|National Seasonal Rainfall Outlook: probabilities for Winter 2009, issued 26th May 2009|
No strong shifts in winter rainfall odds
The national outlook for total rainfall over winter (June to August), shows no strong shifts in the odds favouring either wetter or drier conditions. In other words the chances of above normal falls are about the same as the chances of below normal.
The exceptions are in a few small patches in the south within which there are moderate shifts in the odds favouring a drier than average season.
The pattern of seasonal rainfall odds across Australia is a result of recent warm conditions in the Indian Ocean and an increasing level of warmth in the Pacific. The influences from these two oceans counteract each other in eastern Queensland and northern NSW: the Indian Ocean pattern promotes wetter conditions while the Pacific biases the climate towards a drier than normal season.
For the June to August period, the chance of exceeding median rainfall is between 40 and 55% in most parts of the country (see map). This means that for every ten years with ocean patterns like the current, about four or five years are expected to be wetter than average during winter, while about five or six years are expected to be drier.
In a few small patches in WA, SA and Victoria, the chances of a wetter than normal winter drop below 40% indicating an increased risk of dry conditions.
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 winter, history shows this influence to be moderately consistent across much of Queensland, the NT, NSW and Victoria, but generally weakly consistent elsewhere across the country, reaching moderate only in patches (see background information).
Recent trends in Pacific climate patterns and the latest outputs from computer models indicate an increased risk of an El Niño developing during winter and spring. The SOI is approximately −11 for the 30 days ending 23 May. 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 23rd June 2009