Common Meteorological Terms and Their Meanings - Wind
Current Wind Speed
Average Wind Speed
Wind Direction
Units
m/s | km/h | mph | knot | |
---|---|---|---|---|
1 m/s = | 1 | 3.6 | 2.236936* | 1.943844* |
1 km/h = | 0.277778* | 1 | 0.621371* | 0.539957* |
1 mph = | 0.44704 | 1.609344 | 1 | 0.868976* |
1 knot = | 0.514444* | 1.852 | 1.150779* | 1 |
(* = approximate values)
Source: Wikipedia
You can find out more about knots on Wikipedia including how the measurement got it's name.
The Beaufort scale
Measuring wind can be difficult. Usually it's done using an instrument called an anemometer. These look like a 4 small cups that rotate around a central point. The speed of rotation is then used to calculate the wind speed.
When you don't have the right equipment at hand there is a good way of estimating wind strength, devised by Francois Beaufort in 1805. During this time weather observations from ships were being made, but there was no fixed description for these observations. One person might describe a wind as a gentle while the other might describe the same wind as strong. Francois Beaufort devised a scale which effectively solved this issue, and the descriptions are still often used today.
Beaufort number | Description | Wind speed | Wave height | Sea conditions | Land conditions |
---|---|---|---|---|---|
0 | Calm | < 1 knot < 1 mph < 2 km/h < 0.5 m/s | 0 ft (0 m) | Sea like a mirror | Smoke rises vertically. |
1 | Light air | 1–3 knots | 0–1 ft | Ripples with appearance of scales are formed, without foam crests | Direction shown by smoke drift but not by wind vanes. |
1–3 mph | |||||
2–5 km/h | 0–0.3 m | ||||
0.5–1.5 m/s | |||||
2 | Light breeze | 4–6 knots | 1–2 ft | Small wavelets still short but more pronounced; crests have a glassy appearance but do not break | Wind felt on face; leaves rustle; wind vane moved by wind. |
4–7 mph | |||||
6–11 km/h | 0.3–0.6 m | ||||
1.6–3.3 m/s | |||||
3 | Gentle breeze | 7–10 knots | 2–4 ft | Large wavelets; crests begin to break; foam of glassy appearance; perhaps scattered white horses | Leaves and small twigs in constant motion; light flags extended. |
8–12 mph | |||||
12–19 km/h | 0.6–1.2 m | ||||
3.4–5.5 m/s | |||||
4 | Moderate breeze | 11–16 knots | 3.5–6 ft | Small waves becoming longer; fairly frequent white horses | Raises dust and loose paper; small branches moved. |
13–18 mph | |||||
20–28 km/h | 1–2 m | ||||
5.5–7.9 m/s | |||||
5 | Fresh breeze | 17–21 knots | 6–10 ft | Moderate waves taking a more pronounced long form; many white horses are formed; chance of some spray | Small trees in leaf begin to sway; crested wavelets form on inland waters. |
19–24 mph | |||||
29–38 km/h | 2–3 m | ||||
8–10.7 m/s | |||||
6 | Strong breeze | 22–27 knots | 9–13 ft | Large waves begin to form; the white foam crests are more extensive everywhere; probably some spray | Large branches in motion; whistling heard in telegraph wires; umbrellas used with difficulty. |
25–31 mph | |||||
39–49 km/h | 3–4 m | ||||
10.8–13.8 m/s | |||||
7 | High wind, moderate gale, near gale | 28–33 knots | 13–19 ft | Sea heaps up and white foam from breaking waves begins to be blown in streaks along the direction of the wind; spindrift begins to be seen | Whole trees in motion; inconvenience felt when walking against the wind. |
32–38 mph | |||||
50–61 km/h | 4–5.5 m | ||||
13.9–17.1 m/s | |||||
8 | Gale, fresh gale | 34–40 knots | 18–25 ft | Moderately high waves of greater length; edges of crests break into spindrift; foam is blown in well-marked streaks along the direction of the wind | Twigs break off trees; generally impedes progress. |
39–46 mph | |||||
62–74 km/h | 5.5–7.5 m | ||||
17.2–20.7 m/s | |||||
9 | Strong/severe gale | 41–47 knots | 23–32 ft | High waves; dense streaks of foam along the direction of the wind; sea begins to roll; spray affects visibility | Slight structural damage (chimney pots and slates removed). |
47–54 mph | |||||
75–88 km/h | 7–10 m | ||||
20.8–24.4 m/s | |||||
10 | Storm whole gale | 48–55 knots | 29–41 ft | Very high waves with long overhanging crests; resulting foam in great patches is blown in dense white streaks along the direction of the wind; on the whole the surface of the sea takes on a white appearance; rolling of the sea becomes heavy; visibility affected | Seldom experienced inland; trees uprooted; considerable structural damage. |
55–63 mph | |||||
89–102 km/h | 9–12.5 m | ||||
24.5–28.4 m/s | |||||
11 | Violent storm | 56–63 knots | 37–52 ft | Exceptionally high waves; small- and medium-sized ships might be for a long time lost to view behind the waves; sea is covered with long white patches of foam; everywhere the edges of the wave crests are blown into foam; visibility affected | Very rarely experienced; accompanied by widespread damage. |
64–72 mph | |||||
103–117 km/h | 11.5–16 m | ||||
28.5–32.6 m/s | |||||
12 | Hurricane force | ≥ 64 knots | ≥ 46 ft | The air is filled with foam and spray; sea is completely white with driving spray; visibility very seriously affected | Devastation. |
Source: Wikipedia
Maximum wind gust recorded
The maximum wind ever recorded was in 1996 on Barrow Island in Australia. Maximum wind gusts were 253 miles per hour (407 km/h) during Tropical Cyclone Olivia.
Previous to that the record was held by the Mount Washington Observatory in New Hampshire, in the United States of America. This occurred on April 12 1936 and was 236 miles per hour (379 km/h). Although the station no longer holds the record, you can read about what it was like to experience such a wind on their website.
If you have any questions or comments on this article, or you think something might be missing, feel free to post your comments below. Otherwise enjoy the other articles in this series
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