the sun or a few showers? At the latest when the next change of weather looms, open to the people back their weather Apps. However, while in one application, sunshine is predicted to get in the next heavy rain clouds. Why vary the predictions to be so strong for one and the same place? Why are sometimes call severe weather warnings out, then as the air number?

meteo calculation is enormously complex

to answer that, one must first understand how a weather forecast is produced. Observation stations around the world are permanently recording weather data, the ranges of the wind speed, temperature or amount of precipitation to humidity. All these data are fed into powerful supercomputers that can perform a variety of arithmetic operations per second.

With more data, faster computers and better Algorithms, the results are always precise, writes the Guardian. The air pressure could now be four days in advance so accurately predicted, such as thirty years ago for a One-day prediction was possible.

American Apps inaccurate

in this country is That the Apps show different results, is due to the fact that the provider evaluate the weather data in different ways. The for forecasts in Germany, the most commonly used global weather models are according to the “süddeutsche Zeitung”, the American weather model (GFS), the European weather model (ECMWF) and the German weather model (ICON). None of them is per se superior to the other, each has advantages and disadvantages.

The American data are available for free for anyone, the model is most inaccurate. In the USA, this is not so important here, the weather is often over hundreds of kilometers to a large extent identical, the focus is on the accurate forecasting of cyclones is more likely. This is one of the reasons why the pre-installed weather Apps on Smartphones (and their operating systems are developed in Silicon Valley) for the German market-ideally – the calculations are based on the Europe unsuitable GFS model.

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The German ICON model that offers the German weather service (DWD), is suitable for the landscape of much smaller-scale Germany, and focuses more on the development of fog and ground fog, the “world”. The Grid, which are superimposed on the weather map are in this country only around two kilometers in size, while the American model, it can be ten-fold. In the case of a 20-mile grids, a summer slips through thunderstorm times. The disadvantage: the data of The ICON model costs money.

Some of the App providers, the calculated data give only a dull, others are chasing you through my own Algorithms. Some people is even more reliable, because in parallel on multiple datasets are used, which are guided with the help of its own technologies.

One hundred percent accuracy is not a provider delivers. General weather developments, one could say, three to five days serious before, explain to various experts. If a shower is coming, the day after tomorrow at the campground or not, but to the chagrin of all the festival-goers, not serious predictions. On the Two-week forecasts of some portals, you should not leave anyway, these reflect more General Trends.

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the manufacturer is The best weather App there is not a

But how accurate the predictions are, on average? In the past year, a forecast watch has determined that “” the accuracy of six of the leading, global forecast providers. Were studied the one – to Five-day forecasts for over twelve months for 1145 places. A total of more than 30 million were evaluated to predict.

A clear winner, there was not: Some providers were reliable, what the average temperature or wind speed, the other scored at the lowest temperatures. The MeteoGroup, which is behind the currently in the App Store most successful purchase the App in the “WeatherPro”, was in a British Test, four out of a total of twelve participants.

A Test of the “WDR” saw for Germany in the iOS App “weather XL”, followed by “weather online” and “”. The worst results delivered, of all things, the pre-installed App. You can find more information in this article.

the thing with The probability of rain

But it’s not just the data that make the difference. It’s also about how the results are visualized. Some App is holding back, and shows only a bright sun or raining cloud. Others have several tables available, from which the dew-point, relative humidity, and other data can be read.

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An interesting point, the US statistician Nate Silver, who with the accuracy of his election forecasts for attention. In his 2013 published book “The Signal and the Noise,” writes Silver, some providers specify the rain probabilities are clearly more pessimistic than the weather requires. The reason for this is clear, however: One has to prefer the umbrella and stay dry than to be wet and soggy, while the screen is home. Some providers return to this practice, in the meantime, the back, said, among other things, Peter Neilley, Senior Vice President of the Weather Company, compared to the “Guardian”.

What many do not know: A probability of precipitation of 70 percent means that it will rain on 70% of the day. But only that it is raining with this probability in the observation period at least once – and there were only a few drops. In identifying the providers have access to similar weather patterns from the past, it had not rained in 7 of 10 cases with a similar weather situation. Even in the case of a precipitation probability of 95 percent it can remain dry. Meet the upside-down five percent for a downpour.

Every Smartphone makes the prediction more accurate

The perfect, reliable weather report, it will in the future not to give this Illusion grants Neilley in the conversationäch with the “Guardian”. There are too many parameters that have an influence on the weather. However, the forecasts are more accurate, thanks in part to the user. Or your smartphone. In many models of digital barometers are used to measure the air pressure. The official App of the Weather Channel collects 250 million of air pressure measurements.

this data can be optimised to say, short-term changes, and predicting Rain. Especially in areas with few measurement stations are available, this additional data is worth Gold. Machine-Learning increases the quality of the collected Smartphone data, from 2019, to be included in the official weather forecasts.


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