Seasonal Climate Outlook November - January 2007
The Bureau of Meteorology released the latest rainfall outlook on 25 October. The outlook for the November to January quarter indicates that the chances of exceeding the three-month median rainfall are between 45 and 60% across most of Victoria. However, the probabilities drop to around 40% along the State’s southwest coastal fringe.
Averaged over the November to January quarter, the chances for above-normal maximum temperatures over Victoria are between 60 and 70%.
The Bureau issued the latest ENSO Wrap-Up on 24 October. A La Niña event is in progress across the Pacific Basin. The main characteristics are colder than average temperatures along the equator, both on and below the surface, stronger than average Trade Winds and reduced cloudiness. Computer models indicate it will persist at least until the early part of 2008.
However, this La Niña is late to develop by historical standards. Widespread rainfall over Australia’s eastern half is not as likely to occur under late developing La Niña events. Indeed, it has been largely absent to date.
Australia’s climate has also been influenced by the unusually cool ocean temperatures to the north and northwest of the continent. These cooler than normal waters inhibit the formation of northwest cloud bands, which are the major source of winter and spring rain in central and south-eastern Australia during La Niña years. However, there has been a slight warming of the ocean to the north of the continent during October.