Water Week

EWN Publishing

Sunburnt country: 60 to 70 per cent chance of a dry October to December 2007 for South Eastern Australia

Posted by waterweek on 4 October 2007

South Eastern Australia and Tasmania and the far southeastern coastal fringe of the mainland had a 30 to 40 per cent chance of exceeding the three-month median rainfall. This means that below-normal falls have a 60 to 70per cent chance of occurring. Over most remaining parts of the country the chances of accumulating at least average rain for the December quarter are between 50 and 60per cent.

Seasonally dry in SW WA: The national outlook for total rainfall over the December quarter (October to December), shows contrasting odds between the west and southeast of the country. Higher seasonal falls are indicated in western WA while a drier than average season is more probable in the far southeast of the country. It should be noted though, that the December quarter is a seasonally dry time of year in northwest WA, with heavy rain being uncommon.

Cause of dry Spring: The pattern of seasonal rainfall odds across Australia is mainly a result of continuing higher than average temperatures over parts of the tropical and sub-tropical Indian Ocean.

The forecast: The chances of exceeding the median rainfall for the October to December period are between 60 and 70per cent over much of western to central WA. So for every ten years with ocean patterns like the current, about six or seven December quarters are expected to be wetter than average in this part of the country, while about three or four are drier. A small part of north-central Queensland also has a 60per cent chance of a wetter than average season.

There has been further gradual cooling of the equatorial Pacific during the past month, with cool anomalies consistent with a developing La Niña present in central and eastern areas. The 30-day value of the Southern Oscillation Index (SOI) was +6 as at 22nd September.

The following climate meteorologists in the National Climate Centre can be contacted about this outlook: Grant Beard on (03) 9669 4527, Lyn Bettio on (03) 9669 4165, David Jones on (03) 9669 4085.http://www.bom.gov.au/climate/ahead/rain_ahead.shtml

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