Gusts and lulls
Wind speed varies due to gusts and lulls. A gust is a sudden increase of wind for a short period, usually a few seconds. A lull is a period of lighter wind.
Forecasts of wind speed and direction are the average across these gusts and lulls, measured over 10 minutes at 10 metres above sea level. Wind speed at the land or sea surface is usually less, due to friction.
The gusts in any 10-minute period can be 40% higher than the average wind speed. For example, when the average wind speed is 25 knots, it is possible to experience gusts of 35 knots and lulls of lighter winds.
Squalls and thunderstorms
A squall is sudden increase in wind speed that is sustained over a few minutes. It is often associated with a passing cold front or thunderstorm.
The gusts in a squall may be more than 40 or 50 knots.
High speed gusts and a line of squalls can form in severe thunderstorms. Learn about thunderstorms and tropical severe thunderstorms in our Severe weather knowledge centre.
Wind blows spray and whips up waves at the mouth of the Mersey River in Tasmania
Wind warnings for mariners
We issue wind warnings to mariners for:
- strong winds
- gale-force winds
- storm-force winds
- hurricane-force winds.
The last 3 categories also prompt warnings to ships on the high seas.
Learn more about wind speed categories and marine wind warnings on our Marine weather hazards and warnings page.