North-west cloudbands

Learn how north-west cloudbands influence climate in Australia

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What are north-west cloudbands?

A north-west cloudband is a broad layer of cloud. It can stretch from north-west to south-east Australia.

How north-west cloudbands affect Australia

North-west cloudbands affect much of north-western, central and south-eastern Australia. They can bring widespread, and sometimes heavy, rainfall.

These cloudbands generally happen between March and October. They are most frequent between April and September, lasting from a few days to a week.

Map of Australia with blue shading to show where north-west cloudbands occur. Blue shading radiates from a diagonal line between Broome in Western Australia and Sydney in New South Wales.
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North-west cloudbands can affect north-western, central and south-eastern Australia between March and October. They happen most often between April and September, lasting from a few days to a week.

How north-west cloudbands develop

The cloudband develops from warm, moist tropical air that is drawn across the Indian Ocean. This air generally moves in a south-easterly direction. A cloudband forms when the air rises over colder air in the mid-latitudes.

Typically, this happens when tropical air north-west of Australia moves toward the cooler south. It flows along the western flank of a high pressure system over eastern Australia. The warmer air is forced to rise as it passes over cooler air, forming clouds.

Climate drivers related to north-west cloudbands

Cold fronts and cut-off lows

North-west cloudbands can also interact with:

When this happens over south-eastern Australia, it can lead to:

  • deeper or thicker cloud
  • periods of very heavy rainfall across central and south-eastern Australia.

This is called a tropical/extratropical interaction.

Indian Ocean Dipole

North-west cloudbands may also have links with the Indian Ocean Dipole. When sea surface temperatures north-west of Australia are warmer than average, the cloudbands may:

  • happen more often
  • bring heavier rainfall.

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