well, tornadus can be tough to catch. You should either use ultra balls, or wait until night then use dusk balls. If you threw 20 or more and still can't catch it, then restart and try again. I would suggest putting it to sleep or paralyzing it.
Tornadus is probably the best candidate for your Master Ball. Because it is a roaming Pokemon which can flee from battle, it's worth it for that assured capture. While it may not be as strong as Kyurem, Kyurem can nonetheless be captured the usual way with a bit of patience.
Yes
Just be paitent and catch it with a pokeball!
you cant catch it you have to get it from a friend that has Pokemon black or get from a gts tradeYou can't the only way to get Tornadus in Pokemon White is by using cheats or by trading it from Pokemon Black.
MasterBall
You catch Cobalion with any Pokeball that is possible to catch it in.
throw a pokeball at it
A lure ball :)
you can only get tornadus in black or you can trade.
a quick ball or a master ball
GS ball
The Master Ball is the strongest Pokeball as it guarantees a catch without fail when used on a wild Pokemon.
Tornadus is probably the best candidate for your Master Ball. Because it is a roaming Pokemon which can flee from battle, it's worth it for that assured capture. While it may not be as strong as Kyurem, Kyurem can nonetheless be captured the usual way with a bit of patience.
Yes
a pokeball
Tornadus is a roaming Pokemon that does not stay in one place.
I recommend the master ball