Faced with the problem of how to estimate and report weather conditions, particularly wind speeds, Admiral Francis Beaufort devised the Beaufort Wind Scale. He first used it 1806 when he was 30 years old, serving as a Lieutenant in the Royal Navy. After being wounded by pirates, he became Hydrographer, or weather expert, to the Admiralty. His method of assessing wind velocity, based on a journal he had kept since first entering the Navy at the age of 13, was formally adopted by the Royal Navy in 1838 and has been used, relatively unchanged, ever since.
The scale was based on the visible effects of the wind, rather than its measured velocity, since this was the easiest way a seaman on watch could assess it.
For reporting purposes, wind-speed and direction was added, especially by the Coast-guard Service and the Meteorological Office, for BBC weather and shipping forecasts. For much of the 20th century, British listeners were regularly regaled with a description of weather conditions in a grid of romantically named sea locations around the British Isles. This was invaluable to seafarers: naval craft, merchant ships, private sailors and fishermen.
It was a regular feature of British meal-times to hear a cultivated voice in the background droning on about “Viking, Cromarty, Forties and German Bight, wind Southeasterly 7 to severe gale 9,visibility moderate or good.”
The reported numbers correspond to wind force. Force 0 is flat calm. At Force 2 small wavelets are evident, described as “light breeze”. “Strong breeze”, Force 6 is identified by the presence of “white horses”. Gale Force 8 is recognised by spindrift blown off the crests of the waves and wind speeds of over 34 knots. (A knot is defined as 1.852 km/h or just over one mile per hour.
At storm Force 10 visibility is affected by blown water. Waves are high with arching crests and sea tumbles heavily. Hurricane is anything over Force 12, 64 knots. The air is blinding with foam and spray. Waves are tremendous and tops are blown sheer off.
Sailing ships were advised to seek harbour at anything over storm Force 9. They were routinely warned of the time-lag between rising wind and visible conditions. The sea was a perilous place and the Beaufort scale of warnings was an invaluable contribution to their safety,
Today, with massive ships fitted with powerful engines and stabilisers, and where the dictates of profit often override those of safety, ships do not rely so much on the Beaufort scale.
With climate change and globalisation we have become aware of the need to rate far more extreme weather conditions both at sea and on land.
The Beaufort scale Force 8 is when slates blow off house roofs. Force 12 is when whole houses blow away at wind speeds of over 64 miles per hour.
To describe stronger winds, since 1971, we have adopted the Enhanced Fujita Scale (EF) for Tornado Damage,
At winds over 72 miles an hour, described as “moderate tornado” (F1), cars are pushed off the road and mobile homes off their foundations. The scale then rises through F2, when mobile homes are demolished and house roofs ripped off, to F3, when trains are derailed and forests uprooted and finally to F5, “Incredible Tornado” with wind speeds of over 300 miles an hour damaging reinforced steel, stripping bark from trees and carrying entire houses and road vehicles up to a hundred yards through the air.
Even in the worst sea storms ever experienced, Admiral Beaufort could never have imagined such devastation.
http://www.r-p-r.co.uk/beaufort.htm
www.metoffice.gov.uk/weather/marine/guide/beaufortscale.html
http://www.stormfax.com/fujita.htm
