While it’s certainly possible to measure wind speed with an anemometer, looking out the window is often good enough.
That’s because, back in 1805 Admiral Sir Francis Beaufort developed this handy scale for guessing wind speed based on the sort of observations that can be made out a window. As windspeeds increase, Beaufort’s scale starts to look positively superior to an anemometer. With my little handheld anemometer, I have to go stand out in the weather and hold it. Beaufort’s scale? I can make my estimate from the inside, a decided virtue.
While Beaufort’s scale isn’t going to be useful in all situations (a still summer’s day, when no fires are burning, for example), it’s still pretty handy. And, the times its most useful coincide nicely with the times I’d rather be indoors watching the storm instead of standing in it.
According to Beaufort’s scale, that little whirlwind we had last fall, having caused some structural damage, was probably somewhere between 55 and 60 miles per hour.
With roofing torn off, the wind was definitely more than a “Fresh Gale: Twigs and Small Branches broken off trees”. The next level, a “Strong Gale” has slates blown from roofs. While I’m no expert on roofing, the damage seems to be a bit worse than that. So, probably in the “Whole Gale”, or 55-60 range.
In that instance, using Beaufort’s scale seems far safer than standing outside with an anemometer, even if the machine would be more precise.
Trego's Mountain Ear 