The Beaufort Wind Scale

The weather has been atypical since the beginning of the year, with an unusually long period of dry, frosty weather.  Yesterday this was broken by an unusually rough rainstorm, such that I was concerned about damage to young plants in the garden. Now the BBC RSS feed gives wind speeds in miles per hour (possibly you can choose other units too), but how do you interpret this in terms of damage risk?  The obvious answer is the Beaufort Wind Scale, which devised over 200 years ago for use by mariners, but there is a interpretation of wind effects for landlubbers too, as shown below.

So the weather forecast for yesterday showed a wind speed of 28 mph at my location.  This equates to Force 6 ‘Strong Breeze’ on the Beaufort Scale,  with ‘Larger tree branches moving, whistling in wires’.  Given that this is ‘average wind speed’, there will be stronger gusts, quite probably reaching Force 8, a full gale where twigs break off trees and it is difficult to walk against the wind.

Definitely time to ‘batten down the hatches’, or to us landlubbers, to ensure that delicate plants are properly staked and loose covers are properly fixed down.

Beaufort Wind Scale

Developed in 1805 by Sir Francis Beaufort, U.K. Royal Navy

Force Wind speed
(knots)
Wind speed
(mph)
Wind speed
(km/h)
Wind speed
(m/s)
WMO
Classification
Appearance of Wind Effects
On Land
0 0-1 0-1 0- 1 0-0.2 Calm Calm, smoke rises vertically
1 1-3 1-3 1-5 0.3-1.5 Light Air Smoke drift indicates wind direction, still wind vanes
2 4-6 4-7 6-11 1.6-3.3 Light Breeze Wind felt on face, leaves rustle, vanes begin to move
3 7-10 8-12 12-19 3.4-5.4 Gentle Breeze Leaves and small twigs constantly moving, light flags extended
4 11-16 13-18 20-28 5.5-7.9 Moderate Breeze Dust, leaves, and loose paper lifted, small tree branches move
5 17-21 19-24 29-38 8.0-10.7 Fresh Breeze Small trees in leaf begin to sway
6 22-27 25-31 39-49 10.8-13.8 Strong Breeze Larger tree branches moving, whistling in wires
7 28-33 32-38 50-61 13.9-17.1 Near Gale Whole trees moving, resistance felt walking against wind
8 34-40 39-46 62-75 17.2-20.7 Gale Twigs breaking off trees, generally impedes progress
9 41-47 47-54 75-88 20.8-24.4 Strong Gale Slight structural damage occurs, slate blows off roofs
10 48-55 55-63 89-102 24.5-28.4 Storm Seldom experienced on land, trees broken or uprooted, “considerable structural damage”
11 56-63 64-72 103-117 28.5-32.6 Violent Storm  
12 64+ 73+ 118+ 32.7+ Hurricane  

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