Southeast Australian rainfall outlook

Issued 24 July 2014

A drier August to October period more likely for some parts of Southeast Australia

Summary

  • A drier than normal season is more likely for central and western parts of Victoria, south-central NSW and southeast SA
  • A wetter than normal season is more likely for the far northwest pastoral districst of SA
  • Climate influences include a brief negative Indian Ocean Dipole, and near-average Pacific waters
  • Outlook accuracy is moderate to high over most Southeast Australia excluding the far west and south-central parts of SA and the lower southeast of NSW. See accuracy tab for more information.
  • Details are summarised in our new monthly Climate and Water Outlook video
Probability of exceeding median rainfall, large image

Details

The chances of receiving above median rainfall for August to October are less than 40% over southern NSW, central and western parts of Victoria, and southeast SA. In other words, the chances of below median rainfall is greater than 60% in these areas. For every ten August to October 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 the far northwest pastoral parts of SA and northeast Tasmania. Over the remainder of southeast Australia 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, Pacific Ocean temperatures have either stabilised, or some cooling has occurred. Despite some further easing in the model outlooks, a majority of international climate models still indicate El Niño is likely to develop during spring 2014. While there are some differences in ENSO outlooks, the near-average to drier-than-average signal across eastern Australia is generally consistent between international models.

The Indian Ocean Dipole (IOD) index has been below −0.4°C (the negative IOD threshold) since mid-June. Model outlooks suggest the IOD is likely to return to neutral by spring. A negative IOD typically brings wetter winter and spring conditions to inland and southern Australia. It is possible that the effects of the Indian Ocean and Pacific are competing to some degree, minimising the likelihood of broader rainfall signals.

How accurate is the outlook?

Outlook accuracy for the August to October period is:

  • Moderate to high over most of New South Wales, Victoria, Tasmania and northern and eastern SA
  • Low to very low across the far west and south-central SA and the lower southeast of NSW