|National Seasonal Rainfall Outlook: probabilities for November 2007 to January 2008, issued 25th October 2007|
Increased falls for parts of northern & eastern Australia
The national outlook for total rainfall over the late spring to mid-summer period (November to January), shows a moderate to strong shift in the odds favouring above average falls from the NT and northern WA to southern Queensland and northern NSW. A wetter season is also favoured in southwest WA, although it's generally a dry time of year in this part of the country.
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.
The chances of exceeding the median rainfall for the November to January period are between 60 and 70% in a broad region stretching from northern WA and the NT across western and southern Queensland and the northern half of New South Wales (see map). In parts of the northern NT and far northeast of WA, the chances approach 75%. There are also 60 to 70% chances in southwest WA.
So for every ten years with ocean patterns like the current, about six or seven November to January periods are expected to be wetter than average in these parts of the country, while about three or four are drier.
Over most remaining parts of the country, the chances of exceeding the three-month median rainfall are between 45 and 60%, except in southwest Victoria where the probabilities drop to around 40% along the coastal fringe.
Outlook confidence is related to how consistently the Pacific and Indian Oceans affect Australian rainfall. During the November to January period, history shows this effect to be moderately consistent across much of Tasmania, NSW, Queensland and the NT, but generally weakly consistent elsewhere (see background information).
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 +1 as at 22nd October. 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.
|The following climate meteorologists in the National Climate Centre can be contacted about this outlook: Grant Beard on (03) 9669 4527, Lyn Bettio on (03) 9669 4165, Blair Trewin on (03) 9669 4623.|
Regional commentary is available from the Climate Services Sections in the Bureau's Regional Offices:
THE NEXT ISSUE OF THE SEASONAL OUTLOOK IS EXPECTED BY 27th NOVEMBER 2007