Formula 1 article published on F1-Only.fr by Célini August 16, 2022. Translated to English

In this summer column, F1only.fr takes you into the heart of the F1 paddock and unveils the backstage of Grand Prix. Today, we delve into weather forecasts. 

 "Will it rain during qualifying or the race?" That's THE question everyone asks before each Grand Prix, and only a handful of specialists can answer it. Indeed, for each event on the calendar, a dedicated team of meteorologists works in the shadows to provide ultra-precise weather forecasts. F1only.fr spoke with one of them, Paul Abeillé, a few weeks ago during the Canadian Grand Prix in Montreal.

Before detailing how these weather forecasts are developed and disseminated, and to fully understand the stakes, let's start with an overview of the atmospheric parameters that influence the behavior of Formula 1 cars. 

Part 1: The Impact of Atmospheric Conditions on F1 Cars

It's no surprise that efficiently driving a Formula 1 car is an extremely complex exercise that requires in-depth knowledge in various scientific fields (mechanics, aerodynamics, electrical, electronics, thermal, computer science, etc.). In addition to these technical areas, F1 cars also face the atmospheric conditions in which they operate, and even the slightest change can lead to significant performance differences. A good understanding of weather parameters becomes a crucial asset to secure a pole position and/or win races. 

Temperature

In all motor sports, and especially in Formula 1, engineers and tacticians closely monitor both the track temperature and the ambient air temperature.

Since the connection between the car and the ground is solely through the contact of the four tires, the power of the power unit is transmitted through them. With the speeds reached by F1 cars, tire friction is considerable, generating a lot of heat, especially in turns. The track temperature (which can exceed 55°C, as was the case at the French Grand Prix a few weeks ago) adds to the equation and becomes a crucial parameter for choosing the right tires. Each type of tire (hard, medium, or soft, designated as C1 to C5) is designed to operate optimally within a narrow temperature range (a few tens of degrees). 

 Table: Optimal temperature range per tire type

A variation of a few degrees in the tire tread temperature compared to the optimal operating window can cost up to a tenth of a second per lap! Enough to lose several positions during qualifying.

The complexity, therefore, lies in staying in the ideal temperature range for as long as possible, i.e., the one that provides the best grip. Using the tires below the target range does not generate enough mechanical grip, while using them above leads to overheating, accelerates degradation, and inevitably results in a sudden drop in performance (or even a puncture).

Another challenge is that since the front and rear tires do not operate exactly in the same temperature ranges (they also have different widths: 270 mm at the front versus 405 mm at the rear), a change in the asphalt temperature (caused, for example, by a clearing or a cloud passage) will increase or decrease the grip level of these tires unevenly. To minimize these differences between the front and rear axles, mechanics will adjust the settings of the car (for example, by adjusting the downforce on the wings). Drivers can also vary tire temperature by adopting a suitable driving style: if they want warmer tires, they will opt for more aggressive driving, especially in high-speed turns. Conversely, if they want to cool the tires, they will have to reduce their speed in these same turns. Finally, they can also adjust the differential (which changes the torque of the rear wheels) or change the braking distribution between the front and rear of the car.

Throughout the practice sessions, the temperature of the tire treads is monitored and continuously scrutinized thanks to tiny infrared cameras installed on the wings or in the mirrors. The generated thermal images are then transmitted to the pit, allowing real-time monitoring of the temperature of the surface of each of the four tires to adopt the best settings and choose the best strategies.

 Two infrared cameras installed on the front wing of the 2022 Mercedes.

While the behavior of the tires is influenced by the track temperature, the cooling of the power unit (engine), brakes, and all other components of the car is directly related to the ambient air temperature. This is why teams constantly monitor not only the ambient air temperature but also the temperature of various components of the car. The hotter the ambient air, the more the airflow circulating along the bodywork needs to be diverted and sent into the component to be cooled, thus keeping it in the ideal temperature range. In hot weather, aerodynamicists will open the bodywork vents to increase the airflow to the radiators to avoid overheating. On the downside, this operation results in a waste of airflow and generates higher air resistance (drag) at the expense of aerodynamic performance. Finding the right compromise is difficult but remains the key to achieving the fastest lap time possible. The same process applies to brakes, so the size of the air intakes is sized accordingly. 

Wind Direction and Speed

Engineers have long understood that the performance of Formula 1 cars is also linked to wind speed and direction. While weak winds may not seem to pose a particular problem, strong winds and gusts (especially in long straightaways and fast turns) will affect the balance of the car and thus its maneuverability. Max Verstappen and Carlos Sainz painfully experienced this during the Spanish Grand Prix in 2022 when both went off track at turn 4 of the Catalunya circuit due to gusts. 

In absolute terms, the goal for engineers is to develop a car that generates the most downforce and the least drag possible. However, this task is complicated by the simple fact that increasing downforce also increases drag. It should be noted that downforce is proportional to the square of the relative speed. That's why seemingly weak wind can make a significant difference. If we take an F1 car traveling at 320 km/h and add a headwind of 20 km/h, we have an increase in relative speed of 6.7%, but an increase in downforce of 13.8%, which is a significant difference! The same phenomenon occurs, but in the opposite direction, with a tailwind. In summary, if the wind blows from the front, the wind speed adds to that of the car (increase in relative speed) and an increase in downforce. In contrast, if the wind blows from behind, the relative speed of the car is lower, and it generates less downforce.

Atmospheric Pressure

The variation in atmospheric pressure over a weekend has little influence on the operation of a Formula 1 car. However, for circuits located at altitude, such as Mexico (2600 meters above sea level) or, to a lesser extent, Austria (700 meters), the performance of atmospheric engines is modified mainly due to the amount of oxygen the turbocharger has to digest. At altitude, the turbo must spin at a higher speed to compress the less dense air, which reduces engine performance. To compensate for this loss, the teams adapt the turbocharging settings (variable geometry turbos) and the amount of fuel injected into the combustion chamber.

The Rain

Even if less than 10% of F1 races take place on wet tracks, driving at over 200 km/h under these conditions is a remarkable feat. Although there are tires specifically designed to disperse a large amount of water (Full Wet tires evacuate more than 80 liters per second!), grip on a soaked track remains very precarious. Additionally, visibility becomes nearly zero due to water spray, making it potentially very dangerous. In extreme cases, it leads to the deployment of the safety car or the complete stoppage of the race (red flag) or a delay in the start, as was the case in Monaco last spring.

When it's raining or about to rain, knowing precisely and as far in advance as possible the evolution of conditions is decisive. Anticipating a pit stop at the very beginning of precipitation can be extremely rewarding if the rain intensifies. Similarly, when precipitation stops, the track evolves quickly, and a less wet racing line gradually emerges. The challenge for teams is that the entire track does not evolve in the same way, and there are always sectors that dry more or less rapidly. The stakes and the difficulty lie in determining the opportune moment to switch to more suitable tires to gain positions. This is when a cat-and-mouse game unfolds within the teams. The willingness to take risks is often inversely proportional to the position occupied by the drivers in the race. In this specific case, the further back a driver is in the pack, the more tempted their team will be to switch to dry tires to try to move up in the standings. Tacticians rely on ultra-precise weather forecasts to make decisions. The on-track duel partially shifts to the pits, making races on wet surfaces even more intense and thrilling.

Now that we have seen the effects of atmospheric conditions on the behavior of F1 cars, we understand the interest and advantage of being able to predict precisely the state of the atmosphere when the cars are on the track. Welcome to the exciting world of weather forecasts.

Part 2: Weather Forecasting in Formula 1

In the quest to bring the best car and, above all, be prepared to adapt to weather conditions, teams meticulously prepare for each race several weeks before the deadline, and part of this preparation includes a weather component. To initiate this process, meteorological data from previous editions is analyzed, and teams start paying attention to weather forecasts about a week before the event. It is precisely during this preparatory phase and throughout the Grand Prix weekends that Météo France comes into play. Interview with Paul Abeillé, one of the forecasters-advisors, met with Roman De Lauw, communication manager at the FIA, a few weeks ago in the Montreal paddock.

Météo France and Formula 1... a long history

For many international sporting events such as Roland Garros, Wimbledon, the Tour de France, and motorsports like WEC, the 24 Hours of Le Mans, and F1, it is essential to have the most accurate and timely weather forecasts possible. This is exactly the niche of Météo France Sports, the commercial branch of Météo France dedicated to sports events.

Thanks to its expertise in this field, the French public institution has a multi-year contract with the FIA to provide detailed weather reports and forecasts for each F1 Grand Prix. Paul adds, "Forecasters and technicians from Météo France Sport are specially trained for high-level sports, and the services offered are adapted according to the stakes and regulations of each sport." As part of his duties, he mentions that he has also covered other international competitions such as the World Rowing Championships and paragliding championships.

Tools and steps for forecasting a F1 race weekend

When asked about the major steps in developing forecasts for an F1 weekend, the meteorologist responds, "The process begins about ten days before the Grand Prix with a comprehensive analysis of atmospheric conditions. The forecaster in charge of the upcoming race then identifies the air masses present, the circuit's topography, and outlines an initial trend for the long term. On the Monday preceding the race, the three-person team is on-site, and an initial forecast is formulated and released. This forecast will be refined regularly in the following days with an increasingly high frequency, up until the Sunday race."

The specialist explains that rain is a very specific challenge in Formula 1. Therefore, it is essential to establish precipitation weather forecasts with ultimate precision (on the order of minutes). To enable the creation of such precise forecasts, Paul informs us that he has access to a tool specially developed by Météo France: a high-definition mobile weather radar. "This radar, which travels with the F1 freight throughout the season, is installed at a height near the circuit (often on the roof of a hotel) a few days before the race by the team's technicians. This radar, with a resolution on the order of 100 meters, can detect even the slightest precipitation with very high precision within a radius of 20 to 30 km around the circuit and up to 80 km for heavy rains. The data processing part of the information provided by this radar is also developed by Météo France Sports, and a new map is generated every minute with a processing time of about 35 seconds! Almost real-time."

Map of precipitation generated by the high-resolution mobile weather radar

"For Formula 1, our job is to create and disseminate weather forecasts so localized that they could apply to people's gardens!" Paul Abeillé, forecasters-advisors at Météo France Sport.

Among other tools available to the forecaster, there is access to data from three weather stations specially installed at the ends of the circuit and various numerical models. Paul mentions having access to about a hundred weather models, including deterministic and ensemble models. Deterministic models are generally used up to three days in advance and present a single scenario. Ensemble models are used for forecasts beyond three days and present several possible scenarios (up to 50!). Each weather model is refreshed several times a day, and the forecaster's job is to select the most realistic scenario among those offered and avoid surprises. This is a challenging exercise that requires excellent knowledge of meteorology, aerology, and a lot of on-the-field experience. Our interlocutor sums it up, "Our job is to create and disseminate weather forecasts so localized that they could apply to people's gardens!" and adds, "The difficulty is to send the right message at the right time, and the person receiving it must be able to understand it."

Starting from Thursday, forecasts are adjusted and made hourly (or in blocks of 3 hours) and are available until the Sunday race with special attention to each of the practice sessions (namely the three free practice sessions, qualifying, and, of course, the race). When the cars are on the track and there is a risk of rain or thunderstorms, forecasts are available every minute, indicating the start and end time, as well as the intensity and type of precipitation.

Who are the forecasts intended for?

Paul explains that Météo France's weather data and forecasts are intended for the FIA to organize the event (for example, to ensure the safety of the public, personnel, and facilities in case of weather alerts) and also for the ten teams on the grid. "Each team has exactly the same information, and the dissemination is done through a web portal and via radio briefing or in person if necessary. On this portal, the FIA and the teams have access, for each race, to all relevant information, including the type of climate, the history of atmospheric conditions in recent editions, real-time weather data provided by the three weather stations installed on the circuit, specific messages, forecasts on various parameters, and, of course, the precipitation map provided by the high-resolution weather radar." These are the images that television broadcasts when rain appears from the pit wall.

Neutrality and good communication

When F1 cars hit the track, the forecaster and the two technicians (one who monitors the radar and the other who supervises the technical functioning of the entire solution from the paddock) are on hand to adjust weather forecasts if needed. In case of major changes in atmospheric conditions, the weather team, which is in constant contact with the race director, communicates the expected condition changes for the next few minutes. The meteorologist's role in this environment is to communicate information as neutrally as possible and must not influence the race director's decisions in any way. "Everyone has their own job!" as Mr. Abeillé mentions. Decisions are made based on this information. The stress level is, of course, related to weather conditions, and all involved parties are well aware of the consequences that changes in atmospheric conditions can have on both strategy and safety. Good understanding and, above all, very good communication are then essential.

What data is provided in the weather forecasts?

To this question, Paul responds, "For each forecast, the Météo France Sports team provides the following parameters: sky condition, precipitation risk (expressed in percentage), wind direction and speed (including gusts), atmospheric pressure, humidity, air temperature, but also the track surface temperature. For this last parameter, Météo France installs an infrared sensor on the pit lane and performs manual calibration based on the color of the pavement (darker asphalt absorbs more heat than a lighter surface)." As we saw earlier, the track temperature can exceed 50 degrees and strongly influence tire degradation! Is wind important? "Yes, wind speed and direction are also very important because these data can influence the downforce level and sometimes even lead to the use of certain aerodynamic kits more suitable for these conditions."

At the end of our interview, we learn that Météo France also provides certain weather data such as air temperature, track temperature, atmospheric pressure, wind direction, and wind speed on the live timing page. This page is accessible and available to the media as well as the general public, and this information can also be viewed in the Formula 1 application and on the corresponding website. 

Experience feedback and feedback

Among the anecdotes, there is, of course, the super Typhoon Hagibis during the 2019 Japanese Grand Prix, which forced the postponement of qualifications to Sunday. More recently, the 2021 Belgian Grand Prix had to be stopped, and this year, the stormy situation that developed just before the start of the Monaco Grand Prix. "Yes, in this specific case, that's exactly what happened; the reactivation of the storm cell above the Principality was very difficult to anticipate and required a continuous reassessment of the situation. A spicy moment!" as the meteorologist points out, with a slight smile. 

On an annual basis and with the aim of improving the meteorological forecasting service, a briefing is organized to gather feedback from the FIA and the teams. This feedback continues through email exchanges. So the next time you see changing or particular weather conditions during a Grand Prix, you will better understand the stakes and all the work happening behind the scenes. By the way, what will the weather be like for the Belgian Grand Prix? 

Special thanks to Mr. Paul Abeillé from Météo France and Mr. Roman De Lauw from the FIA for making this interview possible.