WA Seasonal Rainfall Outlook: probabilities for January to March 2005, issued 16th December 2004

Neutral odds for WA March quarter rainfall

The chances of accumulating at least average March quarter (Jan-Mar) rain are close to 50% over Western Australia, the Bureau of Meteorology announced today. So there are no strong swings in the odds towards wetter or drier conditions for the first three months of 2005.

probability of exceeding median rainfall - click on the map for a larger version of the map

For the January to March period in WA, the chances of above median rainfall are mainly between 45 and 50% (see map). So in years with ocean patterns like the current, about five seasons out of ten are expected to be wetter than average over Australia, with about five out of ten being drier.

This "neutral" outlook is due to the combined effect of above average temperatures in the Pacific Ocean and near-average temperatures in the Indian Ocean.

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).

Climate patterns across the Pacific continue to show some signs that are consistent with El Niño (eg warm central Pacific temperatures), and some that are not (eg wind and cloud patterns). The Southern Oscillation Index (SOI) dropped from –4 in October to –9 in November. The approximate SOI for the 30 days ending 13th December was –6.

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 El Niño 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 JANUARY 2005

Corresponding temperature outlook

November 2004 rainfall in historical perspective

September to November 2004 rainfall in historical perspective

 

Background Information