Doha to New York is about 10,770 km and usually takes around 15h in the air. The track it follows runs over the Middle East, the Anatolian plateau, the Black Sea, the Eastern European plains, Central Europe, the North Sea, the British Isles, and the North Atlantic.
Air lifting over the Anatolian plateau can raise brief, light ripples at cruise; crews know these spots well and the movement stays gentle. Over the Black Sea, the North Sea, the Eastern European plains, and Central Europe the air is usually calm and settled. Above the Middle East daytime heat can stir shallow thermals lower down, but the air smooths out at cruise. Nearer the British Isles and the North Atlantic the weather turns more Atlantic and the ride can be livelier for short spells, still firmly within the routine. This track threads jet-stream latitudes, so in winter you may feel a few minutes of light, choppy air high up; summer usually rides calmer.
A flight this long spends hours at a high, smooth cruise. Even when one stretch is bumpy it is a small slice of the whole trip, and the aircraft treats it as routine.