Seasonal Climate Outlook Message for March to June 2008

The bottom line

La Nina still in place

A mature La Nina event continues in the Pacific basin. This is expected to persist for at least 3 months. Although there is some warming in the eastern equatorial Pacific, the cool anomaly remains in the central Pacific.

As at 11 March the 30 day average of the SOI was plus 17.9.

The 30 day average of the SOI remained positive through February, and was plus 21.0 for the month. This is the highest averaged February SOI in the record. The SOI Phase for February was 'Consistently Positive' (Phase 2). The outlook for March to May shows a 50 to70 % chance of above median rainfall for much of Australia.

However, large regions of southeast Australia, particularly along the coast, only have a 30 to 50% chance of exceeding median rainfall. Further isolated southern coastal areas only have a 30 to 40 % chance of exceeding their median March to May rainfall. For more information try www.longpaddock.qld.gov.au http://www.longpaddock.qld.gov.au/>

Further analysis indicates rainfall for much Australia is more likely to be close to or above the long term average (or middle third to upper third) rather than below or well below average. The Bight coastal regions are more likely to be below average, rather than close to or above average.

The monsoon trough should re-establish across northern Australia with the next passage of the MJO (Phase 4) through the tropics. The MJO is currently in Phase 1 and should enter Phase 4 mid to late March. This will probably be the last MJO-induced monsoonal burst for summer 07-08.

During summer northern Australia can expect MJO enhanced rainfall probabilities Phases 4 through 7 during summer. We expect to see a greater impact from the MJO on our (northern Australian) rainfall during our summer and autumn.

The MJO often initiates the onset of the Australian monsoon, and is also associated increased rainfall for northern Australian. During summer the MJO is typically associated with Southern Hemisphere tropical storms, and cyclones in the Indian Ocean and western Pacific Ocean.

The MJO is a tropical band of low air pressure originating off the east coast of central Africa travelling eastward across the Indian Ocean and northern Australia roughly every 30 to 60 days. While the MJO is restricted to the tropics it affects areas well out of the tropics via teleconnections. This means that systems like the MJO interact with other weather and climate systems.

The MJO influences and is influenced by these other factors. Research has shown the MJO to be a useful indicator of the timing of potential rainfall events in Australia. For more information try www.apsru.gov.au/mjo/.