Why turbulent air is uncomfortable to fly in.
The weather has been remarkably good the first two and a half days of the race, considering the forecasts. Two weather phenomena were predicted to influence flying conditions considerably: föhn winds and thunderstorms.
Up until this afternoon, both have been mild. The athletes have had some considerable wind to deal with but with great skill they all managed to stay safe in the air and on the ground.
Today, the race might be influenced by these phenomena a lot more than the athletes would like.
Föhn winds are very strong winds at higher altitude, either from the north or the south in the Alps. This wind then hits the mountains and rolls down at high speed like a waterfall, causing severe turbulence in the air. This makes flying dangerous for pilots of any aircraft, and particularly light ones such as paragliders.
Thunderstorms are dangerous for a number of reasons. Flying in rain makes a paraglider very difficult to control. Cumulus congestus, as the large thunderclouds are called, can create very strong updrafts that can even suck pilots up and only release them at dangerously high altitudes of over 8000m or higher. Additionally there is the danger of lightning striking.
But the first thing the athletes notice on the ground or in the air are strong winds, called gust fronts. The air is pushed out ahead of the storm creating dangerous wind gusts of up to 60km/h or more.
On the ground, winds are strong in Lermoos, showing the power of the upcoming thunderstorms. Paul Guschlbauer (AUT1) said that it is uncomfortably turbulent in the air.
When paragliders fly in turbulent air, their gliders move around a lot. They become difficult to control. The canopy must stay open and overhead as much as possible. If it doesn't, it looses its shape as a wing and therefore stops flying.
Paraglider wings can absorb a lot of turbulence, because they are flexible and can easily collapse partly and reopen again. This absorbs the energy of the turbulent air around it. But for the pilot, this means he has to use the controls a lot to ensure it doesn't stop flying. This requires great skill and concentration - hence Paul's comment that the turbulence is uncomfortable.
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