Err I ride jetstreams for a living
they don't affect TAS just the Groundspeed.
Whether I am in the jetstream or not the Mach number and or IAS and the TAS are the same, the Groundspeed changes though. If i was in the centre of a jetsream and performed a 180degree turn all that changes is groundspeed, IAS/TAS and Mach number remain the same.
Have a look here :
http://en.wikipedia.org/wiki/True_airspeed
and here:
http://en.wikipedia.org/wiki/Ground_speed