|National Seasonal Rainfall Outlook: probabilities for Spring 2005, issued 16th August 2005|
Drier spring for parts of southern Australia
There is an increased chance of a drier than average spring (September to November) in parts of southern Australia, the Bureau of Meteorology announced today. This includes some of the areas that have been suffering severe short-term rainfall deficiencies since the start of autumn, and longer-term deficiencies extending back more than a year. See the Drought Statement for more information. The chances of accumulating at least median spring rain are close to 50% across remaining parts of the country.
The pattern of seasonal rainfall odds is a result of continuing above average temperatures in both the Indian and tropical Pacific Oceans.
For the September to November period, the chances of above median rainfall are between 35 and 40% in a band extending from central South Australia through western Victoria and into the central north of Tasmania (see map). So in years with ocean patterns like the current, about four springs out of ten are expected to be wetter than median over these parts of southern Australia, with about six out of ten being drier. However, history shows only a weakly consistent influence from ocean temperatures on spring rainfall across a large part of this band, so this outlook should be applied with caution.
Outlook confidence is related to the influence of Pacific and Indian Ocean temperatures on seasonal rainfall. During spring, history shows this influence to be moderately consistent across most of the eastern mainland states and the NT, as well as northern Tasmania, southwest and far northwest WA, and parts of SA (see background information).
After reaching a positive value in June (+3), the Southern Oscillation Index (SOI) was steady in July with a value of +1. The approximate SOI for the 30 days ending 13th August was −6.
With the positive values of the SOI, recent cooling of the tropical Pacific and continued neutral cloud and wind patterns across the Pacific, the chances of an El Niño developing in 2005 are slim. For routine updates and comprehensive discussion on the latest data relating to El Niño, together with details on what the phenomenon is and how it has affected Australia in the past, 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.|
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 15th SEPTEMBER 2005