|Southeastern Aust Seasonal Rainfall Outlook: probabilities for Summer 2008/2009, issued 26th November 2008|
Wetter than normal summer indicated for northeast NSW
The outlook for total rainfall during summer (December to February) shows a moderate shift in the odds favouring wetter than normal conditions over northeastern NSW. However, over the remainder of southeastern Australia the outlook shows no strong bias towards either wetter or drier conditions, with the chances of being wetter than normal being about the same as the chances of being drier.
Over the far northeast of NSW, the chances of summer totals exceeding the 3-month median rainfall are around 60% (see map). This means for every ten years with ocean patterns like the current, about six years are expected to be wetter than average while about four years are expected to be drier. Over the remainder of southeastern Australia the chance of exceeding the seasonal median rainfall is between 40% and 60%. This means the chances of being wetter than normal in these areas are about the same as the chances of being drier.
The pattern of seasonal rainfall odds across southeastern Australia is mainly a result of recent warmer than average sea surface temperatures in the central and southeastern Indian Ocean, especially off the northwest Western Australian coast. Conditions in the Pacific Ocean have been neutral and so are currently not having a significant effect on the seasonal rainfall odds.
Outlook confidence is related to how consistently the Pacific and Indian Oceans affect Australian rainfall. During summer, history shows this effect to be moderately consistent over eastern NSW and most of southern Victoria. However, confidence is only weakly consistent over western NSW, northern Victoria, SA and most of Tasmania (see background information). In these areas where outlook confidence is not high caution should be used when interpreting these outlooks.
The tropical Pacific Ocean remains ENSO-neutral. Sea surface temperatures across most of the equatorial Pacific are near normal, although cool sub-surface temperatures persist in the eastern half of the basin. The SOI remains positive at approximately +14 for the 30 days ending 23 November. Computer models indicate that neutral conditions are likely to continue through summer. 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 17th December 2008