The Beaufort Scale

Beaufort Scale

Beaufort’s diary from 1806, showing his original scale.

It is often said that Francis Beaufort, of the British Royal Navy, was the first to devise a scale of wind force – towards the start of the 19th century. However, in reality he was not, in fact, the originator of such a scale. A similar one was actually in use at least a century earlier – and probably long before that.
We do not know who first devised a scale of wind force. But it would be surprising if medieval Arab seafarers did not use one because they had, by the late 15th century, classified in detail virtually every aspect of the weather that had any navigational significance. It would be surprising, too, if the mariners of ancient times did not use such a scale – but as they left so few records, we can only speculate.
The scale we all know – the one that bears Beaufort’s name – was formulated at the start of the 19th century. But accounts from 1704 show that a similar scale was in use a century earlier.



The scale is used in the Shipping Forecasts broadcast on BBC Radio 4 in the United Kingdom, and in the Sea Area Forecast from Met Éireann, the Irish Meteorological Service. Met Éireann issues a "Small Craft Warning" if winds of Beaufort Force 6 (min. mean of 22 knots) are expected up to 10 Nautical miles offshore. Other warnings are issued by Met Éireann for Irish coastal waters, which are regarded as extending 30 miles out from the coastline, and the Irish Sea or part thereof: "Gale Warnings" are issued if winds of Beaufort Force 8 are expected; "Strong Gale Warnings" are issued if winds of Beaufort Force 9 or frequent gusts of at least 52 knots are expected.; "Storm Force Warnings" are issued if Beaufort Force 10 or frequent gusts of at least 61 knots are expected; "Violent Storm Force Warnings" are issued if Beaufort Force 11 or frequent gusts of at least 69 knots are expected; "Hurricane Force Warnings" are issued if winds of greater than 64 knots are expected.