|WA Seasonal Rainfall Outlook: probabilities for Summer 2005/2006, issued 16th November 2005|
50:50 chances for a wetter than average summer
The chances of accumulating at least median rainfall during summer (Dec-Feb) are close to 50% across the entire state of Western Australia, the Bureau of Meteorology announced today (see map). The outlooks are based on relationships between Pacific and Indian Ocean temperatures and Australian rainfall. Recent ocean temperatures have not been sufficiently warmer or cooler than average to produce a strong bias in rainfall outlook odds.
So in years with ocean patterns like the current, about five summers out of ten are expected to be wetter than the median over WA, with about five out of ten being drier.
Outlook confidence is related to the influence of Pacific and Indian Ocean temperatures on seasonal rainfall. During summer, history shows this influence to be moderately consistent across much of WA (see background information).
The Southern Oscillation Index (SOI) has risen steadily over the past few months with values of −7 in August, +4 in September and +11 in October. The approximate SOI for the 30 days ending 13th November was +8.
For routine updates on the latest data relating to El Niño, together with details on what the phenomenon is and how it has affected Australia in the past, 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 information on this outlook is available from 9.00am to 5.00pm (WST) Monday to Friday by contacting the Climate and Consultancy section in the Bureau's Perth Office: (08) 9263 2222.|
THE NEXT ISSUE OF THE SEASONAL OUTLOOK IS EXPECTED BY 19th DECEMBER 2005