|Southeastern Aust Seasonal Rainfall Outlook: probabilities for May to July 2009, issued 24th April 2009|
Higher seasonal rainfall favoured in northeast NSW
For southeastern Australia, the outlook for total rainfall over the late autumn to mid-winter period (May to July), shows a moderate shift in the odds favouring a wetter than normal season across the northeast half of NSW.
The pattern of seasonal rainfall odds across southeastern Australia is mainly a result of warm conditions in the Indian Ocean in January and March; the Pacific Ocean had little contribution to this forecast.
For the May to July period, the chance of exceeding median rainfall is between 60 and 70% over the northeast half of NSW (see map). 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 over this area, while about three or four years are expected to be drier.
Across the rest of southeastern Australia, the chance of exceeding the median rainfall during the coming three months is between 40 and 60%, meaning that above average falls are about as equally likely as below average falls in these regions.
New: Under the WATL part of the Bureau's website, there is an expanded set of seasonal rainfall outlook maps and tables, including the probabilities of seasonal rainfall exceeding given totals (e.g. 200 mm).
Outlook confidence is related to how consistently the Pacific and Indian Oceans affect Australian rainfall. During May to July, history shows this effect to be moderately consistent over most of the northeastern half of NSW, parts of southern Victoria, northeastern SA and all of Tasmania. However, the effect is only weakly to very weakly consistent in a band stretching from northern of South Australia (encompassing most of the state) across to southeast NSW and covers most of Victoria. This also includes small patches included in northern NSW (see background information). In these areas where outlook confidence is not high, caution should be used when interpreting these outlooks.
Pacific climate patterns are currently neutral and the consensus from computer models is for near average tropical Pacific surface temperatures in the middle of the year, although with some warming from present values. The SOI is approximately +8 for the 30 days ending 21 April. 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 detailed forecast maps, including the probabilities of seasonal rainfall exceeding given totals, can be found here.
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 26th May 2009