Seasonal Climate Outlook April - June 2007
The latest Seasonal Forecast issued by the Bureau of Meteorology on 26 March continues to indicate near neutral odds for rainfall over April to June across the State with the chances of receiving above median rainfall being 44-55%.
Likewise, the chances of a warmer than average season are also close to 50:50 across the State.
The 2006/07 El Nino event has ended. Central to eastern Pacific temperatures cooled rapidly during January and February but have remained close to average during March. The SOI (which increased to -1.7 in March), trade winds, and Pacific cloud patterns (which are other ENSO indicators) are also currently in a neutral phase.
There appears little chance of a return to El Nino conditions in 2007, with a continuation of neutral, or a switch to La Nina, conditions considered to be the more likely outcome.
Many computer models predict further cooling of the Pacific during the first half of 2007, with all predicting a continuation of neutral, or the development of La Nina, conditions.
The chance of a La Nina event developing in 2007 is thought to be higher than the long-term average because:
- they have a tendency to follow an El Nino,
- the 2006/07 El Nino decayed earlier than normal, thereby giving time for a La Nina to begin developing during the critical March to June period,
- a large pool of cold sub-surface water remains in the central to eastern tropical Pacific Ocean and is starting to affect surface temperatures in the region.
The Bureau’s next seasonal outlook is expected on 23 April 2007.