Southeast Australian rainfall outlook

Issued 26 March 2014

Drier season more likely for northeast New South Wales; wetter for southwest parts of SA

Summary

  • A drier than normal season is more likely for parts of northeast NSW
  • A wetter than normal season is more likely for western agricultural parts of SA
  • Climate influences include a warming tropical Pacific, and a warm to near-normal Indian Ocean
  • Outlook accuracy is moderate to high over most of southeast Australia except for northwest NSW, where accuracy is low.
Probability of exceeding median rainfall, large image

Details

The chances of exceeding the median rainfall during April to June are 35 to 40% over parts of northeast NSW. In other words, the chances of below average rainfall are 60 to 65% over these areas. For every ten April to June outlooks with similar odds to these, about four of them would result in above-average rainfall over these areas, while about six would be below average.

Conversely, the chance of exceeding the median rainfall is greater than 60% over western agricultural parts of SA.

Over the rest of southeast Australia, there is no significant shift in the odds towards either a wetter or drier than normal season.

Climate influences

The El Niño-Southern Oscillation (ENSO) currently remains neutral, but the tropical Pacific is currently warming. Dynamical models surveyed by the Bureau indicate that further warming of the tropical Pacific is likely in the coming months, with most models approaching or exceeding El Niño thresholds during the southern winter.

Sea surface temperatures surrounding Australia, and to the west, are expected to be near normal to warmer than normal. The warmer waters to the west of the continent may lead to increased evaporation and cloudiness, and thus explain the wetter than normal outlook for parts of the west. The Indian Ocean Dipole (IOD) influence is minimal during the first part of the outlook period, with a neutral IOD likely for the second part.

How accurate is the outlook?

Outlook accuracy for the April to June period is:

  • Moderate to high over most of southeast Australia, except for
  • northwest NSW, where accuracy is low