|WA Seasonal Rainfall Outlook: probabilities for November 2005 to January 2006, issued 18th October 2005|
Above average seasonal falls a 50:50 prospect
The chances of accumulating at least median rain during the late spring to mid-summer period (Nov-Jan) are close to 50% across Western Australia, the Bureau of Meteorology announced today. 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.
For the November to January period, the chances of above median rainfall are mostly between 50 and 55% over WA, reaching a little above 55% in parts of the Kimberley (see map).
So in years with ocean patterns like the current, about five November to January periods out of ten are expected to be wetter than the median over Western Australia, 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 the November to January quarter, history shows this influence to be moderately consistent in the far north of WA, but generally weakly consistent elsewhere in the State (see background information).
The Southern Oscillation Index (SOI) has fluctuated about zero during recent months with values of +1 in July, −7 in August and +4 in September. The approximate SOI for the 30 days ending 15th October was +4.
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 16th NOVEMBER 2005