The pattern of seasonal maximum temperature odds across WA
is a result of the combined effects of above average temperatures
in the Indian Ocean surrounding the west coast of WA, and a
warming trend in the Pacific. The Indian Ocean signal dominates the
Averaged over July to September, the chances of above-normal maximum
temperatures increase from around 60% in the southern Kimberley to
between 70 and 80% over most of WA, with 80 to 85% chances in parts
of western WA (see map). So for every ten years
with ocean patterns like the current, about six to eight September
quarters are expected to be warmer than average over most of WA,
with about two to four being cooler.
For the northern Kimberley, the chances of exceeding the three-month
median maximum temperature are between 50 and 60%. So the chances of
being warmer than normal are about the same as the chances of being cooler.
Outlook confidence is related to how consistently the Pacific and Indian
Oceans affect Australian temperatures. During July to September, history shows this
effect on maximum temperatures to be moderately consistent in WA (see background information).
The outlook for average minimum temperatures, shows warmer nights are favoured
in western, central and southern WA. The chances of above median minimum
temperatures over the July to September period are generally between 60 and
70% (see map) in these parts. For the rest of the state, the odds are between
40 and 60%, so the chances of being warmer than normal are about the same
as the chances of being cooler.
History shows the oceans' effect on minimum temperatures in July to
September to be moderately consistent over the southern half of WA.