Wind speed big difference between now and forecast

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1

I’ve got a chat showing the current wind speed and the forecast. The forecast is a lot smaller than current and then each hour when the firecast becomes the present, you can see the forecast was well out.

If I look at the data:

temperature: 16.1
humidity: 36
pressure: 1021
wind_bearing: 150
wind_speed: 9.25
attribution: Data provided by OpenWeatherMap
forecast:
  - datetime: '2021-04-19T11:00:00+00:00'
    precipitation: 0
    precipitation_probability: 0
    pressure: 1021
    wind_speed: 2.69
    wind_bearing: 154
    condition: sunny
    temperature: 15.5
  - datetime: '2021-04-19T12:00:00+00:00'
    precipitation: 0
    precipitation_probability: 0
    pressure: 1021
    wind_speed: 2.83
    wind_bearing: 159
    condition: sunny
    temperature: 16.1
  - datetime: '2021-04-19T13:00:00+00:00'
    precipitation: 0
    precipitation_probability: 0
    pressure: 1021
    wind_speed: 3.07
    wind_bearing: 162
    condition: sunny
    temperature: 15.8
  - datetime: '2021-04-19T14:00:00+00:00'
    precipitation: 0
    precipitation_probability: 0
    pressure: 1021
    wind_speed: 3.32
    wind_bearing: 165
    condition: sunny
    temperature: 15.6
  - datetime: '2021-04-19T15:00:00+00:00'
    precipitation: 0
    precipitation_probability: 0
    pressure: 1020
    wind_speed: 3.42
    wind_bearing: 165
    condition: sunny
    temperature: 15.3

You can see it’s almost like the current wind speed and forecast are measured in different metrics.

2

Forecasts predict the expected average wind speed for a period of time over a given area. The instantaneous real value can vary by a considerable amount over that time within the area. From 0 to 40% above the average for my local forecaster.

Wind speeds are predicted at a particular height and a particular grid resolution. For my service, 10m above mean sea level in a 10km grid for today and tomorrow, and a 55km grid for the following 4 days. Within those grid areas local conditions can dominate the averages. Winds being funnelled between or shaded by buildings or hills for example.

So…

What height is your now measurement being taken?

What height are the predictions for?

What grid area is the predicted average over?

Do you have any structures that will affect local conditions?

3

Thanks Tom

I’m afraid I don’t have the answer to any of those questions, all the data is pulled direct from the OpenWeather integration, I’m not sure how they measure the data points.

You may be right to be fair, I just would have thought the metrics they would have used for now and predicted would have remained the same.

4

Oh I thought you were measuring the “now” locally with a weather station.

Well if both data comes from the same source, I guess you should find out where their “now” measurements are being made.