Economist Style Guide - Redress Information & Analysis

Beaufort Scale
For devotees of the shipping forecast, here is the World Meteorological
Organisation’s classifi cation of wind forces and effects.
Conditions (abbreviated) Equivalent speed at 10m height
Force Description On land At sea knots miles per
hour
0 Calm Smoke rises
vertically
Sea like a mirror less
than 1
less
than 1
metres per
second
0.0–0.2
1 Light air Smoke drifts Ripples 1–3 1–3 0.3–1.5
2 Light breeze Leaves rustle Small wavelets 4–6 4–7 1.7–3.3
3 Gentle Wind extends Large wavelets, 7–10 8–12 3.4–5.4
breeze light fl ag crests break
4 Moderate
breeze
5 Fresh
breeze
6 Strong
breeze
7 Moderate
gale or near
gale
8 Fresh gale
or gale
Raises paper
and dust
Small trees in
leaf sway
Large branches
in motion
Whole trees in
motion
Breaks twigs off
trees
9 Strong gale Slight structural
damage
10 Whole gale
or storm
Trees uprooted,
considerable
structural
damage
Small waves,
some white horses
Moderate waves,
many white
horses
Large waves form,
some spray
Sea heaps up,
white foam streaks
Moderately high
waves, wellmarked
foam
streaks
High waves, crests
start to tumble
over
Very high waves,
white sea tumbles
11–16 13–18 5.5–7.9
17–21 19–24 8.0–10.7
22–27 25–31 10.8–13.8
28–33 32–38 13.9–17.1
34–40 39–46 17.2–20.7
41–47 47–54 20.8–24.4
48–55 55–63 24.5–28.4
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