"Martin Rowley" wrote in
message ...


... yes, it certainly is marked. All I can come up with atm is
that the
00Z Watnall ascent (can't see the 12Z yet) which was in the warm
air at
that time, *would* produce deep moist instability to the surface
temperature/dew point regime just ahead of the surface cold
front - i.e.
Air temp ~19, dew point ~16 or 17. The key would be the surface
temp
getting high enough as the AS thinned behind the upper cold (as
Jon
noted above), allowing surface-based convection to be initiated
and
'focussed' ahead of a PVA-maxima swinging around the upper trough
(which
seems broad on the low-res charts I have available - so it will
almost
certainly contain minor lobes of +ve vorticity) to both help
initiation
and force the resultant convective elements to run 'in the flow'.
The
thing we have here that _perhaps_ is not always present is the
lobe of
notably high surface dew points that has been advected ENE'wards
(as
noted in another thread).

What might have been the impact of convection cells reaching the
moist layer (i.e. the frontal surface), say somewhere between 600
and
700 mbar?

pe