Weak events such as the current La Niña often present challenges to forecasting because they have the potential to fade or even occasionally strengthen a little unexpectedly.
This current event is favoured to remain weak at this stage and therefore it is also likely to be short lived.
Most international models indicate that it is unlikely to last beyond early autumn at the latest.
However, when it does fade away, a neutral pattern across the Pacific basin is likely to replace it and remain the dominant feature for at least another six months.
In other words, the chance of a new “El Nino” developing before the middle of spring at the earliest is low - there is only about 20 per cent (1 in 5) chance of this happening before October 2018.
So, a neutral pattern for long periods of next year means near average rainfall for many district with some bands of countryside in between becoming drier because they miss out on one or more of the occasional rain events.
These occasional rain events will also depend a little on what happens in the eastern Indian Ocean. Currently the Indian Ocean Dipole (IOD) is slightly positive (remember a positive IOD means potentially drier weather for SE Australia.).
A positive IOD is unusual with a La Niña operating in the Pacific and this is one of the reasons why conditions in NSW in coming months might be a little drier than would normally occur with a La Niña.
It must be stressed, however, that the IOD has minimal correlation with south-east Australian rainfall between now and the end of March, so what the IOD does in April and May will be more important.
In any case, the first six months of 2018 should end up with near normal rainfall and a continuation of above average temperatures with the greatest temperature departures from average occurring in February and March in the south and west of the state.
