|WA Seasonal Rainfall Outlook: probabilities for January to March 2009, issued 17th December 2008|
Above average rainfall likely in southwest WA
The WA outlook for total March quarter rainfall (January to March), shows moderate to strong odds favouring higher than normal rainfall over southwest WA.
The pattern of seasonal rainfall odds across WA is mainly a result of continued warmth in the central Indian Ocean.
The chance of exceeding median rainfall during the March quarter are between 60 and 75% in much of southwest 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 this region, while about three or four years are expected to be drier.
For the remainder of the state, the chances of exceeding the median rainfall during the March quarter are between 45 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 the March quarter, history shows the effect to be moderately consistent over much of southern and western WA, as well as far eastern parts. Elsewhere the effect is only weakly or very weakly consistent. (see background information).
The tropical Pacific Ocean remains ENSO-neutral. Sea surface temperatures across most of the equatorial Pacific are near normal, however, cool sub-surface temperatures persist from the dateline to the South American coast and the trade winds are now stronger than normal across most of the basin. The SOI remains positive at approximately +13 for the 30 days ending 14 December. Most international computer models indicate that neutral conditions are likely to continue through summer and autumn, however, two models predict cooling. 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 22nd January 2009