National meteorological services follow 3 main stages in establishing weather forecasts
Weather forecasting can only be done in 3 basic steps according to the reference meteorological institute in the UK. The first step in predicting a weather forecast is, therefore, observation, using satellites, sensors, and radar.
Then we move on to simulating the evolution of the atmosphere using numerical models with a great deal of technology, which only national meteorological services have.
Finally, meteorologists have to analyse the results of the weather forecast and then send the weather information to all media (internet, connected devices, media, etc.).
Step 1: Collection, observation, and assimilation of meteorological data
As you can imagine, observation is the very first step, but above all the key step, in making a good weather forecast. It is a phrase that combines the collection of observations on the ground, at sea, in the atmosphere, and even in space.
The aim is simple: before making forecasts and looking at the future, we need to understand the present: the state of the atmosphere, the surface ocean, and the snow cover.
Once this collection has been done well, the weather and climate work can begin. The data is then transferred, disseminated, and exploited using extremely powerful information systems.
A titanic network and infrastructure
National meteorological services invest heavily in its observation network and essential infrastructure, without it, nothing would be possible and weather forecasts would not progress.
Regarding the devices for measuring and collecting weather data, the British meteorological service uses:
- Numerous satellites that provide valuable and varied data in real-time
- From networks of ground ground-based measurement stations
- Buoys placed at sea
- Radio soundings
- Various sensors onboard airliners (the AMDAR system) as well as ships
- From hydrometeorological radars (also called weather radars or precipitation radars).
For this first stage, meteorological services use weather satellites (90%) and radiosondes, sensors, and data from other services (10%).
Assimilation of collected data
The next phase, the assimilation of the collected weather information, consists in separating extra information to retain only the useful data from a meteorological point of view. This is a key step considering that every day, no less than 22 million observation data are used by the models after the assimilation step.
Of course, the more data is collected, the more accurate the calculations are… but processing them requires phenomenal power.
But let's move on to the simulation using models.
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Step 2: Simulation of the evolution of the atmosphere
It is then the highly sophisticated numerical models of national meteorological services that simulate the evolution of the atmosphere according to all the observation data. These are nothing less than the physical laws that are used to govern the atmospheric evolution and thus establish realistic weather forecasts.
These include the laws of fluid mechanics, the laws of water state changes (condensation, evaporation, and precipitation course), but also radiation, turbulence as well as interactions with the earth's surface and space.
Each weather forecast is therefore based on a model, from which weather simulations are derived. To do this, national meteorological services currently use 2 supercomputers to efficiently carry out the billions of calculations required to solve the simplified mathematical equations from which the atmospheric evolution forecasts are derived. The peak computing power of these supercomputers is now more than 5 Petaflops… which is just gigantic.
After all, that's what it takes to make a model possible and to forecast the weather the way the pros do it!
But to create weather data that the public can understand and to obtain clear forecasts, we need to go further than simulation: this is the work of meteorologists.
The Netatmo Smart Weather Station gives you access to all your ultra-localized weather information directly on your smartphone. The sensors are in your house, the outdoor module is right in front or behind the house and the data is always with you. The weather has never been so easy to access.
Step 3: Meteorologists analyse model simulations
The information provided by models and supercomputers is not weather information: these data are meaningless for forecasting the weather. These are the meteorologists, who, thanks to their expertise, can analyse the complex results provided to derive concrete information on the weather forecast.
They have different scenarios at their service and it is up to them to choose the most likely one. These are the so-called "forecast products" which are translated into weather maps and forecasts: you know that!
The weather data is then digestible for the general public. The work of national meteorological services is to make weather data accessible is therefore enormous.
As you can see, the reason why your national meteorological service provides such accurate weather data and forecasts is because of the enormous amount of work that goes into it. Its resources are immense, and for good reason: collecting weather data and extracting forecasts requires a lot of infrastructure, equipment, and resources.