It says the key indicators for this forecast are a drop in the Southern Oscillation Index (SOI) to around -10, further warming of the Pacific and a strong decrease in the strength of the Trade Winds.

And the Bureau says many computer models remain firm in their predictions of an El Niño event in 2009.

This puts the odds of an El Niño at above 50 per cent, which is more than double the normal risk of an event.

However, the Bureau says it is still possible, though increasingly less likely, that the recent trends may stall without El Niño thresholds being reached.

El Niño events are usually (but not always) associated with below normal rainfall in the second half of the year across large parts of southern and inland eastern Australia.

Another adverse sign for southeastern Australian rainfall is the recent trend to positive values in the Indian Ocean Dipole (IOD), as measured by the Dipole Mode Index (DMI).