|National Seasonal Rainfall Outlook: probabilities for Summer 2008/2009, issued 26th November 2008|
Wetter summer favoured in the west and far east
The national outlook for total rainfall over summer (December to February) shows a moderate shift in the odds favouring higher than normal totals over western WA as well as in parts of far northeast of NSW and southeast Queensland.
The pattern of seasonal rainfall odds across Australia is mainly a result of continued warmth in the central and southeastern Indian Ocean, especially off the west coast of WA.
The chance of exceeding median rainfall over Australia this summer is between 60 and 70% over a large part of western to central WA and between 60 and 65% over a small area in the far northeast of NSW extending into southeastern Queensland. This means that for every ten years with ocean patterns like the current, about six or seven years are expected to be wetter than average in these regions, while about three or four years are expected to be drier.
Across the rest of the country, the chance of exceeding the median rainfall this summer is between 40 and 60%, meaning that above average falls are about as equally likely as below average falls in these regions.
Outlook confidence is related to how consistently the Pacific and Indian Oceans affect Australian rainfall. During summer, history shows this effect to be moderately consistent across much of WA and scattered areas in eastern Australia, but the effect is generally only weakly or very weakly consistent through the centre of the country (see background information).
The tropical Pacific Ocean remains ENSO-neutral. Sea surface temperatures across most of the equatorial Pacific are near normal, although cool sub-surface temperatures persist in the eastern half of the basin. The SOI remains positive at approximately +14 for the 30 days ending 23 November. Computer models indicate that neutral conditions are likely to continue through summer. For routine updates and comprehensive discussion on any developments please see the ENSO Wrap-Up.
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: Lynette Bettio on (03) 9669 4165, Blair Trewin on (03) 9669 4623, Robyn Gardiner on (03) 9669 4671,|
Regional commentary is available from the Climate Services Sections in the Bureau's Regional Offices:
THE NEXT ISSUE OF THE SEASONAL OUTLOOK IS EXPECTED BY 17th December 2008