outlook period.

How accurate is the outlook?

Outlook accuracy for the January to March period is:

  • Moderate over most of Victoria, much of NSW, northeast Tasmania, and western SA
  • Weak over northeast NSW, northwest NSW, most of SA, and most of Tasmania