Seasonal Climate Outlook December 2006 - February 2007
The Seasonal Outlook released by the Bureau of Meteorology on 23 November 2006, for the December to February period, shows a neutral pattern of odds for exceeding the median rainfall over the summer period, with the chances of above median rainfall being 45-50% across most of Victoria.
Chances of exceeding median maximum temperatures are 55-60% across the State.
The current seasonal outlook is the result of higher than average temperatures in both the Pacific and Indian Oceans. The warm Pacific biases the climate towards drier than average conditions across eastern and northern Australia, but the warm Indian Ocean promotes wetter than average conditions across the tropics and in western WA. These two effects largely cancel each other out; hence the neutral odds.
The Southern Oscillation Index (SOI), negative for the sixth straight month, was -1.4 in November. There was a further strengthening of all El Niño indicators during November with the event about to enter the maturing phase. Computer models indicate that Pacific Ocean temperatures are likely to peak around January or February 2007. This timing would be consistent with the breakdown of past El Niño events.
In Australia, El Niño events are generally associated with a drier, warmer winter and spring period, followed by a switch to wetter conditions in January or February. However, this change is by no means guaranteed. Furthermore, El Niño events are associated with an increase in the number of extreme fire-risk days over southeastern Australia, that is, days where conditions are hot dry, and windy.