National outlook: drier forecast for south and west

Beef Central, 21/07/2011

Drier than normal conditions are forecast for western and southern parts of the country from August to October, according to the latest national three month outlook. Click on images below story to view maps in larger format. The latest three-month seasonal outlook from the Bureau of Meterology forecasts increased chances of drier than normal conditions over parts of the west and south of Australia.

The forecasts are contained in the national outlook for August to October released today.

The outlook indicates a “moderate shift” towards a drier than normal season in the west and south, while it shows no strong shift in the odds of drier than normal conditions across the north or east.

The pattern of seasonal rainfall odds across Australia is produced using recent Pacific and Indian Ocean temperature patterns. 

The outlook factors in the decline of La Niña conditions across the Pacific during the previous season, as well as the persistence of above average temperatures over key parts of the Indian Ocean.

The chances of receiving above median rainfall August to October period are between 30pc and 40pc over western WA, much of SA, western NSW and northwestern Victoria.

“Such odds mean that for every 10 years with similar ocean patterns to those currently observed, about three to four August to October periods would be expected to be wetter than average over this area, while about six to seven would be drier,” the outlook statement said.

“However, the outlook skill is not high over these regions, so this outlook should be used with caution.”

Temperature outlook

The national outlook for maximum and minimum temperatures averaged over August to October shows a moderate to strong shift in the odds favouring higher than average temperatures across most of Australia.

This outlook is primarily a result of warm conditions in the Indian Ocean.

The chance that the average August to October maximum temperature will exceed the long-term median maximum temperature is above 60pc across Australia apart from the northern tropics.

Probabilities exceed 80pc over southern and western WA. This means that for every ten years with ocean patterns like the ones currently observed, about six to eight August to October periods would be expected to be warmer than average in these areas, with about two to four being cooler.

The chance that the average minimum temperature for August to October will exceed the long-term median minimum  temperature is above 60pc in WA, SA, Victoria, Tasmania, most of NSW, the western half of Queensland, and most of the NT. Probabilities exceed 80pc over the southern half of WA.

History shows the oceans' effect on minimum temperatures during the August to October period to be consistent to moderately consistent over Queensland, western NSW, parts of SA, the southern half of WA and the Top End. Elsewhere, the effect is only weakly or very weakly consistent.


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