The pattern of seasonal rainfall odds across Australia is a result of
continuing higher than average temperatures over parts of the south tropical
Pacific Ocean, and also in parts of the tropical Indian Ocean.
The signal from the Indian Ocean dominates the outlook.
Averaged over spring, the chances are between 60 and 80% for above-normal
maximum temperatures over tropical parts of the country, while over much of
Victoria and adjacent areas of eastern and southeastern SA the chances are
between 60 and 65% (see map).
So in years with ocean patterns like the current, about six to eight September to
November periods out of every ten are expected to be warmer than average over
these regions of the country, with about two to four out of ten being cooler.
In remaining areas, the chances of exceeding the average spring maximum
temperature are mostly between 55 and 60%.
Outlook confidence is related to how consistently the Pacific and Indian
Oceans affect Australian temperatures. During spring, history shows this effect on
maximum temperatures to be moderately consistent across large parts of
the country, with the exception of the southeast and far west
where it is only weakly consistent (see background information). Users therefore need to be
cautious in applying this outlook in Victoria and SA.
Average spring minimum temperatures are favoured to be warmer than normal across
virtually the entire country (see map). The chances of increased overnight warmth (averaged
over the coming three months) are mainly between 60 and 75%, with values
approaching 80% in some areas of the north and west.
History shows the oceans' effect on minimum temperatures during spring to be moderately
to highly consistent over most of the country, except in parts of southeast and eastern
Australia where the effect is generally only weakly consistent.