|National Seasonal Rainfall Outlook: probabilities for November 2006 to January 2007, issued 26th October 2006|
Mixed rainfall outlook for late spring to mid-summer
The latest seasonal rainfall outlook issued by the Bureau of Meteorology, shows a mixed pattern of odds for exceeding the median rainfall over the late spring to mid-summer period (November-January). Drier than normal conditions are indicated for SE Queensland and much of NSW, whereas above average three-month totals are favoured in western and northern Queensland and in northwest WA.
The pattern of seasonal rainfall odds across Australia is a result of higher than average temperatures in both the Pacific and Indian Oceans. The warm Pacific biases the climate towards drier than average across eastern and northern Australia, but the warm Indian Ocean promotes wetter than average conditions across the tropics and in western WA.
The chances of exceeding the median rainfall for the November to January period, are between 30 and 40% over the eastern half of NSW and in SE Queensland, with a few areas having 25 to 30% chances. These probabilities mean that BELOW median falls have about a 60 to 75% chance of occurring.
So in years with ocean patterns like the current, about six or seven November to January periods out of ten are expected to be drier than average in these parts of eastern Australia, with about three or four out of ten being wetter.
In contrast, two regions - one covering parts of north and west Queensland and the other extending from the northwest to the interior of WA, have a 60 to 65% chance for the three-month rainfall total to exceed the long-term median. This equates to six seasons being wetter than average and four drier for every ten years with ocean temperatures similar to the present.
Outlook confidence is related to how consistently the Pacific and Indian Oceans affect Australian rainfall. During the November to January period, history shows this effect to be moderately consistent across much of Tasmania, NSW, Queensland and the NT, but generally weakly consistent elsewhere (see background information).
The Southern Oscillation Index (SOI), negative for the fifth straight month, rose from −16 in August to −5 in September. The approximate SOI for the 30 days ending 23rd October was −14.
The current El Niño conditions, of which the low SOI is but one indicator, are very likely to persist for the rest of 2006, which would qualify it as an official El Niño event. 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 Sections in the Bureau's Regional Offices:
THE NEXT ISSUE OF THE SEASONAL OUTLOOK IS EXPECTED BY 23rd NOVEMBER 2006