Soyuz descent module re-entry flight is piloted (one of two modes AUS/computer or RUS/manual), using 8 thrusters, toward the Kazakhstan landing site. The ballistic re-entry occurs only when the other modes are inoperative (e.g. TMA-11) or in case of an urgent departure from the ISS.
With a controlled descent, the actual landing location should be equally distributed around the target point, but it seems most of the landings occur N or NE of it.
Typical flight path of the re-entering spacecraft:
As pointed out by TildalWave, the winds may cause the module to drift after the parachute is deployed. From the re-entry profile described at SpaceFlight-101:
At an altitude of about 9 Kilometers, the Pilot Chute opens and deploys the Drogue Chute that slows the vehicle from 240 meters per second to 90m/s. At an altitude of 7.5 Kilometers, the Main Chute is opened and slows the vehicle down to 6 meters per second. While flying under the main chute, the Soyuz transitions from a nearly horizontal flight to a vertical descent.
This gives about 8 kms of trajectory at low vertical speed (12 kts / 22 km/h) and high drag configuration where the module may drift. About the wind, as researched by Rikki-Tikki-Tavi, the prevailing wind blows to NE in Kazakhstan. The wind blows most of the time to NE and E, according to WeatherSpark for Kyzylorda Airport WX station:
At first sight, a correlation is possible. Buy why would the Russian Federal Space Agency ignore wind in the flight planning? Maybe this is their reasonning:
- The aircraft departure form the ISS is possible only when the wind is within given acceptable criteria which guarantee a drift cannot push the spacecraft outside a predefined safe area.
- A return schedule and flight path is computed without wind and published.
- Soyuz is deorbited according to this schedule.
- Some drift occurs due to the actual wind, the rescue team follows.
There are other possible explanations, e.g. this one:
- A delay occurs in the re-entry schedule.
- The predicted landing location is adjusted, but not shared with the public.
- The landing actually occurs at the adjusted location, but we don't know.
Neither of these scenario is really satisfactory. Is it possible to shed light on the way the re-entry path is managed, and whether the wind is taken into account?