|WA Seasonal Rainfall Outlook: probabilities for January to March 2004, issued 16th December 2003|
Neutral odds for March quarter rainfall over WA
The Bureau's seasonal rainfall outlook for the March quarter shows no strong swings in the odds towards wetter or drier conditions over WA. The chances of above average seasonal falls are generally close to a neutral 50%. This outlook is due to the fact that Pacific and Indian Ocean temperatures don't strongly influence Australian rainfall during mid-summer to early autumn.
For the January to March period, the chances of above median rainfall are between 50 and 55% across Western Australia (see map). So with climate patterns like the current, about 5 seasons out of 10 are expected to be wetter than average over the State, with about 5 out of 10 being drier.
Outlook confidence is related to the influence of Pacific and Indian Ocean temperatures on seasonal rainfall. During the March quarter, history shows this influence to be moderately consistent southwest of a line from Exmouth to Eucla, and in parts of far eastern WA. Elsewhere the influence is only weakly consistent (see background information).
Following a recent cooling trend, the tropical Indian Ocean warmed slightly during November, as did the tropical Pacific. For more detail see the El Niño Wrap-Up. The temperature patterns in the Indian Ocean and Pacific Oceans are not extreme enough to produce large swings in the outlook probabilities.
November's value of the Southern Oscillation Index (SOI) was 3, slightly below the 2 recorded in October. The approximate SOI for the 30 days ending 14th December was +1.
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 15th JANUARY 2004.