National rainfall outlook

Issued 24 July 2014

Drier than normal signal persists in parts of the east

Text commentary of chance of increased rainfall

Summary

  • A drier than normal season is more likely for northern Queensland, and parts of southeast Australia
  • A wetter than normal season is more likely for a small part of central Australia
  • Climate influences include a brief negative Indian Ocean Dipole, and near-average Pacific waters
  • Outlook accuracy is moderate to high over most of the eastern States, the NT, SA and patchy over WA.
  • Details are summarised in our new monthly Climate and Water Outlook video
Probability of exceeding median rainfall - click on the map for a larger version
Probability of exceeding median rainfall, large image

Details

The chances of receiving above median rainfall for August to October are less than 40% over northern Queensland, southern NSW, the far southeast of SA, and most of Victoria. In other words, this means the chances of below median rainfall is greater than 60% in these areas. For every ten August to October outlooks with similar odds to these, about three or four of them would result in above-average rainfall over these areas, while about six or seven would be below average.

Over the rest of the country, there is no significant shift in the odds towards either a wetter or drier than normal season; the main exception is an increased chance of a wetter season over parts of the red centre.

Climatologically, areas of tropical northern Australia have at least two months of the dry season left. This means that the median rainfall at this time of the year is far less than during the summer months (see the Rainfall averages tab).

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 the eastern States, the NT, SA, and parts of WA
  • Low to very low over the WA interior, and small parts of central Queensland

Related links

Climate