Ahoy - Mac's Web Log

Dear Sir,

I would like to get some clarification on the Beaufort wind scale.

Measuring wind over water gives a World Meteorological Organization description and a Beaufort number (force). Is this the same for wind over LAND?

Does this rating consider a time scale. E.g. If a rating of force 8 (34-40 knots 39-46 mph 62-74 km/h Gale WMO) is announced what variation over time can be expected. I assume wind gusts can not be anticipated but are limits to what can be expected within a time frame?

I noticed that wind speeds are expressed as 'current'. Is this official measurement of time.

What I'm trying to achieve is this:

- If I announce that a 'wind rating' is gale force, should I qualify this by saying it is limited to a time frame and that wind gust up to and including other wind ratings must be anticipated?

- If I say 'current wind rating', is that enough for me to be correct if a different wind rating is measured at a later time?

Are set variations built into a wind-rating announcement. If so what are they?

Are these and any other considerations taken into account when a rating is given?

I'd like to thankyou in advance for any consideration taken in reviewing and answering this email.

Regards,
Karl Brudell
>02 9909 8497

Dear Karl,

Thank you for your E-Mail.

If you look at the Beaufort Wind scale on Ahoy. Mac's Web log you will note the top table is for wind over land, and the second table is for wind at sea.

Essentially they are the same, but use different terms to assist the person
doing the measuring whether at sea or onshore.

I am not aware of any time frame, one estimates the force of the wind at a
time, and I would say the use of the term current indicates exactly that.

If the force changes a new estimate may be made.

At sea, the Officer of the Watch enters the wind force and direction in the ship's log usually at the start of his watch eg at 0800, 1200, 1600, 1800, 2000, 2400 and 0400. and there is a column to enter this detail.

There is a much wider section for remarks, and if you are undertaking a specific task and the wind force is changing, the OOW may enter the changing and increasing wind force here,eg, in HMAS Australia in Otober 1940 we were trying to rescue the crew from a downed Sunderland aircraft in a North Atlantic gale, the wind speed changed, and this is noted in the remarks section.

In two E-Mails I am sending there are two descriptions of  the Beaufort Scale and how it evolved, one shows a pictorial representation of a house in varying wind speeds, I trust they and the  above may be of help.

Best Regards,
Mackenzie Gregory.

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