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Seasonal Climate Outlook - November 2010 to January 2011

The Bureau of Meteorology released its rainfall outlook for November 2010 to January 2011 on 26 October. The outlook for south-eastern Australia favours wetter than average conditions for November to January. The chances of exceeding median rainfall during those months across northern Victoria are between 60 and 65%. However the odds for southern Victoria are closer to neutral (around 55%), with above average rainfall being as likely as below average rainfall.

This is consistent with the indicators outlined in the Bureau’s latest ENSO Wrap-Up, issued on 27 October. The Bureau reports that a moderate/strong La Niña remains in the Pacific Ocean. Based on the current strength of the event and long range model outlooks, the La Niña is expected to persist into early 2011.

All ENSO indicators remain firmly at La Niña levels, despite the brief impact of a Madden Julian Oscillation event in mid-October. The tropical Pacific Ocean is significantly cooler than the long-term average for this time of year, both at and below the surface. The Southern Oscillation Index (SOI) remains strongly positive at +21, trade winds are stronger than average and cloudiness over the central tropical Pacific remains suppressed,

The negative Indian Ocean Dipole (IOD) event also continues in the Indian Ocean. The combination of a negative IOD event and a La Niña event is often associated with above average rainfall over south-eastern Australia in spring. Experimental forecasts by the Bureau’s POAMA model also favour a wetter spring. Negative IOD events typically decay during November-December, with the onset of the northern wet season. A recent rise in the IOD index and southwards movement of the monsoon trough indicate the negative IOD event may already be weakening.

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