Southeastern Australian temperature outlook

Issued 22 May 2013

Warmer nights likely for much of southeast Australia

Text details of chance of warmer maximum and minimum temperatures

Summary

  • Warmer than normal days are more likely in Tasmania and southern Victoria, with cooler days more likely across most of NSW and SA
  • Warmer than normal nights are more likely across most of southeast Australia
  • Climate influences include a warmer than normal eastern Indian Ocean, a neutral tropical Pacific, and warmer than average sea surface temperatures around much of the coastline
  • Skill for maximum temperatures is moderate over most of southeast Australia, with lower skill in western SA, while minimum temperature skill is moderate over most of southeast Australia.
Probability of exceeding median maximum temperature, large image Probability of exceeding median minimum temperature, large image

Details

The chances that the winter maximum temperature will exceed the long-term median are greater than 60% in southern Victoria, with probabilities greater than 80% in Tasmania (see map above). 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.

Conversely, there is a 30 to 40% chance of warmer than normal days over the most of SA and NSW. In other words, there is a 60 to 70% chance of cooler than normal days over these areas.

The chance that the average minimum temperature for winter will exceed the long-term median minimum temperature is greater than 60% over most of southeast Australia, with the exception of northern SA, where the chances of a warmer or cooler winter are roughly equal.

Climate influences

The tropical Pacific has remained ENSO-neutral since mid-2012. Climate models surveyed by the Bureau of Meteorology suggest sea surface temperatures in the tropical Pacific Ocean are likely to sit on the cool side of neutral during winter 2013.

Four of five international models surveyed by the Bureau favour the development of a negative Indian Ocean Dipole (IOD) event during winter-spring 2013. A negative IOD during winter-spring increases the chances of above normal rainfall, and thus cloud amount, over southern Australia. Increased cloudiness reduces sunshine hours, and hence daytime temperatures, over inland Australia.

Warmer than normal ocean surface temperatures currently surround much of the continent. Warmer ocean temperatures will tend to influence air temperatures in those areas closer to the coast.

How accurate is the outlook?

Outlook confidence is related to how consistently the oceans and broadscale climate affect Australian temperatures. During winter, model accuracy shows the outlook for maximum temperatures to be weakly consistent in western SA, but moderately to strongly consistent over the rest of southeast Australia.

The effect on minimum temperatures during this season is moderately consistent over most of southeast Australia, but weakly consistent in parts of northwest NSW.