WA Seasonal Rainfall Outlook: probabilities for July to September 2003, issued 17th June 2003

Even odds for WA seasonal rainfall

The Bureau's latest seasonal rainfall outlook shows generally even odds for above average falls. The one exception is over part of north Queensland where above average falls are the more likely outcome.

For the July to September period across WA, the chances of above median rainfall are between 40 and 55% with no substantial swings towards a wetter or drier season (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, whilst about 5 out of 10 are drier.

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

It should also be noted that July to September is the heart of the dry season across northern parts of WA and heavy rain at that time of year is uncommon.

The Bureau's July to September rainfall outlooks have modest reliability in parts of southwestern WA, but mainly low reliability elsewhere in the State (see background information).

The Outlook probabilities are based on recent Indian and Pacific Ocean temperatures. The tropical Indian Ocean is warmer than average, whilst the Pacific has continued to cool following the end of the El Niño. For more detail see the El Niño Wrap-Up. The overall pattern of probabilities is almost entirely a result of warmer than average temperatures in the Indian Ocean.

May's value of the Southern Oscillation Index (SOI) was –7, two points below the April value of –5. The approximate SOI for the 30 days ending 14th June was –16.


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.


Archive of previous National Seasonal Rainfall Outlooks

Archive of previous National Seasonal Temperature Outlooks

May 2003 rainfall in historical perspective

March to May 2003 rainfall in historical perspective


Background Information