"Mike Tullett" wrote :

I agree about the low, Jon. Warmer air was sucked in to it when it was
near Iceland. I recall, many years ago, there was a debate on just
important baroclinic factors were in the development of polar lows. But
it's a long time since I read the literature on the subject.

I think I remember the same literature, Mike. There were a lot
of mesoscale features in the 1960s which were lumped together
under the generic title "polar low", and they spawned a lot of
papers in the meteorological journals. Browning and Harrold
in QJ rings in about 1967 rings a bell (when I could actually
understand most [well, some] of the papers in QJ!)

Some of these features could be traced to lee vortices
south of Iceland (in a N-ly), some to vortex-shedding
from the Norwegian lee trough (in a NE-ly), and some
to shallow quasi-baroclinic disturbances developing in Denmark
Strait marking the boundary between Greenland air and
peripheral Atlantic air (which these days would be recognised
by contrasting theta-w characteristics). My memory is that
pseudo-frontal boundaries were often evident at the 700 mbar
level, but rarely at 500mbar, and that the pseudo-cold front
was almost invariably much more clearly defined than the
pseudo-warm front.

Philip