|National Seasonal Rainfall Outlook: probabilities for Winter 2008, issued 27th May 2008|
Mixed rainfall odds for winter
The national outlook for total rainfall over winter, shows a shift in the odds towards wetter conditions over much of Queensland and northeast NSW. In contrast, drier conditions are predicted for southwest WA.
The pattern of seasonal rainfall odds across Australia is a result of higher than average temperatures in the Indian Ocean, and cooler than average waters in the central to western equatorial Pacific in association with the decaying La Niña pattern.
The chances of exceeding the median rainfall over winter are between 60 and 70% over much of Queensland, and northeastern parts of NSW (see map). So for every ten years with ocean patterns like the current, about six or seven winter periods are expected to be wetter than average in these parts of northeastern Australia, while about three or four are drier, it should be noted, however, that this is a seasonally drier time of year in some northern parts of the country.
In contrast, the southwest corner of WA has an increased chance of drier than average conditions with only a 30 to 40% chance of exceeding the median rainfall for the season. However, users are advised to use caution in applying these probabilities because the confidence in the outlook is generally low in southwest WA for winter.
Over the rest of the country, the chances of exceeding the three- month median rainfall are mainly between 45 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 winter, history shows this influence to be moderately consistent across much of Queensland, the NT, NSW and Victoria, but generally weakly consistent elsewhere across the country, reaching moderate only in patches (see background information).
The 2007/08 La Niña event in the Pacific Basin has decayed to neutral conditions: computer models indicate a continuation of neutral conditions through the forecast period. The 30-day value of the Southern Oscillation Index (SOI) was −3 as at 24th May. 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: Lyn Bettio on (03) 9669 4165, David Jones on (03) 9669 4085, Grant Beard on (03) 9669 4527.|
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 June 2008