Curse of the Jet Stream

[gb_astro]

Just the last couple of months I have realised the
importance the Jet Stream (JS) has on astro viewing.

Looking at the JS maps over this time one obvious feature
seems to be the fact that the most of Australia is usually
in the firing line most of the time.

Can anyone advise how the JS usually behaves over a longer period?
Does it move north or south enough to miss Australia or do the wind speeds
slow enough not to be a problem?

Thanks,
gb.