|Northern Aust Seasonal Rainfall Outlook: probabilities for Autumn 2009, issued 20th February 2009|
Wetter than normal autumn favoured for northern Queensland
The outlook for total autumn rainfall shows a shift in the odds favouring higher than normal rainfall over much of northern Queensland.
The pattern of seasonal rainfall odds is mainly a result of a return to warm conditions in the Indian Ocean in January, after an anomalous cooling trend in the later part of 2008.
The chance of exceeding median rainfall over much of northern Queensland during the March to May quarter is between 60 and 70%. This means that for every ten years with ocean patterns like the current, about six or seven years are expected to be wetter than average in this region, while about three or four years are expected to be drier.
Across the remainder of the region, the chance of exceeding the median rainfall during autumn is between 45 and 60%, meaning that above average falls are about as equally likely as below average falls.
Outlook confidence is related to how consistently the Pacific and Indian Oceans affect Australian rainfall. During autumn, history shows the effect to be moderately consistent across much of the region, though is only weakly or very weakly consistent in southern parts of the Northern Territory and Queensland (see background information).
Some warming of the equatorial Pacific Ocean occurred in January, following cooling in December, so that sea surface temperatures (SST) in the central Pacific have now eased back to neutral values. While sub-surface waters are cool in the eastern Pacific, those in the west of the basin are warmer than normal and there are indications that these will impact on the surface in coming months. Furthermore, most current model outlooks suggest further warming in the Pacific. The most likely scenario is for conditions to remain neutral. The SOI remains positive at approximately +15 for the 30 days ending 17 February. 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 detailed forecast maps, including the probabilities of seasonal rainfall exceeding given totals, can be found here.
More information on this outlook is available by contacting the Bureau's Climate Services sections in Queensland and the Northern Territory at the following numbers:
THE NEXT ISSUE OF THE SEASONAL OUTLOOK IS EXPECTED BY 24th March 2009