|WA Seasonal Rainfall Outlook: probabilities for October to December 2005, issued 15th September 2005|
Above average falls more likely in parts of WA
There is a moderate shift in the odds towards above average rainfall for the December quarter (October to December) in a region extending from northwest to central WA, the Bureau of Meteorology announced today. However, the chances of accumulating at least median three-month rainfall are close to 50% across the rest of the State.
For the October to December period, the chances of above median rainfall are between 60 and 65% in an area extending south from Port Hedland across much of the Pilbara and Gascoyne districts as well as parts of the Goldfields and Interior districts (see map). It should be noted though, that the December quarter is a seasonally dry time of year in the Fortescue and West Gascoyne with heavy rain being uncommon.
So in years with ocean patterns like the current, about six December quarters out of ten are expected to be wetter than the median over these parts of Western Australia, with about four out of ten being drier.
Outlook confidence is related to the influence of Pacific and Indian Ocean temperatures on seasonal rainfall. During the December quarter, history shows this influence to be moderately consistent across much of WA (see background information).
The Southern Oscillation Index (SOI) fell from +1 in July to −7 in August. However, the SOI has begun to rise again with the approximate value for the 30 days ending 12th September being −1.
With all the main tropical Pacific climate indicators remaining neutral, an El Niño event developing in 2005 is not considered a realistic possibility. For routine updates and comprehensive discussion 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 18th OCTOBER 2005