The Outlook | Neutral pattern by autumn

There could be a neutral weather pattern by autumn


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About 70 per cent of models now believe a weak El Nino will be established by the end of November and it looks likely that it will only persist for a few months.

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THE occasional rain event continues to relieve the drought conditions in parts of the state but - despite a few hiccups – the progress towards at least a weak El Nino in the Pacific basin before the end of the year appears to be on track.

About 70 per cent of models now believe a weak El Nino will be established by the end of November and it looks likely that it will only persist for a few months.

Hot air has continued to build over the “heat engine” areas of northern and north-western Australia and above average temperatures have returned to the south-eastern states. 

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These are expected to persist through summer and early autumn at least. 

Rainfall might not be greater effected. 

About 30 per cent of El Nino events do not have a major effect on rainfall, (70pc reduce the chance of rain) but even if this event turns out to be one of those 30pc, any occasional rainfall event is unlikely to be sufficient to overcome the moisture deficiencies already established by over a year of drought.

As noted previously, severe storm activity is often more prevalent in these weak but developing situations, but this is more likely over Queensland and north-eastern NSW. 

Such activity is favoured to locally boost rainfall and that gives a bit of support to the prognosis of minimal effect from the developing El Nino. Another factor worth considering is sea surface temperature (SST) patterns. 

In a normal El Nino event, SSTs are lower than normal in the western tropical Pacific. 

Around Australia at the moment, SSTs are mostly close to average, although some areas near the coast of southeast Australia has warmed significantly over the past two weeks and is currently much warmer than average. 

Such an occurrence can encourage rainfall at least in eastern NSW. 

In the longer term, there is an increase chance that a neutral pattern will return in 2019, so rainfall amounts are likely to be closer to normal from autumn on in many parts of south-eastern Australia.

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