National Seasonal Rainfall Outlook: probabilities for August to October 2004, issued 13th July 2004

Seasonal rainfall odds close to 50:50

There are no strong shifts in the odds towards either above or below average three-month falls for the August to October period, the Bureau of Meteorology announced today.

However, in the southeast of the country, near average rainfall in the next few months would fall well short of removing the rainfall deficits that have accumulated during the past two years. In fact, areas near Melbourne, southeast Victoria and the ACT would need record July to September rainfall just to elevate the total since July 2002 to the 10th percentile.

The current pattern of outlook probabilities is due to mainly near average temperatures in the Pacific and Indian Oceans.

For the whole country, the odds of above median rainfall are close to 50:50, meaning that they're too weak to offer any firm guidance as to the most likely outcome for late winter to mid-spring rainfall. So in years with ocean patterns like the current, about five August to October periods out of ten are expected to be wetter than average, with about five out of ten being drier.

probability of exceeding median rainfall - click on the map for a larger version of the map

However, it should be noted that in large parts of northern Australia, August to October is typically a dry time of year and heavy rain is uncommon during this period.

Outlook confidence is related to the influence of Pacific and Indian Ocean temperatures on seasonal rainfall. During August to October, history shows this influence to be moderately consistent across most of Queensland, the east and north of the NT and the northern inland of NSW. Elsewhere, it is generally weakly consistent, reaching moderate only in patches (see background information).

Both the Indian and tropical Pacific Oceans remain a little warmer than average. For more detail see the the El Niño Wrap-Up.

The Southern Oscillation Index (SOI) has continued its strongly fluctuating behaviour with a June value of –14, following the May reading of +13 and April's –15. The approximate SOI for the 30 days ending 10th July was –16.


Click on the map above for a larger version of the map. Use the reload/refresh button to ensure the latest forecast map is displayed.

The following climate meteorologists in the National Climate Centre can be contacted about this outlook: Grant Beard on (03) 9669 4527, David Jones on (03) 9669 4085, Robert Fawcett on (03) 9669 4296
Regional versions of this media release are available: | Qld | NSW | Vic | Tas | SA | WA | NT |

Regional commentary is available from the Climate and Consultancy Sections in the Bureau's Regional Offices:
Queensland -(07) 3239 8669 or (07) 3239 8666
New South Wales -(02) 9296 1522
Victoria -(03) 9669 4949
Tasmania -(03) 6221 2043
South Australia -(08) 8366 2664
Western Australia -(08) 9263 2222
The Northern Territory -(08) 8920 3813



Corresponding temperature outlook

June 2004 rainfall in historical perspective

April to June 2004 rainfall in historical perspective


Background Information