Seasonal Climate Outlook May - July 2007
The latest Seasonal Outlook issued by the Bureau of Meteorology on 23 April continues to indicate near neutral odds for rainfall over May to July, with the chances of Victoria receiving above median rainfall being 50-55%.
The chances of a warmer than average season have dropped to 35-40% across most of the State, increasing to 40-45% in the north and far east.
Conditions in the equatorial Pacific Ocean continue to display the precursors required for the development of a La Nina event during 2007. A large body of cool subsurface water persists in the eastern Pacific, and some cooler than normal surface water has also emerged in a narrow equatorial strip in the eastern Pacific. Furthermore, trade winds remain enhanced near the dateline, and convection (high cloud) has continued to be reduced in the east and slightly enhanced in the west.
The SOI for April was -3.0 compared with -1.4 in March, but can vary significantly during the Austral autumn, and a drop is not necessarily an indicator of the longer-term climatic situation.
All major international computer models show further cooling of the equatorial Pacific Ocean over the coming months.
Indications therefore are that there is an elevated chance of a La Niña event occurring during 2007. Historically, La Niña events bring wetter than normal conditions across much of the eastern half of Australia from autumn onwards.
The Bureau’s next seasonal outlook is expected on 24 May 2007.