|National Seasonal Rainfall Outlook: probabilities for January to March 2007, issued 20th December 2006|
Decreased rainfall in March quarter for Qld and northern NSW
The latest seasonal rainfall outlook issued by the Bureau of Meteorology shows a moderate shift in the odds towards below-normal March quarter (January to March) rainfall for much of Queensland and northern NSW. In contrast, a small region covering part of southwest Victoria and southeast SA has a moderate swing in the odds towards above average seasonal rainfall. However, the confidence in the outlooks at this time of year is rather low, so these outlooks should be used with caution.
The pattern of seasonal rainfall odds across Australia is mostly a result of higher than average temperatures in the Pacific Ocean (because of El Niño).
The chances of exceeding the median rainfall for the January to March period, are between 30 and 40% across eastern Australia east of a line from Sydney to Wanaaring to Cloncurry to Townsville. This means that BELOW median falls have about a 60 to 70% chance of occurring. So in years with ocean patterns like the current, about six or seven March quarters out of ten are expected to be drier than average over this part of the country, with about three or four out of ten being wetter.
In contrast, the chances of exceeding the median rainfall for the March quarter are between 60 and 65% over southwest Victoria and a narrow coastal strip in southeast SA. Over the rest, and majority, of the country, the chances are between 40 and 60% for a wetter than normal March quarter.
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 through eastern parts of NSW and Queensland, large parts of the NT and over much of southern and western WA. Elsewhere the effect is only weakly or very weakly consistent (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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|The following climate meteorologists in the National Climate Centre can be contacted about this outlook: Grant Beard on (03) 9669 4527, Lyn Bettio on (03) 9669 4165, David Jones on (03) 9669 4085.|
Regional commentary is available from the Climate Services Centres in the Bureau's Regional Offices:
THE NEXT ISSUE OF THE SEASONAL OUTLOOK IS EXPECTED BY 23rd JANUARY 2007