Extra - January 12, 2012
Wind reporting
Summit gusts should be banned

By Philip Eden

We heard and read endlessly in the news media that last Tuesday and Wednesday we had experienced "a 112mph storm". I want to argue that this was an exaggeration on several counts.

First, the wind we experience always comprises a series of momentary gusts and lulls, and it is usual practice among meteorologists to report mean (average) wind speeds. Mean wind speeds at the climax of last week's gale were of the order of 50-60mph. The 112mph that we saw in all those headlines was simply a gust, lasting a couple of seconds.

Second, the standard height for measuring wind speed is 10 metres (33 feet) above the ground, simply because in the lowest six feet of the atmosphere the wind is seriously reduced by friction with the Earth's surface, as well as heavily interfered with by buildings and trees. For meteorological purposes a wind recorded at such a level would be entirely useless.

Third, in addition to the standard national network of anemometers, we also have six high-level wind-reporting sites, some of them atop mountain summits such as Cairn Gorm and Aonoch Mor (next door to Ben Nevis) in Scotland. The gust of 112mph was recorded at one of these: Great Dun Fell, 2625 feet above sea-level, in the northern Pennines. Thus my version of the philosophers' question: "If a wind speed is recorded where no-one lives and where there are no buildings or trees, has it really happened?" Well, of course it has, but is it relevant? No.

By Philip Eden

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