|Northern Aust Seasonal Rainfall Outlook: probabilities for July to September 2008, issued 26th June 2008|
Neutral odds in outlook for northern Australia
The outlook for total rainfall over northern Australia for the September quarter shows mostly neutral odds for above or below average rainfall, with a moderate shift in the odds towards a relatively dry period over southwest Queensland.
The pattern of seasonal rainfall odds across Australia is a result of higher than average temperatures in the Indian Ocean surrounding the west coast of WA, and a warming trend in recent months over the equatorial Pacific.
The chances of exceeding the median rainfall over July to September are about 40% over the southwest of Queensland and close to 50% over the remainder of Queensland and the Northern Territory (see map). This means the chances of below normal falls are about 60% in the far southwest of Queensland.
So for every ten years with ocean patterns like the current, about six July to September periods are expected to be drier than average across southwest Queensland, while about four are wetter. Elsewhere, the chances of being wetter than normal are about the same as being drier than normal.
Outlook confidence is related to how consistently the Pacific and Indian Oceans affect Australian rainfall. During July to September, history shows this effect to be moderately consistent across most of Queensland and the NT (see background information).
The equatorial Pacific Ocean has been gradually warming during autumn and early winter resulting in the decay of the 2007/08 La Niña event, with neutral conditions currently prevailing. Computer models indicate a continuation of the warming trend, with neutral conditions the most likely outcome during the forecast period. The 30-day value of the Southern Oscillation Index (SOI) was zero as at 23rd June. 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 and the Northern Territory at the following numbers:
THE NEXT ISSUE OF THE SEASONAL OUTLOOK IS EXPECTED BY 25th July 2008