|WA Seasonal Rainfall Outlook: probabilities for Spring 2008, issued 26th August 2008|
Above average rainfall favoured in southwest WA
The Western Australia outlook for total spring (September to November) rainfall shows that a wetter than normal spring is more likely in southwest WA, whilst the odds are neutral for the remainder of the State.
The pattern of seasonal rainfall odds across Western Australia is mainly a result of continued warmth in the central and southeastern Indian Ocean, especially off the west coast of WA.
The chances of exceeding the median rainfall for spring are between 60 and 75% over southwest WA, grading to between 40 and 60% through the remainder of the state (see map). So for every ten years with ocean patterns like current, about six or seven springs are expected to be wetter than average in southwest WA, while about three or four are drier. For the remainder of the state the odds of being wetter than normal are almost the same as the odds of being drier.
Outlook confidence is related to how consistently the Pacific and Indian Oceans affect Australian rainfall. During spring, history shows this effect to be moderately consistent in parts of the southwest and far north, but only weakly consistent through central parts of WA (see background information).
The approximate 30-day value of the Southern Oscillation Index (SOI) was +3 as at 23 August, while a mixed pattern of warmer and cooler than normal temperatures persists along the equatorial Pacific Ocean. Both these observations indicate a neutral climate pattern across the Pacific, which computer models indicate is likely to continue for the next few seasons. 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 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 25th September 2008