Seasonal Climate Outlook - September 2011 to November 2011
The Bureau of Meteorology released its rainfall outlook for September to November 2011 on 25 August. The outlook reports that the odds favour a drier than normal season over the southern Murray-Darling Basin and most of Victoria. The outlook is based on the recent Pacific and Indian Ocean temperature patterns, and is a result of warm conditions in the Indian Ocean.
The Bureau’s latest ENSO Wrap-Up, issued on 17 August, reports that neutral ENSO conditions persist in the tropical Pacific Ocean, although Pacific Ocean temperatures have continued to cool over the past fortnight. The Southern Oscillation Index (SOI) remains slightly positive, and the trade winds are stronger than normal. Nevertheless, all indicators remain well short of the strong La Niña conditions recorded last year. The majority of international climate models forecast neutral conditions continuing into spring. No models are forecasting the development of El Niño conditions.
The influence of the Indian Ocean Dipole (IOD) on Australian rainfall is currently neutral. However, forecasts by the Bureau’s POAMA model suggest there remains a chance of a positive IOD event forming during late winter. Positive IOD events in the past have been associated with drier conditions over South-East Australia during the winter and spring months.