In the third week of April, sea surface temperatures remained below average in the central-eastern equatorial Pacific, and were even showing a slight sign of strengthening again, contrary to all predictions.
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This set-up is consistent with continued La Nina conditions, and therefore, at least a weak La Nina is likely to remain in place for a while yet.
A large majority of the international models on the Pacific expect SSTs to remain below normal at the level of a weak La Nina until at least the May to July quarter at this stage.
For the first time, at least one model has this pattern persisting into early spring and beyond.
IN OTHER NEWS:
A weak La Nina set up over winter does not necessarily bring conditions with widespread above average rainfall because moisture availability decreases with temperature.
However, it implies that at least average rains will be a feature in many parts of eastern and north eastern Australia over the winter months.
As noted last week, climate modelling coming from the United States now indicates around a 60 per cent chance the La Nina conditions will persist in the winter months (June to August) and go as far as indicating a 50-55pc chance of it persisting into the August to October quarter and this has not changed.
The unusual nature of this outlook can be clearly indicated when, historically it is noted that maximum strengths of La Nina events are normally confined to the months of October to February and on average last between seven and 10 months and rarely two years. We are going on for a third.
Although the Pacific Ocean patterns still dominate any prognoses, from May onwards the influence of the Indian Ocean increases.
The Indian Ocean Dipole, which has been neutral throughout the summer, is now showing signs of trending weakly negative.
Much of the tropical Indian Ocean has warmed in recent weeks, with SSTs now around 0.6 degrees warmer than average across the region and around the north west of continental Australia.
This has resulted in a forecast of negative IODs developing over winter.
A negative IOD increases the chances of above average winter-spring rainfall for much of Australia.
However, IOD assessments for a few months ahead have a lower level of confidence at this time.
There have been no recent changes in other climate indicators.
The Southern Annular Mode is fluctuating a little but remains mostly neutral and therefore it is having little effect at this stage, while the tropical Madden-Julian Oscillation remains weak although increased activity in the north Coral Sea has resulted in the most significant rain event of the season in north Queensland
