WA Seasonal Rainfall Outlook: probabilities for February to April 2005, issued 18th January 2005

Above average falls more likely in parts of western WA

There is a moderate shift in the odds towards above average rainfall for the late summer to mid-autumn quarter (Feb-Apr) in parts of western WA, the Bureau of Meteorology announced today. But for most of the State, the chances of accumulating at least average rain between February and April are close to 50%.

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

For the February to April period, the chances of above median rainfall are between 60 and 65% in the area near and to the northwest of Meekatharra (see map). So in years with ocean patterns like the current, about six out of ten are expected to be wetter than average in this part of the State, with about four out of ten being drier. This outlook pattern is due to the combined effects of above average temperatures in the tropical Pacific Ocean, and slightly warmer than average conditions in the Indian Ocean.

Outlook confidence is related to the influence of Pacific and Indian Ocean temperatures on seasonal rainfall. During the February to April period, history shows this influence to be moderately consistent through most of WA (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) was –8 in December following –9 in November. The approximate SOI for the 30 days ending 15th January was –3.

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.


Corresponding temperature outlook

December 2004 rainfall in historical perspective

October to December 2004 rainfall in historical perspective


Background Information