|National Seasonal Rainfall Outlook: probabilities for April to June 2009, issued 24th March 2009|
Mixed June quarter rainfall odds in the east and south
The national outlook for total June quarter rainfall (April-June), shows a mixed pattern of odds for exceeding the seasonal median, especially in the east and south. A wetter than normal season is favoured in parts of eastern NSW and Queensland, whereas a drier than normal three months is more likely in parts of SA, Victoria, southwest NSW and northern Tasmania.
The pattern of seasonal rainfall odds across Australia is mainly a result of warm conditions in the Indian Ocean in February; the Pacific Ocean had little contribution to this forecast.
For the April to June period, the chance of exceeding median rainfall is between 60 and 70% in a region covering much of eastern and northern NSW as well as southeast Queensland (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.
Conversely, the chance of above median falls is below 40% over northwest WA and in a band extending from northwest SA across southwest NSW and Victoria (except East Gippsland) to northern Tasmania (see map). The probabilities drop below 30% in central SA. This means that below median falls, i.e. drier than normal conditions, have a 60 to 75% chance of occurring across this broad region.
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).
Across the rest of the country, the chance of exceeding the median rainfall during the June quarter is between 40 and 60%, meaning that above average falls are about as equally likely as below average falls in these regions.
Outlook confidence is related to how consistently the Pacific and Indian Oceans affect Australian rainfall. During the June quarter, history shows this effect to be moderately consistent in a band from northwest WA across SA, the far southwest of NSW and over most of Victoria. Moderate consistency is also evident in southeast Queensland, northeast NSW, eastern Tasmania and patches in the NT. Elsewhere the effect is only weakly or very weakly consistent (see background information).
Pacific climate patterns were bordering on La Niña for several months, with above average wet season falls in the Australian tropics a direct result. The equatorial Pacific Ocean is warming and the consensus from computer models is for near average temperatures in the middle of the year. The SOI remains positive at approximately +3 for the 30 days ending 21 March. 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 24th April 2009