David, what is your background and how did you become meteorologist for the French team?
I was a member of the French Olympic Sailing Team in the 470 class for the 1992 Barcelona Olympics and also for the 1996 Atlanta Olympics. I joined the French team in 2008 as meteorologist for the sailing team. Since then, I've followed the team to the Olympic Games in London 2012, Rio 2016 and Tokyo 2020.
What wind conditions will the athletes encounter in Marseille?
The southern harbor is criss-crossed by three main sectors:
-every two weeks, there's a little mistral wind, established at between 15 and 25 knots. Being very warm, it's not very powerful. It is slowed down by natural barriers and has difficulty descending into the southern roadstead.
-Thermal breezes, oriented between south and southwest, originate from the heat exchange between the 35° land and the cooler sea. They represent winds of between 5 and 15 knots.
-Finally, the southeast, which comes from the Earth. It passes over the Marseilleveyre hills, which are between 300 and 500 meters above sea level. Its intensity ranges from 5 to 25 knots, making it very difficult to assess. It's a very opportunistic sector, and if you've got a good read on the water, it can be a real tactical masterstroke.
What will be the conditions for the start of the Olympics?
The first day won't be very windy, with 7-8 knots, close to the west, followed by three days with thermal breezes from the south-southeast. This wind bypasses the relief, with an intensity of 8-15 knots. It rises around 1pm, lasts about 3 hours and then starts to drop.
The end of the week should be more active, with the mistral forecast. This could create some great opportunities for the racers, because paradoxically, the mistral is more complicated to anticipate. It's more random in terms of direction and power.
How do you interact with the athletes?
There's a forecast every morning to describe what they're going to encounter on the water. I keep them informed until 9-10 a.m
Forecasts are 85% reliable, but with thermal phenomena, errors of 4-5 knots can occur. The aim is to provide a scenario, and warn of somewhat unusual site effects
I adapt to each series. We have a very variable population in terms of age among our selectees, with differences in knowledge. I'm there to help them grasp the conditions, and help them develop their ability to read the water as naturally as they would read a book.
