Open the dashboard

For teachers · Worksheet 1 of 5

How a forecast is made

Nobody “guesses” the weather: we measure what the atmosphere is like now and calculate, with physics and computers, how it will change. In this worksheet we follow that path with the METEO / Atlas dashboard.

Aim

To tell an observation (what is measured) from a forecast (what is calculated), learn the steps of a forecast and understand why it always comes with some uncertainty.

  1. ObserveStations, radar, satellites and weather balloons measure the atmosphere.
  2. CalculateNumerical models solve the equations of the air and move the weather forward step by step.
  3. Combine and explainSeveral models are compared and we say how far we can trust them.

Activity

  1. 5 min
    Brainstorm. How does anyone know what the weather will be like tomorrow? Write the ideas on the board: we will go back over them at the end.
  2. 10 min
    The simple view. Open the dashboard at the school's location. Read the maximum, the minimum and the rain, which appears as “X in 10 scenarios”. Look at the bottom to find which data it all comes from.
    Open the simple view
  3. 10 min
    The models, one by one. Switch to the Enthusiast view and look at the “Multi-model meteogram”: each line is a different model. At what point do they spread apart the most?
    Open the Enthusiast view
  4. 5 min
    Wrap-up. Go back to the ideas from the beginning and sort them into the three steps above: observe, calculate, combine and explain.

Questions

  1. What is the difference between an observation and a forecast? Find an example of each on the dashboard.
  2. Why does the dashboard use six models instead of just one?
  3. If the dashboard says “7 in 10 scenarios with rain”, is it certain to rain? Explain it in your own words.
  4. In the meteogram, are the models more alike over the next few hours or three or four days ahead? Why do you think that happens?
  5. If there is a thunderstorm warning, who should you listen to?

Answers for teachers
  1. An observation is a measurement of what is happening: the temperature at a station, the rain the radar sees. A forecast is a calculation of what will happen: tomorrow's maximum or this afternoon's rain.
  2. Each model simplifies the atmosphere in its own way (grid size, how it calculates clouds or the ground). The median of several is usually more accurate than any one of them on its own, and if they disagree we know there is more uncertainty.
  3. No. The European centre (ECMWF) repeats its forecast 51 times with slightly different starting conditions: if it rains in 7 out of 10, the probability is 70 %. It might not rain.
  4. They are more alike at the beginning. Small errors in the starting point grow over time: the atmosphere is a chaotic system. You will see it in worksheet 2.
  5. The official warnings from AEMET and Civil Protection. METEO / Atlas calculates guide forecasts and is not an official service.