Your wind speed estimate is probably wrong

And the Beaufort wind force scale is flawed, says storm data researcher

As an avid kite flier, I’m often out in windy conditions. More than once, on a particularly windy day, I’ve guessed at the wind speed, only to be surprised when a handheld anemometer shows a speed as much as 10 mph lower than I guessed. It’s easy to think the wind is blowing stronger than it is. And a recent scientific study proves that.

“Storm reporters overestimated the speeds of wind gusts—on average, by about one third of the gusts’ actual speeds.”

The resulting paper, “Quantitative Assessment of Human Wind Speed Overestimation,” appears in the April, 2016 issue of the Journal of Applied Meteorology and Climatology (JAMC). Its authors report that “storm reporters overestimated the speeds of wind gusts—on average, by about one third of the gusts’ actual speeds,” according to a report on the study in Eos . (Members of the American Meteorology Society may view the full text of the original, JAMC article.)

I learned in SKYWARN storm spotter training that if I don’t have an anemometer, I can estimate wind speeds based on what I see the wind doing, using the Beaufort wind scale as a reference. Supposedly, an estimate based on whether the wind is (for example) causing large tree branches to move (32 to 38 mph, according to the Beaufort scale) is more reliable than an estimate based on how the wind feels against my body.

That might be true, but Beaufort-based estimates are still unreliable, because the Beaufort scale is flawed, study lead author Paul Miller told Eos.

What’s a SKYWARN storm spotter to do? I’ve heard a National Weather Service (NWS) warning coordination meteorologist say many times that damage reports are much more valuable to NWS weather forecast offices than are wind speed estimates. Now that I know my wind speed estimates — even those based on the Beaufort scale — are probably wrong, here’s what I’ll send NWS instead; a detailed description of damage I see the wind doing.

I encourage my fellow storm spotters to likewise report wind damage, rather than estimated wind speeds.

2 thoughts on “Your wind speed estimate is probably wrong”

  1. Thanks for the blog.

    And like all things scientific, ask if what you observe makes sense.

    ‘”Trust, but verify”

    Even automated equipment is fraught with error. Was it calibrated? What is the percentage error and does it differ with speed?

    Home weather stations are generally not installed to WMO/NWS standards and do have errors and often significant errors.

    I have always tried to use the Beaufort wind speed chart to “calibrate” my observation with known good observations (ASOS, AWOS)

    To be honest, I have only personally physically experienced 70 MPH winds once in my life – and it was not pleasant. I have experienced plenty of 30 to 40 mph wind gusts, and a few times in my life where I have witnessed 50 mph winds. It’s hard to calibrate my senses with such limited experience.

    Your blog is spot on, reports of damage are more beneficial and help provide the ‘gut check’ does this make sense?

    Small limbs down 3-5″ diameter and an estimate of 70 MPH winds would be a mismatch if you see no other damage to structures or other nearby trees.

    It’s about descriptive observing. Concise, yet precise. It’s also about practice; even the best athletes require hours and sometimes years of practice.

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