Beaufort scale

K

KeithH

Well-Known Member
Joined
23 Sep 2002
Messages
174
Location
W Sussex, UK
Visit site
I can find lots of sources of the definition of the Beaufort number, but it is not clear to me when, say a force 3 becomes a force 4.

For instance, F3 is defined as 7-10 knots, and F4 as 11 - 16 knots.
So what number is a wind at 10.5 knots?

It could mean >10 so a F4, or <11, so a F3.

I am sure that it must be defined somewhere. Any weather experts know?
 
When the met. office quote a wind speed they are stating an average number, over 3 minutes' record on an anemograph, and if I recall correctly it is recorded to the nearest knot. Mathematically, 10 to 10.49999 = 10, above that it will be recorded as 11.
 
[ QUOTE ]
Met Office site has all the answers as usual.

[/ QUOTE ] But the link does not work.

Or does it?
 
7-picture.jpg


Any help?
 
The modified Beafort scale is much much better and can be found in the book the "Art of Course Sailing"
This is much more pragmatic and Force 5 is defined as the speed at which the foam blows off the top of a pint of bitter. Of course this absolutely confuses lager drinkers ( serve em right)
 
[ QUOTE ]
the "Art of Course Sailing"

[/ QUOTE ]

"The Art of Coarse Sailing", I think you mean, by Michael Green. /forums/images/graemlins/ooo.gif

I've got "The Art of Coarse Cruising". Its not in there!
 
[ QUOTE ]
For instance, F3 is defined as 7-10 knots, and F4 as 11 - 16 knots.
So what number is a wind at 10.5 knots?

[/ QUOTE ] From a purely mathematical point of view if you round off the windspeed to a whole number speeds upto 10.499999 would round down to 10 but conventionally 10.5 (and above) would round up to 11. So on that basis 10.5 would be F 4.

However if you apply the same logic to the same wind expressed in other units you may not get the same result.

10.5kn = 12.1 mph. That rounds down to 12mph and since F3 is 8-12mph and F4 is 13-18mph that make it a F3!
 
Does it matter?

F4 is windy, F5 is very windy, F6 is worryingly windy, and anything greater than that is purely fiction designed to scare me.
 
[ QUOTE ]
F4 is windy, F5 is very windy, F6 is worryingly windy

[/ QUOTE ]
Ah, but thats all relative to the boat.... /forums/images/graemlins/grin.gif
 
Why is 10.5kts in Beaufort scale important? The Beaufort scale is best for estimating wind speed from observation of wave and swell formation. I have a very handy little book with pictures of various sea conditions for each part of the scale. To which some comdeian has added 13 and the comment "Our father who art
 
I think the scale was originally devised to allow some sort of measure of wind force by looking at the sea state. After all its usually the waves that do the damage not the wind.

This pursuit of precision is a bit pointless!
 
Thanks for all the comments. I agree that the definition of the transition is "academic", but when converting data from windspeed to wind force, in say, a spreadsheet, there needs to be a "rule". My 10.5 kt example was just to illustrate the problem of where to draw the line.
 
As this is so vitally important to you /forums/images/graemlins/wink.gif i have been watching the reported windspeeds and "forces" reported from the Chimet group of weather stations in the solent area.

At present the wind is in the force 2 to 3 range. Force 2 = 4 to 6 knots, force 3 = 7 to 10 knots.

What i have observed is than upto 6.4 knots it is reported as force 2 and from force 6.5 and upwards it is reported as force 3.

Therefore what I suggested earlier appears to be correct. Round off to the nearest whole number (rounding a .5 up).

So in your example 10.5 would be reported as F4, but 10.4 would be reported as F3.

I hope your anemometer is sufficiently accurately calibrated to justify the effort that has gone into this scientific investigation! /forums/images/graemlins/frown.gif

Cheers /forums/images/graemlins/smirk.gif
 
[ QUOTE ]
[ QUOTE ]
F4 is windy, F5 is very windy, F6 is worryingly windy

[/ QUOTE ]
Ah, but thats all relative to the boat.... /forums/images/graemlins/grin.gif

[/ QUOTE ]And the coward on the helm! /forums/images/graemlins/grin.gif
 
[ QUOTE ]
Ah, but thats all relative to the boat

[/ QUOTE ]
F1 Windsurfers snore, dinghy sailors yawn, yots start motor

F2 Windsufers yawn, dinghy sailors launch, yots motor

F3 windsurfers open one eye, dinghy sailors smile, yots think about sailing

F4 windsurfers launch, dinghy sailors sweat and plane, yots stop engines

F5 Windsurfers smile, dinghy sailors capsize, yots reef their G&T's and sails

F6 Windsurfers launch in their thousands, dinghy sailors retire hurt to the bar, yots hand out the quells and think of diverting to a nearby sheltered spot

F7 Can't see the water for wind and kite surfers, dinghy sailors snore, yot crews puke up the G&Ts

F8 Some windsufers retire hurt, dinghy sailors have bad dreams, yots wish they were somewhere else . . .

I could go on . . .
 
You must log in or register to reply here.

Share this page

Top