Looking at
https://earth.nullschool.net/#curren...8.90,34.75,444 you will see the reason for the turbulence a very strong jet looks like the confluence of two 'jet-streaks' (see
Entrance of Jet Streaks ) click on 'Earth' for the menu and go up and down in HpA levels to see how the jet varies with altitudes and at the 70HpA level the stratosphere is very quiet. Fly above the tropopause if you want a quiet flight.