|Southeastern Aust Seasonal Rainfall Outlook: probabilities for Spring 2008, issued 26th August 2008|
Neutral spring outlook for much of southeastern Australia
The outlook for total spring (September to November) rainfall is neutral for much of southeastern Australia, but there are moderate swings in the odds towards below normal rainfall in an area covering eastern South Australia and far southwestern NSW.
The pattern of seasonal rainfall odds for southeastern Australia does not reflect any strong contribution from the Pacific or Indian Oceans. In particular, the equatorial Pacific is generally in a neutral state, and although there is warming in the central and southeastern Indian Ocean, this is not contributing strongly to the rainfall outlook for southeastern Australia.
Over most of southeastern Australia, the chances of September to November totals exceeding the 3-month median rainfall are close to 50% (see map): the chances of being wetter than normal are about the same as the chances of being drier.
However, the chances of exceeding the median rainfall over the September to November period drop to between 35 and 40% over parts of central and eastern South Australia and far southwestern NSW. This means the chances of below average rainfall are between 60 and 65% in these areas. So for every ten years with ocean patterns like the current, about six springs are expected to be drier than average in these parts of southeastern Australia, while about four are likely to be wetter.
Outlook confidence is related to how consistently the Pacific and Indian Oceans affect Australian rainfall. During spring, history shows this effect to be moderately consistent over most of Victoria and inland NSW, northern Tasmania and large parts of eastern SA. Elsewhere the effect is only weakly or very weakly consistent (see background information). In these areas where outlook confidence is not high caution should be used when interpreting these outlooks.
The approximate 30-day value of the Southern Oscillation Index (SOI) was +3 as at 23 August, while a mixed pattern of warmer and cooler than normal temperatures persists along the equatorial Pacific Ocean. Both these observations indicate a neutral climate pattern across the Pacific, which computer models indicate is likely to continue for the next few seasons. For routine updates and comprehensive discussion on any developments please see the ENSO Wrap-Up.
Click on the map above for a larger version of the map. Use the reload/refresh button to ensure the latest forecast map is displayed.
More information on this outlook is available Monday to Friday from 9.00am to 5.00pm local time by contacting the Bureau's Climate Services sections in Queensland, NSW, SA, Victoria and Tasmania at the following numbers:
THE NEXT ISSUE OF THE SEASONAL OUTLOOK IS EXPECTED BY 25th September 2008