NSW Seasonal Rainfall Outlook: probabilities for July to September 2004, issued 17th June 2004

Neutral outlook for NSW September quarter rainfall

There is a moderate shift in the odds towards above average three-month falls in north Queensland and small parts of southwest WA, the Bureau of Meteorology announced today. However, for most of the country, including all of NSW, the shifts in the odds are too weak to offer any firm guidance as to the most likely outcome for September quarter rainfall.

However, even near average rainfall in the southeast of the country during the coming three months, will only raise the year-to-date total to somewhere near the tenth percentile. In other words, 90% of years would still be wetter.

The current pattern of outlook probabilities has been mostly influenced by recent temperature patterns in the Pacific Ocean.

For the July to September period in NSW, the chances of above median rainfall are mainly between 50 and 55% (see map). So in years with ocean patterns like the current, about five September quarters out of ten are expected to be wetter than average over the State, with about five out of ten being drier.

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

Outlook confidence is related to the influence of Pacific and Indian Ocean temperatures on seasonal rainfall. During July to September, history shows this influence to be moderately consistent across large parts of NSW (see background information).

Both the Indian and tropical Pacific Oceans remain mostly warmer than average, although both cooled between April and May. For more detail see the the El Niño Wrap-Up.

The Southern Oscillation Index (SOI) rebounded strongly in May to a value of +13, 28 points above April's –15. The approximate SOI for the 30 days ending 14th June was +7.

 

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 (EDT) Monday to Friday by contacting the Climate and Consultancy section in the Bureau's Sydney Office: (02) 9296 1522.
 

THE NEXT ISSUE OF THE SEASONAL OUTLOOK IS EXPECTED BY 13th JULY 2004.

Corresponding temperature outlook

May 2004 rainfall in historical perspective

March to May 2004 rainfall in historical perspective

 

Background Information