|National Seasonal Rainfall Outlook: probabilities for May to July 2009, issued 24th April 2009|
Higher seasonal rainfall favoured in parts of north & east Australia
The national 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 in parts of northern and eastern Australia.
The pattern of seasonal rainfall odds across 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% in a region covering the northeast half of NSW and most of southern Queensland (see map). In addition parts of the NT and WA also have 60 to 65% chances of a wetter than normal three months, although some of this region is seasonally dry at this time of year. 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 these parts in the north and east, while about three or four years are expected to be drier.
Across the rest of the country, 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 the May-July period, history shows this effect to be moderately consistent in a band from the central Northern Territory across most of the southern two-thirds of Queensland, as well as the northeastern half of NSW. Moderate consistency is also evident in much of Tasmania, parts of southern Victoria, and patches through the interior of Western Australia. Elsewhere the effect is only weakly or very weakly consistent (see background information).
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.
|The following climate meteorologists in the National Climate Centre can be contacted about this outlook: Grant Beard on (03) 9669 4527, Brad Murphy on (03) 9669 4409, Blair Trewin on (03) 9669 4623.|
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 26th May 2009