Water Week

EWN Publishing

Blistering heat ahead for Southeastern Australia – October to December 2007

Posted by waterweek on 4 October 2007

The Government forecast issued 25th September 2007 showed the outlook was for blistering heat across tthe Murray Darling Basin, with the highest heat for South Australia and Victoria.

Hotter than average: “In southeastern Australia, the outlook for maximum temperatures averaged over the December quarter (October to December) shows a moderate to strong shift in the odds favouring hotter than average conditions. The pattern of seasonal temperature odds across southeastern Australia is mainly a result of continuing higher than average temperatures over parts of the tropical and sub-tropical Indian Ocean.

60-80pc chance of a sizzler: Averaged over the December quarter, the chances are between 60 and 80 per cent for above-normal maximum temperatures over NSW, Tasmania, most of SA and parts of northern and eastern Victoria (see map). Across western and central Victoria, together with southeastern SA, the chances exceed 80 per cent So for every ten years with ocean patterns like the current, about six to eight October to December periods are expected to be warmer than average over southeastern Australia, with about two to four being cooler.

Blame the hot oceans: Outlook confidence is related to how consistently the Pacific and Indian Oceans affect Australian temperatures. During the December quarter, history shows this effect on maximum temperatures to be moderately consistent across large parts of southeast Australia.

Mins high, too: Minimum temperatures for the December quarter are favoured to be warmer than normal across the north of both SA and NSW, where the chances of increased overnight warmth (averaged over the coming three months) are mainly between 60 and 65 per cent;

How much can you rely on the forecast? Across the rest of the southeast, the probabilities are between 50 and 60 per cent . History shows the oceans’ effect on minimum temperatures during October to December to be moderately to highly consistent over most of western and northern NSW, northern SA and in patches of both Victoria and Tasmania. In southeast SA, southeast NSW, most of Victoria and central Tasmania, the effect is generally weakly consistent.
 
The Australian impacts of 23 El Niño events since 1900 are summarized on the Bureau’s web site (www.bom.gov.au/climate/enso/).

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