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Weather patterns
The weather patterns that move across Australia are part of a complex system of air masses that circulate the earth. These air masses follow a pattern that varies with the seasons. Large bands of air thousands of kilometres wide circumnavigate the globe. Massive convection currents move air between the equator and the poles.
Weather systems slowly move from west to east across southern Australia. A weather pattern crossing over Perth will reach New South Wales in a modified form approximately three to four days later. In northern Australia the weather systems tend to move from east to west except for cyclones.
Summer weather patterns
Figure 5 shows the typical summer weather pattern occurring over Australia. High pressure systems migrate from west to east across southern Australia and the Great Australian Bight. They are associated with a cycle of hot, dry weather followed by cooler, moister southerly changes.
A series of low pressure cells develops to the north of Australia. They bring summer rainfall to northern and eastern Australia. In the tropical north this season is known as ‘the wet’. The low pressure cells may develop into cyclones.
Figure 5: Typical summer weather pattern over Australia
Winter weather patterns
In winter the air masses over Australia move north. Figure 6 shows a high pressure system now lying over central Australia. The highs again move slowly from west to east, punctuated by cold fronts.
These cold fronts develop out of intense low pressure cells in the Great Southern Ocean to the south of Australia. They bring cold weather and rain to south-west and southern Australia, with regular snow falls in the high country of Tasmania and south-eastern Australia.
The low pressure cells that were a feature of the summer weather pattern in the northern part of Australia also move even further north during winter. Northern Australia usually experiences cooler, drier weather during winter known as ‘the dry’.
Figure 6: Typical winter weather pattern over Australia
The weather can often be unpredictable and changeable and wide variations from expected weather patterns can occur at any time throughout the year.
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