You may have noticed this yourself: all the weather apps on your phone report a slightly different maximum temperature. “It’s really going wrong there,” says Maurice Midendorp, a Buienradar meteorologist.

Each app uses a single weather model. For example, Buienradar’s weather forecast is based on Meteoblue, a Swiss weather model. The standard Apple or Google weather app on your phone uses the US GFS weather model, as Middendorp knows. This means global forecasting system.

The best weather forecast

The differences are great. Middendorp: “When I look at the weather models for Tuesday, the US weather model shows a maximum of 43 degrees, while the European weather model (ECMWF) predicts a maximum of 38 degrees. So it just depends on where you look at. But many won’t know weather app users.”

Professionals who explain weather forecasts on radio and television are of course aware of these differences. Or, as Maurice Midendorp explains: “We meteorologists look for the best forecast for the Netherlands in this mix of weather models. My colleague Nikulin did so on Friday morning. She combines her knowledge of the weather with the calculations of that day. A result that deviated from the maximum temperature. in the application”.

exaggerated prediction

For now, Poinradar meteorologists believe that the US weather model is giving an exaggerated forecast for Tuesday. Middendorp: “The GFS calculates the atmosphere and the soil is very dry. If there is a little moisture in the air and the soil, solar radiation can be converted very easily into heat. We estimate the current soil moisture and the atmospheric humidity a little higher, so we think Tuesday will not reach temperature to 43 degrees.

The meteorologist now thinks, on Saturday afternoon, that the maximum temperature will be 39 degrees Celsius on Tuesday in the warmest place in the Netherlands, perhaps only around 40 degrees Celsius. “I conclude that based on all the weather data I take, I would expect it. But it is very difficult to achieve this in a weather app. The perfect weather app does not exist yet. Every day wants to have the best case scenario for the best weather model in your app. So you will have to buy all the Weather models are available, plus you’ll have to choose the best weather model for that moment based on their knowledge by meteorologists. But that’s hard and expensive.”

full of doubts

The gist, according to Midendorp and colleagues from Buenradar: Weather models are full of uncertainties and will remain so for now. “Our computers are not powerful enough to calculate the atmosphere very quickly in detail. In order to make good calculations, we also need to know the entire atmosphere at the moment. And this is difficult, because we do not know every square centimeter. Earth is what the current temperature is.”

This is expected to gradually improve. As a result, weather models will also start to resemble each other more and more. But for now, that’s still the power of meteorologists, who are trying to draw the realistic scenario out of the chaos of those different models.

city ​​vs country

So Buienradar will still be a weather app based on a single weather model for now, but meteorologists are working to integrate the city’s climate into the app. Maurice Midendorp of Buienradar: “We as meteorologists use the temperature of the countryside as a criterion, how hot it is on the grass without trees in the shade. But between concrete and asphalt in the city it is much warmer. In a very hot daytime it can make a difference of 3 degrees And at night it may reach 10 degrees.” In order to determine the temperature of a place as accurately as possible, Buienradar will soon add a few degrees in urban areas.