|Southeastern Aust Seasonal Rainfall Outlook: probabilities for April to June 2008, issued 28th March 2008|
Higher June quarter rainfall favoured in eastern NSW
For southeastern Australia, the 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 half of NSW.
The pattern of seasonal rainfall odds across southeastern Australia is mostly a result of 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 half of NSW, approaching 75% in some of the northern inland (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 southeastern Australia, while about three or four are drier.
Over the rest of the southeast, the chances of exceeding the three-month median rainfall are 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 over most of both SA and Victoria, the far southwest of NSW, northeast NSW and eastern Tasmania. In a band running between the northwest and southeast corners of NSW, 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.
More information on this outlook is available Monday to Friday from 9.00am to 5.00pm local time by contacting the Bureau's Climate Services sections in Queensland, NSW, SA, Victoria and Tasmania at the following numbers:
THE NEXT ISSUE OF THE SEASONAL OUTLOOK IS EXPECTED BY 23rd April 2008