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Weather for Petersfield
Today Thursday Friday Saturday Sunday Monday
It is forcast to be Mostly Cloudy at 7:00 PM GMT on December 12, 2018
Mostly Cloudy
9°/3°
It is forcast to be Partly Cloudy at 7:00 PM GMT on December 13, 2018
Partly Cloudy
6°/-2°
It is forcast to be Partly Cloudy at 7:00 PM GMT on December 14, 2018
Partly Cloudy
5°/1°
It is forcast to be Rain at 7:00 PM GMT on December 15, 2018
Rain
8°/6°
It is forcast to be Chance of Rain at 7:00 PM GMT on December 16, 2018
Chance of Rain
11°/4°
It is forcast to be Partly Cloudy at 7:00 PM GMT on December 17, 2018
Partly Cloudy
10°/7°

Beaufort Scale

The Beaufort Scale is an emprical measure for describing wind speeds.
The scale was created in 1806 by Sir Francis Beaufort an Irish born, British Admiral and Hydrographer. The scale consists of thirteen classes:-

Force

Beaufort Scale

Speed (MPH)

0 Calm – Smoke rises vertically Less than 1
1 Light Air – Smoke shows direction 1-3
2 Light Breeze – Wind felt, weather vanes move 4-7
3 Gentle Breeze – Leaves in motion light flag extended 8-12
4 Moderate Breeze – Dust raised, small branches move 13-18
5 Fresh Breeze – Small trees in leaf sway 19-24
6 Strong Breeze – Large branched in motion 25-31
7 Moderate Gale – Whole trees in motion 32-38
8 Fresh Gale – Twigs break off, walking impeded 39-46
9 Strong Gale – Slight structural damage to buildings 47-54
10 Whole Gale – Trees uprooted, severe building damage 55-63
11 Violent Storm – Widespread damage to structures 64-75
12 Hurricane – Massive widespread damage to structures Above 75

How windy is it?

With sound we all know when an engine is noisy, but it is only by using a meter that we know how noisy. The same applies to wind speeds. Of course we dont need to set up an anemometer to know if it is windy, but often our estimation of wind speed is not very accurate and can be influenced by such things as chill factors etc.

This was a serious problem for seamen for many years as there were several systems for judging wind speeds in use. So at the beginning of the 19th century, Admiral Sir Francis Beaufort devised his famous scale. This covered 13 wind strengths based upon the number of sails a full rigged ship could carry. This scale was used for 100 years, when it was changed to make it more useful to landlubbers (and now aeromodellers).
The speeds are in m.p.h. which is how the forecasters show them on T.V. In full size aviation wind information is gven as “Wind Vectors”.
For example 270/15. So the wind is due west at 15 knots.

1 knot = 1 nautical mile per hour. A nautical mile is 6080 ft.
Thus a wind speed of 20 knots = about 23 m.p.h.