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Beaufort Scale Extrapolation

Posted: Fri 04 Feb 2011 2:03 pm
by timfy
I'm sure that this has been raised before...

I'm in the lucky position of having a number of local people follow my weather website and a good few of them commented on the following:

Yesterday we had gusts of wind to 98.9mph and sustained winds of over 50mph. Cumulus, despite showing these windspeeds, still only reported a F4 Moderate Breeze

Today is still stormy, with gusts to 68mph and sustained 10min averages of 30-40mph, beaufort reports F5/F6

What are the beaufort scale readings extrapolated from within cumulus? It seems a little ridiculous to see moderate breeze reported as you watch trees coming down and your dustbin go into orbit :o

It would be nice if a user could change the default from whatever it currently is to extrapolating from 10 min average, latest windspeed or latest gust. As far as meteorological reporting goes it may be a little "off the specs" but for the layman it would show a more accurate snapshot.

www.timfy.ie/weather/

Re: Beaufort Scale Extrapolation

Posted: Fri 04 Feb 2011 2:10 pm
by steve
The Beaufort Scale applies to average/sustained wind speeds. Cumulus provides the Beaufort number and description from whatever you have your average speed calculation set to (but it should really be a 10-minute average).

An average speed of 50 mph is 'Strong gale' Force 9, so I would hope that's what Cumulus was actually showing. I'm not aware of any other reports of it ever getting it wrong.

Re: Beaufort Scale Extrapolation

Posted: Fri 04 Feb 2011 2:25 pm
by timfy
Hi Steve...

The problem may be down to the peculiar geography of where I live... we are in the middle of a mountain range and tend to get huge gusts followed by a brief lull, followed again by big blows as the air that is forced up behind the mountains crashes over and back down on top of us. (Average wind direction is down :) )

Today for instance it is swinging from almost dead air to nearly 70mph gusts every few minutes. Net result is an accurate wind average that doesnt really reflect on the actual conditions.

It's fine on a settled day but during the "Connemara Blows" it is, despite being technically accurate, a bit redundant.

For now I'll just take the ribbing from the local farmers in the pub when I let them know that a moderate breeze blew down their barn :lol:

All the best

Tim

Re: Beaufort Scale Extrapolation

Posted: Fri 04 Feb 2011 2:37 pm
by steve
Rather than use the Beaufort Scale (which is, after all, really intended for use at sea), you could always invent your own scale of descriptions for your web site that suit your local conditions and describe gusts rather than sustained speeds: e.g. Gusting to 90 mph - "Oops, there goes the barn".