I have no doubt that there is an explanation for the drift but the problem is that the subject is extremely complex and very few if any understand the forces involved.
Many moons ago I was sat in Tom Crean’s pub, the South Pole in, he of Shackletons expedition, having a discussion with a meteorologist who lectured on the world circuit. He obviously knew the theories of wave propagation but not the realities.
50 years ago I was taught to forecast from station reports, draw synoptic charts and predict the weather around the globe; I soon found out that theoretical weather is not local weather. I asked our aerodynamicist how a two channel model could perform an axial roll on rudder alone; reply with high Reynolds number aerodynamics does strange things.
From there I’ve re learnt aerodynamics and aerology from gliding and again with paragliding with combined 4000 plus hours. The atmosphere does stuff that the textbooks do not cover..there is now upwind influence, wave flow from wind shear associated with temperature inversion and interference patterns to name a few.
Morning flights in Ballons are generally influenced by temperature inversions, shear associated with them and wave.
I tried flying a drone with an anemometer to measure this phenomena before I paraglide having been caught out. Balloonists release toy helium balloons to obtain an approximation of the conditions.
We have come a long way from my first glider which did the first 300km uk flight where the designers got the wing, brakes and rudder wrong; we now have a world record of over 3,000km and paragliders have gone from 5 km to 600 plus. Catamarans have gone to incredible speeds as have model gliders at over 300kph in ridge lift using wind shear. A spin off of these back shed technology is wing tip design.