|National Seasonal Rainfall Outlook: probabilities for August to October 2006, issued 25th July 2006|
Decreased seasonal falls more likely in northeastern Australia
There is a moderate to strong shift in the odds towards below normal seasonal rainfall across northeastern Australia, the Bureau of Meteorology announced today. Across the rest of the country, the chances are generally close to 50% for accumulating at least median rainfall over August to October.
The pattern of seasonal rainfall odds across Australia is partly a function of raised temperatures in the Pacific, but more strongly related to rapidly increasing Indian Ocean temperatures.
For the August to October period, the chances of above median rainfall are below 40% north of a line that connects the SA/NSW/QLD border region with Rockhampton in Queensland, and with Daly Waters in the NT (see map). In the Northern Goldfields district in Queensland, the chances drop to about 20%. These probabilities mean that below median falls have a 60 to 80% chance of occurring in these regions.
So in years with ocean patterns like the current, about six to eight August to October periods out of 10 are expected to be drier than average in northeast Australia, with about two to four out of ten being wetter. However, it should be remembered that it in terms of average conditions, it is a rather dry time of year in northeastern Australia, with heavy rain being uncommon.
Outlook confidence is related to how consistently the Pacific and Indian Oceans affect Australian rainfall. During August to October, history shows this effect to be moderately consistent across most of Queensland, the east and north of the NT and the northern inland of NSW. Elsewhere, it is generally weakly consistent, reaching moderate only in patches, including northern Tasmania (see background information).
After falling to −10 in May, the Southern Oscillation Index (SOI) rose slightly in June to a value of −6. The approximate SOI for the 30 days ending 22nd July was −9.
Although the chances of an El Niño have risen somewhat in the past month, continued neutral ENSO conditions is the most likely outcome for the remainder of 2006. For routine updates and comprehensive discussion on the latest data relating to ENSO, together with details on what the phenomenon is and how it has affected Australia in the past, 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.
|The following climate meteorologists in the National Climate Centre can be contacted about this outlook: Grant Beard on (03) 9669 4527, Andrew Watkins on (03) 9669 4360, Lynette Bettio on (03) 9669 4165.|
Regional commentary is available from the Climate and Consultancy Sections in the Bureau's Regional Offices:
THE NEXT ISSUE OF THE SEASONAL OUTLOOK IS EXPECTED BY 24th AUGUST 2006