The pattern of seasonal maximum temperature odds across western Australia
is a result of the combined effects of above average temperatures
in the Indian Ocean immediately to the west of Australia and cooler than average
waters in the central to western equatorial Pacific in association with the decaying
La Niña pattern.
Averaged over winter, the chances are between 60 and 70%
for above-normal maximum temperatures in the western half of WA
(see map). So for every ten years with ocean patterns
like the current, about six or seven winter periods are
expected to be warmer than average over this part of the
country, with about three or four being cooler.
For the rest of the state, the chances of exceeding the
three-month median maximum temperature are mainly 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 winter, history shows
this effect on maximum temperatures to be moderately consistent over most
of WA (see background information).
Similar to the maximum temperature outlook, the chances of above median
minimum temperatures over the winter period are between 60 and 70% in
the western half of WA (see map). In contrast the Kimberley region has
an increased chance of cooler conditions, with only a 35 to 40% chance
of exceeding the winter median minimum temperature.
History shows the oceans' effect on minimum temperatures in winter
to be moderately consistent over large parts of WA, except over parts
of the Kimberley where the influence is only weakly or very weakly consistent.