|WA Seasonal Rainfall Outlook: probabilities for April to June 2009, issued 24th March 2009|
Below average rainfall more likely in parts of northwest and central WA
The WA outlook for total June quarter rainfall (April-June), shows a drier than normal three months is more likely in parts of northwest and central WA, whilst for the remainder of the state the chances for above and below median rainfall are about equal.
The pattern of seasonal rainfall odds across Western Australia is mainly a result of warm conditions in the Indian Ocean in February; the Pacific Ocean had little contribution to this forecast.
For the April to June period, the chance of above median rainfall is below between 35 and 40% over parts of the Pilbara and Gascoyne in WA (see map). This means that for every ten years with ocean patterns like the current, about four years are expected to be wetter than average over this area, and six years are expected to be drier than average. For the rest of the state, the chance of exceeding the median rainfall during the June quarter is between 40 and 55%, meaning that above average falls are about as equally likely as below average falls.
New: Under the WATL part of the Bureau's website, there is an expanded set of seasonal rainfall outlook maps and tables, including the probabilities of seasonal rainfall exceeding given totals (e.g. 200 mm).
Outlook confidence is related to how consistently the Pacific and Indian Oceans affect Australian rainfall. During the June quarter, history shows this effect to be moderately consistent in a band from the Pilbara and northern Gascoyne to the Interior and Eucla. Elsewhere the effect is only weakly or very weakly consistent (see background information).
Pacific climate patterns were bordering on La Niña for several months, with above average wet season falls in the Australian tropics a direct result. The equatorial Pacific Ocean is warming and the consensus from computer models is for near average temperatures in the middle of the year. The SOI remains positive at approximately +3 for the 30 days ending 21 March. 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 detailed forecast maps, including the probabilities of seasonal rainfall exceeding given totals, can be found here.
|More information on this outlook is available from 8.30am to 4.30pm (WST) Monday to Friday by contacting the Climate Services Centre in the Bureau's Perth Office: (08) 9263 2222.|
THE NEXT ISSUE OF THE SEASONAL OUTLOOK IS EXPECTED BY 24th April 2009