|Northern Aust Seasonal Rainfall Outlook: probabilities for Summer 2007/2008, issued 22nd November 2007|
Increased summer rainfall for southeast Queensland
The northern Australian outlook for total rainfall during the heart of the wet season (December to February), shows a moderate shift in the odds favouring above average totals in southeast Queensland. Over the rest of the NT and Queensland, the chance of receiving above average rainfall is about equal to the chance of receiving below average rainfall.
The pattern of seasonal rainfall odds across Australia is mainly a result of continuing higher than average temperatures over parts of the tropical and sub-tropical Indian Ocean. However, cooler than average temperatures in the equatorial central to eastern Pacific have contributed to the higher chances of a wetter than average summer in eastern Australia.
The chances of exceeding the median rainfall for summer are between 60 and 70% in an area of southeast Queensland roughly bounded by Gladstone, Charleville and Godooga (NSW) (see map). So for every ten years with ocean patterns like the current, about six or seven summers are expected to be wetter than average in southeast Queensland, while about three or four are drier.
Outlook confidence is related to how consistently the Pacific and Indian Oceans affect Australian rainfall. During December to February, history shows this effect to be moderately consistent in parts of eastern and southern Queensland and the far northwest of the NT (see background information). Elsewhere in Queensland and the NT the effect is generally only weakly or very weakly consistent, and this is the reason for the chances being close to 50%.
A late-developing La Niña event is in progress across the Pacific Basin and computer models indicate it will persist at least until the early part of 2008. The 30-day value of the Southern Oscillation Index (SOI) was +11 as at 19th November. 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 17th DECEMBER 2007