Southeast Australian temperature outlook

Issued 25 September 2013

Warmer days and nights likely for much of southeast Australia

Text details of chance of warmer maximum and minimum temperatures

Summary

  • Warmer than normal days and nights are more likely over most of southeast Australia, with strongest odds in Tasmania.
  • Climate influences include a neutral Indian Ocean Dipole, a neutral tropical Pacific, and locally warm sea surface temperatures
  • Outlook accuracy for maximum temperatures is high across most of southeast Australia while accuracy for minimum temperatures is generally moderate, with the exception of the NSW north coast where accuracy is low.
Probability of exceeding median maximum temperature, larger view Probability of exceeding median minimum temperature, larger view

Details

The chances that the October to December maximum temperature will exceed the long-term median maximum temperature are greater than 60% across most of southeast Australia, with odds greater than 70% in Tasmania and parts of the south and east coasts. Such odds mean that for every ten years with similar climate patterns to those currently observed, about six to eight years would be expected to be warmer than average over these areas, while about two to four years would be cooler.

The chance that the average minimum temperature for October to December will exceed the long-term median minimum temperature is greater than 60% over most of southeast Australia, with odds greater than 70% in Tasmania and southeast NSW.

Climate influences

The negative Indian Ocean Dipole (IOD) event that was influencing Australian climate through late autumn into winter has weakened over the past few weeks, with IOD-neutral values prevailing since early August. The majority of climate models indicate that the IOD will remain neutral through to the end of the year, suggesting that the 2013 negative-IOD is most likely at an end.

The tropical Pacific has remained ENSO-neutral since mid-2012. The dynamical seasonal outlook model suggests ENSO-neutral conditions will remain for the rest of 2013.

With the two main climate influences (ENSO and the IOD) likely to remain neutral (and hence have lesser influence upon Australia) over the coming months, secondary influences, such as warmer-than-normal oceans around the continent and a forecast for lower pressures over southeastern areas, are tending to drive the October-December Australian climate patterns.

How accurate is the outlook?

Outlook confidence is related to how consistently the oceans and broadscale climate affect Australian temperatures. During the October to December period, historical accuracy shows the outlook for maximum temperatures to be highly consistent across most of southeast Australia

The effect on minimum temperatures during this season is moderately consistent over most of southeast Australia, with the exception of the NSW north coast where the effect is only weakly to very weakly consistent.