|SA Seasonal Rainfall Outlook: probabilities for January to March 2007, issued 20th December 2006|
Neutral outlook for SA March quarter rainfall
Seasonal rainfall odds for the March quarter (January to March) do not strongly favour either wetter or drier than average conditions across most of South Australia, the Bureau of Meteorology announced today, although a slightly elevated chance of above average falls exists in parts of the southern region of the State. One exception is a narrow strip along the southeast coast where above average falls are favoured. However, the confidence in the outlooks at this time of year is rather low, so this outlook should be used with caution.
The pattern of seasonal rainfall odds across SA is a result of higher than average temperatures in the Pacific Ocean (because of El Niño) and the Indian Ocean. The warm Pacific promotes higher than normal seasonal falls in southeast SA, while the warm Indian has a weaker influence the other way. So the two effects tend to cancel each other.
The chances of exceeding the median rainfall for the January to March period, are mainly between 45 and 60% across South Australia, apart from a small region in the Southeast, and narrow coastal strip extending across the Fleuieu Peninsula, where the probabilities are over 60%. So in years with ocean patterns like the current, about six March quarters out of ten are wetter than average and four out of ten drier in these pockets with elevated odds.
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 only very weakly consistent through most of SA (see background information).
The Southern Oscillation Index (SOI), negative for the seventh straight month as a result of the El Niño, rose from −15 in October to −1 in November. The approximate SOI for the 30 days ending 17th December was −4.
The current Pacific El Niño pattern, of which the low SOI is but one indicator, is expected to persist for most of the summer. For routine updates and comprehensive discussion on the latest data relating to El Niño, together with details on what the phenomenon is and how it has affected Australia in the past, please see the ENSO Wrap-Up.
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|More information on this outlook is available from 9.00am to 5.00pm (CST) Monday to Friday by contacting the Climate and Consultancy section in the Bureau's Adelaide Office: (08) 8366 2664.|
THE NEXT ISSUE OF THE SEASONAL OUTLOOK IS EXPECTED BY 23rd JANUARY 2007