Long before the advent of GPS, around-the-clock weather reports, and advanced radar technology, mariners judged the weather by the movement of the wind at sea. The first mariners watched the flags and sails of their ships for subtle changes in wind speed and direction. During this time of high-masted and fully rigged sailing ships, understanding mother nature's method of propulsion was one way a seafarer could measure the safety of any voyage.
Captains also relied on each other for weather, local anchorage, sailing directions, and other important navigation information. Sailors needed to understand each other's methods of measurement and explanation of all things pertaining to the sea. Of course, it's safe to assume that this understanding wasn't always a given between ships. Enter, Admiral Sir Francis Beaufort.
From his time as a young cabin boy aboard British military sailing vessels, Admiral Beaufort realized the importance of keeping a weather journal. He meticulously journaled weather comments and notations every day. Beaufort devised a coded weather description formula and began using it regularly to describe wind and weather patterns in 1805. Beaufort was injured and subsequently assigned to serve as the Hydrographer of the Admiralty, a position of great influence in the British Navy.
As Hydrographer, Beaufort instituted a uniform method of measuring wind intensity based on observed sea conditions. This method was adopted for use by all Admiralty ships in 1938. The original Beaufort Wind Speed Scale analyzed the reactions of sail and rigging to different types of wind. In general, states 0 to 4 were calm weather states, with smooth water and sails clean and full. States 5 to 9 represented brisk winds up to a gale, with full sails and reefing of top sails necessary. Numbers 10 to 12 on the Beaufort Wind Speed Scale reflected the very powerful winds from a strong gale up to a hurricane.
With the advent of steam powered ships, the Beaufort Scale required some adjusting. Wind speed and direction was still very important to vessels as weather indicators. The Beaufort Wind Scale underwent some modifications to describe states of the sea or degree of motions of land reference points such as trees. Modifying the scale meant it could effectively used to describe weather on land, in addition to describing weather at sea.
The International Meteorological Committee changed the Beaufort Wind Speed Scale in 1946 to reflect both land and sea observations. They also added scales 13 to 17 to include hurricane for winds and subsequent destruction. The scales range from 0 which means complete calm, smoke rises directly up, and seas as smooth as a mirror up to 17, which includes winds above 201 knots that is defined by foamed seas with greatly reduced visibility.
Viewing the Beaufort Wind Speed Scale in a tabular, descriptive format just doesn't do it justice. For example, when a newscaster reports that a ship has faced Force 12 winds during a Nor'Easter, the lay person doesn't understand that those winds are clocked at over 108 knots. Since the wind scale is based on movement of water at sea and trees on land, Force 12 winds would violently move trees and cause destruction on land. In the water, waves would spray and foam from the wind force and visibility would be nonexistent.
It's best to view the scale with pictures that much more accurately describe the movement of water and trees. As wind speed gradually increases, its affect on the environment becomes a force to be reckoned with. To see a great visual description of the Beaufort Wind Speed Scale, visit http://www.howtoons.com/toon/the-beaufort-scale.