A wind is the flow of air, formed by uneven heating of the earth's surface by the sun, usually from a high pressure-area to a low-pressure area. In the case of hurricanes or typhoons, ie. tropical cyclones, the wind is the most important physical quantity in the atmosphere.
Wind can be measured by its speed and the direction of the flow. In the meteorology agencies’ warnings and advisories, or in the scientific papers and studies, the wind means (sustained) winds speed or it’s direction in the most cases, depending on the context.
The hurricane, typhoon or cyclone warnings and advisories typically report maximal sustained winds and the gusts. What does maximum sustained wind speed and the wind gust mean? Let’s answer those questions.
What is sustained wind speed
Sustained winds (or simply winds) means winds sustained for a minimum time of at least 1 minute. Optimal mean wind speed is measured mostly for 1 to 15 minutes to avoid the influence of little turbulences in the atmosphere. Basic rule of thumb is that if not stated otherwise, the term max. sustained winds means maximum 10-minute sustained winds.
What is the wind gust
In meteorology, the wind is bounded with another quantity – the wind gusts, or simply gusts. Wind gusts are the highest immediate wind speeds measured in some time. That gives another point of view on the wind.
Take Typhoon Kammuri (Tisoy in PAR) (seen below) as an example. On December 2nd at 6 p.m. UTC, typhoon Kammuri's maximum sustained winds were 105 kts km/h (194 km/h or 121 mph) with gusts of up to 130 kts (241 km/h or 150 mph). That means that the average wind speed was 194 km/h (121 mph), but for a few seconds in that one minute, the wind speed was at 241 km/h (150 mph).
Aside from how the wind is measured, another important metric that helps to determine or forecast cyclone’s intensity is the air pressure. Let’s get back to metrics of the wind itself.
Wind direction and the track
In the case of the tropical cyclone, which is rotating, another important item to forecast is its track and the extent of its winds. National meteorological agencies in the affected areas are issuing warning cones, typically once the storm intensifies at least to a tropical depression (learn more about the four stages of the tropical cyclones here). The cone shows the forecast track, the storm’s intensity (ie. tropical storm, hurricane, tropical depression), and the extent of the winds (radius).
Even in the case of regular non-hurricane wind, it’s helpful to know its direction, or the track direction in the case of a cyclone. That’s typically reported in degrees or as an abbreviation, such as SW for southwest, NNE for north-north east, etc. The wind direction shown on Windy's picker can be set to degrees or an abbreviation in the Settings. Please note what's shown there is the direction of the wind, not the track (in the case of tropical cyclones).
Prague based student of meteorology eager for science, who likes to learn, but also wants to live to the fullest every day. Follow me on Twitter.