Western Australian temperature outlook

Issued 25 September 2013

Warmer days and nights more likely for most of Western Australia

Text details of chance of warmer maximum and minimum temperatures

Summary

  • Warmer days and nights are more likely over most of WA with strongest odds over northwest
  • Climate influences include a neutral Indian Ocean Dipole, a neutral tropical Pacific, and locally warm sea surface temperatures
  • Outlook accuracy for maximum temperatures is moderate to high over most of WA excluding western parts, with minimum temperature accuracy moderate to high over most of WA, excluding northern parts.
Probability of exceeding median maximum temperature, larger view Probability of exceeding median minimum temperature, larger view

Details

The chances of the October to December maximum temperature exceeding the long-term median maximum temperature are greater than 60% over most of WA excluding the east Kimberley and eastern Interior. Odds increase to greater than 70% over northwest. Such odds mean that for every ten years with similar climate patterns to those currently observed, about six to seven October to December periods would be expected to be warmer than average over these areas, while about three to four years would be cooler.

The chances that the average minimum temperature for the October to December period will exceed the long-term median minimum temperature are 60% to 70% over most of WA.

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 accuracy 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 moderately-to-highly consistent over most of WA, except for parts of the west.

The effect on minimum temperatures during this season is moderately consistent over most of WA, except for the Gascoyne, Pilbara and Kimberley regions where the effect is only weakly to very weakly consistent.