The 400K T+72 from ECMWF looks really weird, not what I would expect to see. Are
there any dynamical climatologists looking in here who would care to comment on
the present situation ?

Will.
Unfortunately the forecasts are unavailable ATM but the analyses are good
ETA model tropopause forecasts to T+48 are at-
http://zephyr.meteo.mcgill.ca/gary/etatrop.html
for AVN to T+168 see-
http://www.atmos.albany.edu/student/mjd/maproom.html

http://met.psu.edu/tropical/tcgengifs/
has AVN PV products ,not polar projection.UKMO products seem curtailed here tho,

--Ive no expertise in these matters but it seems clear the arctic vortex is weak and warm
ATM,leading to negative indices of the annular mode,blocking etc.
regards,
david