The pattern of seasonal maximum temperature odds across 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 southern 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.
Over the rest of the country, the chances of exceeding the three-month median maximum
temperature are mainly between 40 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
the country (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
southwestern Australia (see map). In contrast a region in northwest Australia has an increased chance of
cooler conditions, with only a 35 to 40% chance of exceeding the winter
median minimum temperature.
Over the rest of the country the odds are in
the 40 to 60% range, so the chances of being warmer than average are
similar to the chances of being cooler.
History shows the oceans' effect on minimum temperatures in winter
to be moderately consistent over large parts of the country,
except over Victoria, Tasmania and parts of southeast SA where the
influence is only weakly or very weakly consistent.