Gusts and lulls
Wind is made up of 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 between gusts.
Forecasts of wind speed and direction are the average of 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 are typically 40% higher than the average wind speed. For example, when the average wind speed is 25 knots, it is normal to experience gusts of 35 knots and lulls of lighter winds.
Squalls and thunderstorms
A squall is an abrupt and large increase in wind gusts. A squall can arrive suddenly and be experienced over a sustained period of many hours.
Each gust usually only lasts for minutes then diminishes suddenly. The gusts in a squall may exceed 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 three 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.