Wind speeds in knots are then converted to other units and rounded to the nearest 5 mph or 5 km/h. ![]() Although the scale shows wind speeds in continuous speed ranges, the National Hurricane Center and the Central Pacific Hurricane Center assign tropical cyclone intensities in 5-knot (kn) increments (e.g., 100, 105, 110, 115 kn, etc.) because of the inherent uncertainty in estimating the strength of tropical cyclones. The Saffir–Simpson hurricane wind scale is based on the highest wind speed averaged over a one-minute interval 10 m above the surface. ![]() The classifications can provide some indication of the potential damage and flooding a hurricane will cause upon landfall. The highest classification in the scale, Category 5, consists of storms with sustained winds of at least 157 mph (137 kn, 252 km/h). To be classified as a hurricane, a tropical cyclone must have one-minute-average maximum sustained winds at 10 m above the surface of at least 74 mph (64 kn, 119 km/h Category 1). This measuring system was formerly known as the Saffir–Simpson hurricane scale, or SSHS. The Saffir–Simpson hurricane wind scale ( SSHWS) classifies hurricanes-which in the Western Hemisphere are tropical cyclones that exceed the intensities of tropical depressions and tropical storms-into five categories distinguished by the intensities of their sustained winds. Queries to and quote reference “SS-Wind04”.Saffir–Simpson scale, 1-minute maximum sustained winds Category Note (): Values from 20 are under investigation due to missing data at Valentia Observatory. ![]() Time Series and Trends: Mean annual wind speeds and the number of days per year with gale gusts (a gust of greater than 17.5 m/s or 34kt) are shown below for Valentia and Dublin Airport. Gust speeds are also recorded, as are the times of highest daily gusts and the mean wind speed and direction at the time of the highest gust and the highest 10 minute mean speed in a 24 hour period. Wind speed and direction are continuously recorded and tabulated, either manually or automatically depending on the station location and type. Data used in this section have not been homogenised or corrected for roughness. Inhomogenieties arise in wind data time series due to changes in instrumentation and changes in station exposure due to new buildings, tree growth etc. The wind at a particular location can be influenced by a number of factors such as obstruction by buildings or trees, the nature of the terrain (roughness) and deflection by nearby mountains or hills. Up until the 1990s, wind speed and direction were measured by Dines pressure tube anemometers, these operate on the basis of the pressure caused by the wind blowing into an opening on the wind facing end of a wind vane, since the early 1990s these have been replaced by cup and vane anemometers, with wind speed measured by rotating cups, and direction by a separate wind vane. Wind speed and direction are measured at synoptic weather stations. Wind has been measured in Ireland since the late 19th century. Wind measuring sites need to be open, level and free from obstructions due to buildings and trees etc., for this reason wind speed and direction are measured generally at 10m above ground level. The wind regime at the surface is influenced by local topography. Winds play a key role in the global transport of heat and energy. ![]() Wind is the movement of air caused by pressure differences at the earth’s surface, which in turn are caused by the differential heating of the earth’s surface by the sun. Peer-reviewed journal articles by Met Éireann staff members Past Weather Agrometeorological Bulletins
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