Northern Australian rainfall outlook

Issued 27 November 2013

Drier summer more likely for parts of northeast Australia

Summary

  • A drier than normal season is more likely for much of northeast Australia
  • The chances of a wetter or drier than normal season are roughly equal over most of the Northern Territory and the western Queensland Border
  • Climate influences include a neutral tropical Pacific, and local sea surface temperature patterns
  • Outlook accuracy is moderate over most of eastern Queensland, and the Top End of the NT. Elsewhere, outlook accuracy is low.
Probability of exceeding median rainfall, large image

Details

The chances of exceeding the median rainfall during December to February are 30 to 40% over eastern Queensland, and the eastern Top End of the NT. In other words, the chances of below average rainfall are 60 to 70% over these areas. So, for every ten December to February 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.

The chance of receiving a wetter or drier than normal December to February is roughly equal (i.e., close to 50%) over the remainder of northern Australia.

Climate influences

The tropical Pacific has remained ENSO-neutral since mid-2012. The dynamical seasonal outlook model suggests ENSO-neutral conditions will remain at least for the next three months. This means there is no strong shift in the odds from the tropical Pacific in this outlook.

With major climate influences likely to remain neutral (and hence have lesser impact upon Australia) over the coming months, secondary influences, such as sea surface temperature patterns, persistent pressure systems, and changes in wind patterns around the Australian continent are tending to drive the Australian climate. While these shorter-term fluctuations are less predictable, the model still shows moderate skill in seasonal temperature forecasts for most of northern Australia.

How accurate is the outlook?

Outlook accuracy is related to how consistently the oceans and broadscale climate affect Australian rainfall. During the December to February period, historical accuracy shows the outlook to be moderately consistent over most of eastern Queensland, and the Top End of the NT. Elsewhere, the outlook is weakly consistent.