Sir Francis Beaufort was the person who created the Beaufort Wind Scale while he was a Commander in the British Royal Navy in 1806. This scale had 0 to 12 scale categories that indicated how much a ship’s sail would be employed by the wind. In December 1838 his scale was put into use by the British Admiralty for use in all Royal Navy logbooks. Up until 1955 Beaufort numbers were used to scale wind force but then wind velocities were replaced by knots on weather maps.
The Beaufort scale has been revised a few times since it began with 0 12 categories and now it has 17 categories. The Beaufort Wind Scale tells you the average wind speed but also contains a set of wind speed ranges and a description for each category. Additionally, it provides an indication of what the sea looks like at that scale with estimated wave height, along with an observation of what the wind will do on land.
Beaufort Wind Force “0” has an average speed of zero and the range is for any speed less than one knot, mph or kph wind. The descriptions of the wind would be light or calm, the sea would look like a mirror with no wave height and smoke would rise vertically on land.
Beaufort Wind Force “3” has an average speed of 9 knots, 10 mph or 16 kph and the range is 7 to 10 knots, 4 to 7 mph or 6 to 11 kph winds. The descriptions of the wind would be gentle, gentle breeze or slight, the sea would have large wavelets, crests that begin to break and foam of a glassy appearance with wave height of 2 to 3 feet or .6 meters. On land the leaves and small twigs would be in constant motion and the wind would extend small flags.
Beaufort Wind Force “8” has an average speed of 37 knots, 43 mph or 68 kph and the range is 34 to 40 knots, 39 to 46 mph or 62 to 74 kph winds. The descriptions of the wind would be Gale or Very High, the sea would have moderately high waves which crests begin to break into spondrift and the foam is blown in streaks along the direction of the wind with wave height of 18 to 28 feet or 5.5 meters. On land the leaves are blowing like mad and small twigs are breaking off trees and the wind impedes walking.
The last five categories of the Beaufort Wind Force Scale were added to give more defining categories for hurricane force winds. These wind forces are so strong that the Beaufort Wind Scale the descriptions are and as most of us are know, these winds are very destructive and violent storms. At scale 14 the average wind speed is 85 knots, 98 mph or 157 kph, the ranges of wind go 81 to 89 knots, 93 to 103 mph or 149 to 165 kph. On the ocean there is virtually no visibility as the air is filled with foam and driving spray, the waves are over 52 feet or 14 meters high and on land there is great devastation.
Please be aware that I tried to summarize the information here that I found about Beaufort Wind Force Scale on the website www.srh.noaa.gov/srh/jetstream, which is maintained by the National Weather Service. This site is available with lessons on weather and the home page clearly states “You are free to use the materials in any manner you wish.”