|WA Seasonal Rainfall Outlook: probabilities for Summer 2008/2009, issued 26th November 2008|
Wetter summer favoured for western to central WA
The Western Australia outlook for total rainfall over summer (December to February) shows a moderate tendency in the odds to favour higher than normal totals over western to central WA.
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 this summer is between 60 and 70% over a large part of western to central WA. 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.
For the remainder of the state, the chance of exceeding the median rainfall this summer is between 50 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, but to be weakly consistent in parts of southern and eastern WA (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.
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|More information on this outlook is available from 8.30am to 4.30pm (WST) Monday to Friday by contacting the Climate Services Centre in the Bureau's Perth Office: (08) 9263 2222.|
THE NEXT ISSUE OF THE SEASONAL OUTLOOK IS EXPECTED BY 17th December 2008