Seasonal Climate Outlook November 2006 - January 2007
The Seasonal Outlook released by the Bureau of Meteorology on 26 October 2006, for the November to January period, shows the chances of above median rainfall are 40-45% across the north of Victoria, increasing to 45-50% in the south.
Chances of exceeding median maximum temperatures are 60-65% across the State.
There was a general strengthening of all El Niño indicators during October, with the event primed to enter the maturing phase. The Southern Oscillation Index (SOI), negative for the fifth straight month, dropped from -5.1 in September to -15.3 in October. In addition to the negative SOI, the equatorial Pacific has been warming and the Trade Winds have been weak.
The observed below average rainfall since late autumn across Australia's southern half, especially in the southeast and southwest, is also consistent with a developing El Niño event. Computer models indicate that Pacific Ocean temperatures are likely to peak around January or February 2007.
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.
Even if El Niño thresholds are not maintained across the range of indicators, a warming Pacific and a low SOI bias the climate towards being drier and warmer than average across eastern Australia for the remainder of 2006. This is reflected in the latest outlook.