STABLE air over large portions of continental Australia continue to “heat up” the inland with the prospects for extended heat wave conditions remaining high for large areas of the country.
However, many of the longer term climate indicators remain inconclusive.
Of temporary good news at least, the sea surface temperature (SST) patterns across the Pacific that indicated a weak El Nino for much of the past two months have returned to a neutral pattern while the SSTs around eastern and southern Australia remain well up on normal.
However, evidence from the US indicates that the world’s oceans in 2018 were the warmer ever recorded beating the record set last year (which in turn, beat the then record set in 2016).
The effects these ocean temperatures will eventually have on the climate of Australia (apart from helping to cause higher temperatures) remains unknown.
The link between the ocean and atmospheric patterns in the Pacific continue to be weak.
Although the surface and sub surface ocean temperature pattern indicated a weak El Nino in place for the past six to eight weeks of 2018, the atmosphere never reflected this. In fact, one major atmospheric indicator, the Southern Oscillation Index has remained positive which is strongly in the neutral range, as has the strength of the south-eastern trade winds across the tropical western Pacific.
Nevertheless, the majority of international models continue to predict a weak El Nino (in ocean temperature patterns) to continue through into autumn, despite the atmospheric circulation over the tropical Pacific not yet showing evidence of linking with these oceans patterns.
Around early autumn has tended to be the most favourable time for such linking to occur in the past so for that reason alone some forecasters still believe weak El Nino conditions will emerge shortly.
However, given the timing and its potential weakness, its impacts are not anticipated to be at all significant.
So the potential for the so called significant “one off” rain event continues to remain reasonable good.
As indicated previously, however, such events do not produce general rain but patchy, variable and locally useful falls - helping in areas they effect, but insufficient at this stage to overcome the shortfalls of the past year or two.
In the short term, the “reluctance” of the northern monsoon to establish itself has meant further heating of the air over the north-west of the country and this continues to lift the chance of higher than normal temperatures across south-eastern Australia in the next two months.