yeah, sub tropopause all our weather exists below the tropopause. It doesn't alter the gulfstream, that's a nonsense though it can be affected by cooling water temperatures but in this case it's not, just normal seasonal cooling.
Yes the jet is swooping south mid atlantic but that's what its supposed to do at this time of year as the Azores High sink south the polar airmasses sink also.... this is what winter is supposed to be like.... just our illustrious journalists and hack "Experts" like that clown Corbyn and his cronies will always hype a story purely to suck the British people into a panic.... this cold is normal!!