When the wind blows

St Jude’s Storm on 28th October whipped up a media frenzy and brought lashings of rain, but not much in the way of wind to north Wales. Not even a gale, never mind a severe gale, or a storm force wind. But what do these descriptors of wind actually mean?

Well, the classifications date back to the beginning of the 19th Century and the observations of Sir Francis Beaufort, a Rear Admiral in the Royal Navy. His classification became known as the Beaufort wind force scale and it still provides the reference for wind speed descriptions today.

A regular gale has windspeeds averaging 37 knots per hour (about 42 miles per hour) with the upper limit being 46mph. If the wind blows at that speed for more than 10 minutes it is classed as a gale. Within the gale there can be gusts with a much faster windspeed, but they don’t change the underlying descriptor as being “a gale”. In a gale trees will sway, twigs will snap and you’ll need to lean hard into the wind to make headway if you’re out walking against it.

The Beaufort wind force scale
The Beaufort wind force scale

If the wind speeds up to an average of about 50mph, that’s a severe gale. And if the wind gets up to an average of 60mph, that is classed as a storm. Storm force winds are quite likely to uproot or snap trees.

nb:(all the mph figures are rounded from the knots per hour figures which are the actually measure used in the Beaufort wind force scale)


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