Southeast Australian rainfall outlook

Issued 25 June 2014

A drier July to September period more likely for New South Wales

Summary

  • A drier than normal season is more likely for New South Wales
  • A wetter than normal season is more likely for some parts of eastern Tasmania and eastern Victoria
  • Climate influences include warm Indian and Pacific oceans
  • Outlook accuracy is moderate over most of New South Wales, Victoria, western Tasmania and northeast SA and low to very low across western NSW and through central and eastern parts of SA. See accuracy tab for more information.
Probability of exceeding median rainfall, large image

Details

The chances of receiving above median rainfall for July to September are less than 40% over most of NSW, and less than 30% in the inland northeast of NSW. In other words, these areas have a greater than 60% chance of below average rain. For every ten July to September periods with similar odds to these, at least six of them would have below-average rain.

There is an increased chance of a wetter than normal season over eastern Tasmania and parts of eastern Victoria. Over South Australia, most of Victoria and much of Tasmania there is not a significant shift in the odds towards either a wetter or drier than normal season.

Climate influences

Warming of the tropical Pacific Ocean over the past several months has primed the climate system for an El Niño in 2014. However, in the absence of the necessary atmospheric response, the increase in Pacific Ocean temperatures has levelled off in recent weeks. Despite some easing in the model outlooks, international climate models surveyed by the Bureau still indicate El Niño is likely to develop by spring 2014. While POAMA, the model that produces the seasonal outlooks, does not forecast a high probability of El Niño, it retains a drier signal across the country due to patterns in the ocean and atmosphere across the Pacific. This drier signal is consistent between international models regardless of their ENSO forecast.

Models indicate the currently warm Indian Ocean is likely to remain warm. The Indian Ocean Dipole (IOD) is expected to remain neutral for the next three months, and is therefore unlikely to have a significant influence upon this outlook.

How accurate is the outlook?

Outlook accuracy for the July to September period is:

  • Moderate over most of New South Wales, Victoria, western Tasmania and northeast SA
  • Low to very low across western NSW and through central and eastern parts of SA