|Southeastern Aust Seasonal Rainfall Outlook: probabilities for August to October 2008, issued 25th July 2008|
Neutral conditions indicated for much of southeastern Australia
The outlook for southeastern Australia for total August to October rainfall shows generally neutral conditions for much of southeastern Australia but moderate swings in the odds towards below-normal rainfall in an area covering eastern South Australia and far western NSW.
The pattern of seasonal rainfall odds across southeastern Australia is a result of a continued strong warming trend in the central and southeastern Indian Ocean, off the west coast of Western Australia, and a warming trend in recent months over the equatorial Pacific.
The chances of exceeding the median rainfall over the August to October period are between 30 and 40% over far western NSW and much of central and eastern South Australia (see map). This means the chances of below average rainfall are between 60 and 70% in these areas.
So in years with ocean patterns like the current, about six to seven August to October periods out of ten are expected to be drier than average in these parts of southeastern Australia, while three to four are wetter. However, confidence is not high through much of South Australia at this time of year so the outlook needs to be used with caution in this region.
Over the rest of southeastern Australia, August to October rainfall totals have a 40 to 50% chance of exceeding the three-month median: 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 August to October, history shows this effect to be moderately consistent over the northern inland of NSW. Elsewhere, it is generally weakly consistent, reaching moderate only in patches, including central Victoria and NE Tasmania (see background information).
The 30-day value of the Southern Oscillation Index (SOI) was +3 as at 22 July. Computer models indicate a continuation of neutral conditions across the equatorial Pacific Ocean as the most likely outcome during the forecast period. 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 27th August 2008