Tas Seasonal Rainfall Outlook: probabilities for October to December 2004, issued 16th September 2004

Below average falls more likely over Tasmania

There is a moderate shift in the odds towards below average rainfall for the December quarter over Tasmania, particularly in the north of the State, the Bureau of Meteorology announced today.

Over Tasmania, the chances of above median rainfall for the December quarter are generally close to 40%, being marginally less than this in parts of the north, and somewhat higher than this in remaining areas. So in years with ocean patterns like the current, about six October to December periods out of ten are expected to be drier than average across the State, with about four out of ten being wetter.

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

The current pattern of outlook probabilities is due to recent temperature patterns in both the Pacific and Indian Oceans.

Outlook confidence is related to the influence of Pacific and Indian Ocean temperatures on seasonal rainfall. During the December quarter, history shows this influence to be moderately consistent over northwest and central Tasmania, but weakly consistent in the east and southwest (see background information).

The chance of a late-developing El Niño event increased over the past month, with several but not all indicators reaching their El Ni˜o thresholds. The mounting evidence includes warming of the central Pacific, reduced Trade Winds in the same area and continued negative values of the Southern Oscillation Index (SOI) which came in at –8 for August. The approximate SOI for the 30 days ending 13th September 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 (EST) Monday to Friday by contacting the Climate and Consultancy section in the Bureau's Hobart Office: (03) 6221 2043.


Corresponding temperature outlook

August 2004 rainfall in historical perspective

June to August 2004 rainfall in historical perspective


Background Information