|National Seasonal Rainfall Outlook: probabilities for April to June 2008, issued 28th March 2008|
Higher June quarter rainfall favoured in eastern Australia
The national outlook for total rainfall over the June quarter (April to June), shows a moderate to strong shift in the odds favouring a wetter than normal season over the eastern halves of Queensland and NSW.
The pattern of seasonal rainfall odds across Australia is a result of continuing higher than average temperatures in the southeastern Indian Ocean, and cooler than average waters across the equatorial Pacific in association with La Niña.
The chances of exceeding the median rainfall over April to June are between 60 and 70% over most of the eastern halves of Queensland and NSW, approaching 75% in a region straddling the border (see map). So for every ten years with ocean patterns like the current, about six or seven June quarters are expected to be wetter than average in these parts of eastern Australia, while about three or four are drier.
Over the rest of the country, the chances of exceeding the three-month median rainfall are mainly between 45 and 60%. So the chances of being wetter than normal are about the same as the chances of being drier.
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).
The La Niña event in the Pacific Basin is showing signs of weakening, although computer models indicate it is likely to persist until about the end of autumn. The 30-day value of the Southern Oscillation Index (SOI) was +15 as at 25th 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.
|The following climate meteorologists in the National Climate Centre can be contacted about this outlook: Grant Beard on (03) 9669 4527, Lyn Bettio on (03) 9669 4165, David Jones on (03) 9669 4085.|
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 April 2008