Wind

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Wind Deflection

Crosswind has an interesting and surprizing effect on bullets. Small crosswind components can have a big effect on light bullets.

Wind Deflection in inches at 100 yards for crosswind component in mph

Bullet Parameters		Crosswind Component in MPH
Bullet weight (grains)	Muzzle Velocity (fps)	2	4	6	8	10	15	20	25	30
52	3000	0.3	0.6	0.9	1.2	1.5	2.2	2.9	3.7	4.4
69	3000	0.2	0.4	0.6	0.8	1.0	1.6	2.1	2.6	3.1
77	3000	0.2	0.3	0.5	0.7	0.9	1.3	1.7	2.2	2.6
80	3000	0.1	0.3	0.4	0.6	0.7	1.1	1.5	1.8	2.2
77	2800	0.2	0.4	0.6	0.8	0.9	1.4	1.9	2.4	2.8
80	2800	0.2	0.3	0.5	0.6	0.8	1.2	1.6	2.0	2.4

The Beaufort Wind Scale

The Beaufort Wind Scale is named after Sir Francis Beaufort, an admiral in the British Navy. He developed the scale in 1805 in order to estimate wind speed by noting how sails move in the wind. It turned out to be a great help and was later adapted for use on land.

Beaufort MPH KTS Term Description

0 0-1 0-1 Calm Calm; Smoke rises vertically

1 1-3 1-3 Light Air Direction of wind shown by smoke drift, not by weather vane

2 4-7 4-6 Light Breeze Wind felt on face; leaves rustle; Weather vanes moved by wind

3 8-12 7-10 Gentle Breeze Leaves and small twigs in constant motion; Wind extends a light flag

4 13-18 11-16 Moderate Breeze Raises dust and loose paper; Small branches moved

5 19-24 17-21 Fresh Breeze Small trees in leaf begin to sway

6 25-31 22-27 Strong Breeze Large branches in motion; Whistling heard in power lines; Umbrellas used with difficulty

7 32-38 28-33 Near Gale Whole trees in motion; inconvenience felt when walking against wind

8 39-46 34-40 Gale Breaks twigs off trees; impedes walking progress

9 47-54 41-47 Strong Gale Slight structural damage occurs

10 55-63 48-55 Storm Trees uprooted; Considerable Damage

11 64-72 56-63 Violent Storm Widespread damage

12 73-82 64-71 Hurricane Widespread damage

Beaufort	MPH	KTS	Term	Description
0	0-1	0-1	Calm	Calm; Smoke rises vertically
1	1-3	1-3	Light Air	Direction of wind shown by smoke drift, not by weather vane
2	4-7	4-6	Light Breeze	Wind felt on face; leaves rustle; Weather vanes moved by wind
3	8-12	7-10	Gentle Breeze	Leaves and small twigs in constant motion; Wind extends a light flag
4	13-18	11-16	Moderate Breeze	Raises dust and loose paper; Small branches moved
5	19-24	17-21	Fresh Breeze	Small trees in leaf begin to sway
6	25-31	22-27	Strong Breeze	Large branches in motion; Whistling heard in power lines; Umbrellas used with difficulty
7	32-38	28-33	Near Gale	Whole trees in motion; inconvenience felt when walking against wind
8	39-46	34-40	Gale	Breaks twigs off trees; impedes walking progress
9	47-54	41-47	Strong Gale	Slight structural damage occurs
10	55-63	48-55	Storm	Trees uprooted; Considerable Damage
11	64-72	56-63	Violent Storm	Widespread damage
12	73-82	64-71	Hurricane	Widespread damage