|National Seasonal Rainfall Outlook: probabilities for February to April 2008, issued 24th January 2008|
Wetter conditions favoured in southwest Australia
The national outlook for late summer to mid-autumn rainfall (February to April), shows a moderate to strong chance of exceeding the seasonal median in western WA. There are no strong swings towards below or above median rainfall over the rest of the country.
The pattern of seasonal rainfall odds across Australia is a result of cooler than average waters across the equatorial Pacific in association with La Niña, and continuing higher than average temperatures in the central to southeastern Indian Ocean.
The chances of exceeding the median rainfall over February to April are between 60 and 75% in southwest WA (see map). So for every ten years with ocean patterns like the current, about six or seven February to April periods are expected to be wetter than average in this part of the country, while about three or four are drier.
Over the rest of the country, the chances of exceeding the three-month median rainfall are between 40 and 60%. So the chances of being wetter than normal are about the same as the chances of being drier.
Outlook confidence is related to how consistently the Pacific and Indian Oceans affect Australian rainfall. During the February to April period, history shows the effect to be moderately consistent through the northern halves of both Queensland and the NT, most of WA, the far west of SA and southeast NSW. Elsewhere the effect is only weakly or very weakly consistent (see background information).
A La Niña event is in progress across the Pacific Basin and computer models indicate it will persist at least until autumn. The 30-day value of the Southern Oscillation Index (SOI) was +18 as at 21st January. 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, Brad Murphy on (03) 9669 4409.|
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 26th February 2008