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Why Do Wind Gusts Make Headlines?

November 13, 2015
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By Paul Homewood  

 

 

 

 

As many have pointed out, the use of wind gust speeds seems to have become more prevalent recently, and can lead to an overinflated impression of the strength of a storm.

The BBC has even built gusts into their forecasts, explaining:  

 

image

http://www.bbc.co.uk/weather/features/34616316

 

Frankly, I find their excuse pathetic. It is in fact thoroughly confusing seeing their forecast suddenly switch from 18 mph to 40 mph – what does this mean in reality?

 

 

 

 

According to the Met Office:

 

 

Measuring gusts and wind intensity

Because wind is an element that varies rapidly over very short periods of time it is sampled at high frequency (every 0.25 sec) to capture the intensity of gusts, or short-lived peaks in speed, which inflict greatest damage in storms. The gust speed and direction are defined by the maximum three second average wind speed occurring in any period.

A better measure of the overall wind intensity is defined by the average speed and direction over the ten minute period leading up to the reporting time. Mean wind over other averaging periods may also be calculated. A gale is defined as a surface wind of mean speed of 34-40 knots, averaged over a period of ten minutes. Terms such as ‘severe gale’, ‘storm’, etc are also used to describe winds of 41 knots or greater.

http://www.metoffice.gov.uk/guide/weather/observations-guide/how-we-measure-wind

 

I don’t know how long our technology has been able to measure at quarter second intervals, but this alone must lead to an inflation of gust speeds over older equipment.

It is of course the 10 minute sustained speeds which are used for the well established Beaufort Scale.

I am not aware that the Met Office has published any official Beaufort data for Abigail, but sustained speeds would probably be at least 20 mph less than gusts, making it Storm Force 10 on the Beaufort Scale at its strongest in the Hebrides, Orkney and Shetland. Elsewhere in Scotland, I doubt it made more than a Severe Gale.

[The Scale goes up to 12, which is hurricane strength]

 

One of the effects of this obsession with is that it allows news outlets regularly to talk about “hurricane strength” winds. This is absolute nonsense, as hurricane strength scales are all based on sustained wind speeds, not gusts.

For instance, the Saffir-Simpson scale, which is based on 1-minute sustained speeds, only categorises a storm as a hurricane when it reaches 74 mph. Even at South Uist, it is highly unlikely the Abigail ever reached anywhere near that.

 

The Beaufort Scale has been around since 1805, and has real and critical significance for those who use it. To see it bypassed just for spectacular headlines is short sighted and sums up so much of the reporting of weather/climate issues these days.

18 Comments leave one →
  1. Ian Cunningham permalink
    November 13, 2015 5:59 pm

    Abigail was a non event in Orkney despite an amber warning: maximum gust 61mph and only three hours with sustained windspeeds in excess of 40mph…so a fairly common winter gale and nothing like a storm. The Met Office having extended their yellow alert to cover all of Friday withdrew it as wind speeds dropped to 30-35mph

  2. November 13, 2015 6:34 pm

    If fisherman weren’t intelligent enough to think for themselves reporting wind gusts in forecasts would have the potential to keep the boats in harbour – they should stick to Beaufort scale as then everybody knows where they are

  3. November 13, 2015 6:53 pm

    This is a link to Casper, Wyoming wind speeds. Wind speeds are reported as sustained and gusts. It’s always been done that way. Wyoming has a lot of wind, as you can see. There’s no reason to report only one or the other measurement.

    http://www.wunderground.com/cgi-bin/findweather/getForecast?query=pws:MKTMH

  4. 1saveenergy permalink
    November 13, 2015 10:05 pm

    “Why Do Wind Gusts Make Headlines?”

    Paris …….cos it’s all they’ve got

  5. Green Sand permalink
    November 14, 2015 12:01 am

    “Why Do Wind Gusts Make Headlines?”

    Possibly because we allowed our government to be controlled by PPE graduates?

  6. November 14, 2015 12:59 am

    It’s the wind gusts that do the damage so I like to see wind gust reported. I also like to see the average reported as well as the peak gust for any monitoring time period and for forecasts. The average speed is a better indicator of transport speed for air pollutants.

    The gust to average ratio is greatly affected by surface roughness and also by the averaging time and height of measurement. For a given averaging period, high surface roughness lowers both the gust and average speeds, increases the gust to average ratio, and makes the wind direction much more variable with strong winds, as compared to nearby areas with lower surface roughness.

    I wish the US would switch to 10 minute averages for wind like most of the world. I also wish synoptic weather reports would include wind gust. OK, I’ll get off my soap box now.

  7. Billy Liar permalink
    November 14, 2015 1:27 am

    I think it’s BS to say that it is gusts that do the damage. Imagine you are driving a high sided vehicle. A 0.25 second gust will not tip your vehicle over because of the inertia of the vehicle. A 3 second gust might lift the wheels off the road on one side and give you a big scare but it will take much longer than that to tip the vehicle over. The same applies to such things as tiles on roofs – a brief gust may rattle them but a longer period of high wind is required to pull the nails out that hold the tile in place.

    Brief gusts certainly work with loose items but anything with inertia requires something longer.

    • November 14, 2015 1:39 am

      I agree with most of what you wrote. It takes 55 to 60 mph wind to knock over a semi truck if it’s lightweight. Our roads close to trucks at high sustained wind speeds, but not for gusts.
      Shingles blow off and the nails stay on the roof. I have a whole stack of these gathered from sustained winds first loosening the shingle, then it flaps and then it flies!

  8. Billy Liar permalink
    November 14, 2015 1:37 am

    According to the UKMO mean winds over 30kts are 35-50% of the possible gust speed over land. (I am assuming gusts will not exceed the gradient wind)

    See page 1-10 of:

    http://www.metoffice.gov.uk/media/pdf/p/l/Chapter_1._Wind.pdf

  9. xmetman permalink
    November 14, 2015 11:30 am

    The simple answer is that the gust values are always higher than those for mean speed and will make a much catchier headline!

    Hurricane wind speeds are always measured as a one minute means, and a mean speed of 64 knots or more (Beaufort force 10) could and probably is considerably less than it was measured over 10 minutes rather than just a single minute. Hurricanes use 1 minute means whilst SYNOP observations use 10 minute means, and that’s why it’s impossible to equate wind speed in a hurricane or tropical cyclone with those in an extratropical depression that occurs across our part of the Atlantic.

    Yesterday at Lerwick the 45 knot mean that Abigail produced may have been nearer to 60 knots if they had used a 10 minute mean. With software, it would be quite simple to generate a 1 minute mean as well as a 10 minute mean from a modern AWS. What we want have not come to terms is the greater accuracy and shear number of observations that a modern AWS produce and what that means for measurements of wind speed and temperature.

    https://xmetman.wordpress.com/2015/07/13/is-global-warming-due-to-more-sensitive-thermometers/

    • November 14, 2015 2:58 pm

      I read your post on xmetman. I am curious how one “calibrates” an electronic thermometer and how often that’s done. In the past, people tended to ignore (scientists included) how important calibration was. With a mercury thermometer, there were exact calculations for amount of mercury, diameter of tube and spacing of markings. How is the electrical resistance calibrated and how often? Just curious.

      • xmetman permalink
        November 14, 2015 4:48 pm

        I’m not at all sure how it’s done myself. It maybe that they use some kind of very accurate mercury reference thermometer and place that and the electrical resistance thermometer in a container of water, then compare the two and adjust the resistance of the electrical one to match it.

      • November 14, 2015 5:08 pm

        Thanks. I’ll see if I find any more information.

  10. Green Sand permalink
    November 14, 2015 8:01 pm

    “Why Do Wind Gusts Make Headlines?”

    Because they shut down wind turbines?

  11. John F. Hultquist permalink
    November 15, 2015 4:46 am

    Think of it like your blood pressure. An average isn’t of interest.
    Unless, of course, the average itself is very low or very high.

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