ALTHOUGH the rain event in the north east of NSW last week brought some handy totals, it was generally not as good as expected.
However, the good news is that it signified a slight change in the patterns that have dominated the weather charts in the previous months.
It also introduced the possibility of follow up activity later in the coming week.
However, the long-term prognosis of a developing El Nino event remains the most likely scenario, but its effects could be a little less harmful than originally thought.
The El Niño–Southern Oscillation (ENSO) is still in a neutral phase but model outlooks indicate an El Niño remains the most likely outcome later in the year, with the majority predicting further warming of the tropical Pacific is likely (a sign of an El Nino).
All models suggest El Niño thresholds are likely to be reached by December.
A transition to an El Nino at this time of year can be associated with occasional but brief and significant events.
It can also be associated with a slight increase in severe storm activity especially in November and December. Such activity can give localised useful rainfalls at an otherwise dry time.
However, widespread rain will depend on other factors which are not likely at this stage. One such factor is what happens in the Indian Ocean.
Although the Indian Ocean dipole (IOD) is also neutral at the moment, some models such a short-term positive IOD event is likely to develop and a positive IOD reduces rainfall potential in the south-eastern states and can exacerbate rainfall deficiencies caused by an El Nino.
So, all this increases the dependence of so called one-off events if average rain is to be reached and such events are only about a 30 per cent chance.
The developing pattern continues to favour above average temperatures.
Parts of south-eastern Australia have had a burst of cold weather in August but moving into spring, above average temperatures are very likely and such a trend will persist through summer as well.
