|National Seasonal Rainfall Outlook: probabilities for May to July 2008, issued 23rd April 2008|
Higher seasonal rainfall favoured in parts of north & east Australia
The national outlook for total rainfall over the late autumn to mid-winter period (May to July), shows a moderate shift in the odds favouring a wetter than normal season in a broad band from northern WA and the NT through to southern Queensland and northern NSW.
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 across the equatorial Pacific in association with La Niña.
The chances of exceeding the median rainfall over May to July are between 60 and 70% in a broad band covering far northern WA, most of the NT, northwest and southern Queensland, and the far north of NSW (see map). It should be noted, however, that this is a seasonally dry time of year over some northern parts of Australia. So for every ten years with ocean patterns like the current, about six or seven May to July periods are expected to be wetter than average in these parts of eastern and northern Australia, while about three or four are drier.
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 the May-July period, history shows this effect to be moderately consistent in a band from the central Northern Territory across most of the southern two-thirds of Queensland, as well as the north-eastern half of New South Wales. Moderate consistency is also evident in much of Tasmania, parts of southern Victoria, and patches through the interior of Western Australia. Elsewhere the effect is only weakly or very weakly consistent (see background information).
The La Niña event in the Pacific Basin is weakening: computer models indicate a return to neutral conditions over the outlook period of May-July. The 30-day value of the Southern Oscillation Index (SOI) was +5 as at 20th April. 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, David Jones on (03) 9669 4085.|
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 May 2008