|WA Seasonal Rainfall Outlook: probabilities for May to July 2007, issued 23rd April 2007|
Above-normal seasonal rainfall favoured in SE Qld & northeast NSW
The national outlook for total May to July rainfall, shows a moderate swing in the odds towards above-normal rainfall in a relatively small region spanning parts of southeast Queensland and northeast New South Wales. However, over most of the country the chances of accumulating at least average rain for the coming three months are close to 50%.
The pattern of seasonal rainfall odds across Australia is a result of recent higher than average temperatures in the equatorial Pacific Ocean and also in parts of the tropical and sub-tropical Indian Ocean. Most influence has come from the Indian.
The chances of exceeding the median rainfall for the May to July period are between 60 and 65% in an area straddling the NSW/Qld border roughly between Armidale (NSW) and Roma (Qld) (see map). So in years with ocean patterns like the current, about six May to July periods out of ten are wetter than average and four out of ten are drier in this region.
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 north-eastern half of New South Wales. 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).
The Southern Oscillation Index (SOI) remained neutral in March with a value of −1 following the −3 in February. The approximate 30-day value as at 18th April was −12.
A large body of cool subsurface water persists in the central to eastern Pacific, thereby raising the potential for a La Niña to develop in 2007. Furthermore, some cooler than normal surface water has emerged in a narrow equatorial strip in the eastern Pacific. 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 information on this outlook is available from 9.00am to 5.00pm (WST) Monday to Friday by contacting the Climate and Consultancy section in the Bureau's Perth Office: (08) 9263 2222.|
THE NEXT ISSUE OF THE SEASONAL OUTLOOK IS EXPECTED BY 24th MAY 2007