Northern Australian temperature outlook

Issued 24 July 2013

Contrasting outlook: cool days in the south, warm in the north

Text details of chance of warmer maximum and minimum temperatures

Summary

  • Warmer than normal days and nights are likely for most of the northern tropics
  • Cooler than normal maximum temperatures are forecast for the southern NT and southern Queensland
  • Near equal chance of above or below normal minimum temperatures across the Alice Springs district and central Queensland
  • The main climate drivers for this outlook include a negative Indian Ocean Dipole, a neutral-to-cool tropical Pacific, and warm sea surface temperatures around most of Australia
  • Outlook accuracy for the maximum temperature outlooks is moderate over the Top End of the NT, and most of Queensland, with the minimum temperature outlook moderate over most of northern Australia.
Probability of exceeding median maximum temperature, larger view Probability of exceeding median minimum temperature, larger view

Details

The chances of the August to October maximum temperature exceeding the long-term median maximum temperature are greater than 60% over the tropical north. Such odds mean that for every ten years with similar climate patterns to those currently observed, about six to eight August to October periods would be expected to be warmer than average over these areas, while about two to four years would be cooler.

Conversely, there is a 20 to 40% chance of warmer than normal days over the southern NT, and the southern half of Queensland. In other words, there is a 60 to 80% chance of cooler than normal days over these areas.

The chance that the average minimum temperature for August to October will exceed the long-term median minimum temperature is in excess of 60% over the tropical north; probabilities exceed 80% over much of the Top End of the NT and Cape York Peninsula.

There is a 25 to 40% chance of warmer than normal nights over southeast Queensland (60 to 75% chance of cooler than normal nights).

Climate influences

A negative Indian Ocean Dipole (IOD) event is in progress, and is expected to persist through spring 2013. A negative IOD event tends to increase temperatures over northern Australia.

In the first half of the northern dry season, much of tropical northern Australia experienced stronger than normal easterly winds, thus decreasing the strength and duration of the southerly wind bursts that usually bring typical "dry season" weather conditions. The flow-on effects include increased humidity and, when averaged across the season, warmer than average maximum and minimum temperatures. The current seasonal outlook suggests this pattern will continue.

The tropical Pacific is ENSO-neutral. The dynamical seasonal outlook model suggests a brief period of weak La Niña-like conditions forming during the next few months. This has contributed to an increased chance of above normal rainfall for northern and eastern Australia. However, international climate models surveyed by the Bureau of Meteorology suggest ENSO-neutral is the most likely outcome over the coming season, with the Bureau model being the coolest (most La Niña-like).

Sea surface temperatures off the Top End are generally warmer than normal, which will tend to influence air temperatures along the coast.

How accurate is the outlook?

Outlook accuracy is related to how consistently the oceans and broadscale climate affect Australian temperatures. During the August to October period, historical accuracy shows the outlook for maximum temperatures to be moderately consistent over the Top End of the NT, and most of Queensland. Elsewhere, it is weakly to very weakly consistent.

For minimum temperatures, historical accuracy is moderately consistent over most of northern Australia.