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Weather Information |
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| Beaufort Wind
Scale (Land) |
| Beaufort Number |
Wind |
Effect on land |
Speed (Knots) |
Speed (mph) |
| 0 |
Calm |
Smoke Rises Vertically |
Less than 1 |
Less than 1 |
| 1 |
Light Air |
Direction shown by smoke
but not wind vanes |
1-3 |
1-3 |
| 2 |
Light breeze |
Wind felt on face; leaves
rustle; wind vanes move. |
4-6 |
4-7 |
| 3 |
Gentle breeze |
Leaves & twigs in motion;
wind extends light flag |
7-10 |
8-12 |
| 4 |
Moderate breeze |
Raises dust & loose paper;
moves small branches. |
11-16 |
13-18 |
| 5 |
Fresh breeze |
Small trees in leaf begin
to sway. |
17-21 |
19-24 |
| 6 |
Strong breeze |
Large branches in motion;
whistling in telegraph wires; difficulty with umbrellas. |
22-27 |
25-31 |
| 7 |
Moderate gale |
Whole trees in motion; difficult
to walk against wind. |
28-33 |
32-38 |
| 8 |
Fresh gale |
Twigs break off trees; progress
impeded. |
34-40 |
39-46 |
| 9 |
Strong gale |
Slight structural damage
occurs; chimney pots & slates blown off. |
41-47 |
47-54 |
| 10 |
Whole gale |
Trees uprooted and considerable
structural damage. |
48-56 |
55-63 |
| 11 |
Storm |
Widespread damage; seldom
experienced in UK. |
57-65 |
64-75 |
| 12 |
Hurricane |
Winds of this force rarely
encountered outside tropical revolving storms. |
Over 65 |
Over 75 |
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| Beaufort Wind
Scale (Sea) |
| Beaufort Number |
Wind |
Effect on land |
Speed (Knots) |
Wave Height (m) |
| 0 |
Calm |
Sea like a mirror. |
Less than 1 |
0 |
| 1 |
Light Air |
Ripples formed but without
foam crests. |
1-3 |
0.1 |
| 2 |
Light breeze |
Small wavelets; crests have
glassy appearance but do not break. |
4-6 |
0.2 |
| 3 |
Gentle breeze |
Large wavelets. Crests begin
to break. Perhaps scattered white horses. |
7-10 |
0.6 |
| 4 |
Moderate breeze |
Small waves becoming longer;
fairly frequent white horses. |
11-16 |
1.0 |
| 5 |
Fresh breeze |
Moderate waves, taking more
pronounced long form; many white horses. |
17-21 |
2.0 |
| 6 |
Strong breeze |
Large waves begin to form;
the foam crests are more extensive everywhere. (Probably
some spray.) |
22-27 |
3.0 |
| 7 |
Moderate gale |
Sea heaps up and white foam
from breaking waves begins to be blown in streaks along
the direction of wind. |
28-33 |
4.0 |
| 8 |
Fresh gale |
Moderately high waves of
greater length; The foam is blown into well marked streaks
along direction of wind. |
34-40 |
5.5 |
| 9 |
Strong gale |
High waves. Crests begin
to topple, tumble and roll over. Spray may affect visibility. |
41-47 |
7.0 |
| 10 |
Whole gale |
Very high waves with long
overhanging crests. The sea takes on a white appearance.
Visibility affected. |
48-56 |
9.0 |
| 11 |
Storm |
Exceptionally high waves.
(Small & medium sized ships may be lost to view behind
waves.) Everywhere the edges of wave crests are blown into
froth. Visibility affected. |
57-65 |
11.5 |
| 12 |
Hurricane |
The air is filled with foam
& spray. Sea completely white with driving spray; visibility
seriously affected. |
Over 65 |
>14 |
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| Beaufort Weather
Notation |
| Weather |
Beaufort
Notation |
Weather |
Beaufort
Notation |
| Blue Sky (0-2/8 cloud) |
b |
Snow |
s |
| Overcast (Whole sky covered with
Unbroken cloud) |
o |
Fog |
f |
| Partly Clouded (3/8 to 5/8 cloud) |
bc |
Thunder |
t |
| Squally weather |
q |
Gale |
g |
| Cloudy (6/8 to 8/8 cloud) |
c |
Thunderstorm with rain or snow |
tlr or tls |
| Rain |
r |
Hail |
h |
| Drizzle |
d |
Precipitation in sight |
jp |
| Sleet |
rs |
Ugly threatening sky |
u |
| Wet Air (no Precipitation) |
e |
Dust Haze |
z |
| Unusual Visibility |
v |
Hoar Frost |
x |
| Line squall |
kq |
Lightning |
l |
| Dew |
w |
Dry air |
y |
| Storm of drifting Snow |
ks |
Mist |
m |
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| Windchill
Equivalent Temperature. |
Beaufort
Force |
Wind
Speed
at 10 metre
height |
Air Temperature
°C |
| |
Knots |
ms-1 |
-40 |
-35 |
-30 |
-25 |
-20 |
-15 |
-10 |
-5 |
0 |
5 |
10 |
15
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| 1 |
2 |
0.8 |
-41 |
-36 |
-31 |
-26 |
-21 |
-15 |
-10 |
-5 |
0 |
+5 |
+10 |
+15 |
| 2 |
5 |
2.4 |
-43 |
-38 |
-32 |
-27 |
-22 |
-17 |
-12 |
-7 |
-1 |
+4 |
+9 |
+14 |
| 3 |
8.5 |
4.3 |
-47 |
-42 |
-37 |
-31 |
-26 |
-20 |
-15 |
-9 |
-4 |
+2 |
+7 |
+13 |
| 4 |
13.5 |
6.7 |
-52 |
-47 |
-41 |
-35 |
-30 |
-24 |
-18 |
-12 |
-7 |
-1 |
+5 |
+11 |
| 5 |
19 |
9.3 |
-57 |
-51 |
-45 |
-39 |
-33 |
-27 |
-21 |
-15 |
-9 |
-3 |
+3 |
+9 |
| 6 |
24.5 |
12.3 |
-61 |
-55 |
-49 |
-43 |
-37 |
-31 |
-24 |
-18 |
-11 |
-5 |
+2 |
+8 |
| 7 |
30.5 |
15.5 |
-65 |
-59 |
-52 |
-46 |
-40 |
-33 |
-27 |
-20 |
-13 |
-6 |
+0 |
+7 |
| 8 |
37 |
18.9 |
-68 |
-62 |
-55 |
-49 |
-42 |
-36 |
-29 |
-22 |
-15 |
-8 |
-1 |
+6 |
| 9 |
44 |
22.6 |
-72 |
-64 |
-59 |
-52 |
-45 |
-38 |
-31 |
-24 |
-17 |
-10 |
-2 |
+5 |
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"Windchill" is a term normally
used to express the combined effect of low air temperature
and of wind on a standing or walking human. It can be measured
by the rate of heat loss per unit area, the "windchill
factor" or more commonly by the "windchill equivalent
temperature" (WET). No allowance is made for precipitation
or sea spray. Windchill does not apply to inanimate objects,
even heat producing engines. In "full" sunshine,
a correction of about +7°C at low wind speeds and +3°C at
gale force should be made.
The concept is useful in countries which experience cold winters
to distinguish the difference in human comfort and risk of
exposure between light and strong winds. |
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::Copyright J. Cranston::
2000 -
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