The Beaufort wind force scale used to indicate weather conditions is well known to anyone who has heard the BBC's shipping forecast. The original scale as created by Sir Francis Beaufort related to what he saw as the different states of sea condition which affected a sailing warship - a "well-conditioned man-of-war."

Wind speed was not actually mentioned in the scale, but rather the force that was exerted on a Man-of-war. The descriptions for Beaufort numbers 0 through to 4 describe the wind in terms of the speed that it may propel the ship; those for 5 through to 9 in terms of her mission and her sail carrying ability; and those for 10 through to 12 in terms of her survival.

The Royal Navy made Beaufort's scale mandatory in 1838 but it wasn't until 1912 that the International Commission for Weather Telegraphy sought some agreement on velocity equivalents for the Beaufort scale. A uniform set of equivalents was accepted in 1926 and revised slightly in 1946. By 1955, wind velocities in knots replaced Beaufort numbers on weather maps. But there were still a need for eyeball estimates by seamen to fill the gaps in the global observing network. Thus it became imperative to relate the seaman's guess logged in Beaufort numbers to the wind speed in knots. And so Beaufort's scale had transfomed itself from a tool of the mariner to a means for the meteorologist.