It is an interesting exercise to try drawing a small scale (say
1:1,000,000) chart on these occasions. I have found that the only sensible
drawing of the isobars is to make them discontinuous at the cold front. Do
that and you can make sense of otherwise apparently anomalous wind
directions immediately in the cold air.

Since line convection comes with a near vertical airmass discontinuity,
there is no logical reason why there should not be other discontinuities
along the line.


I thought cold fronts, and sometimes warm fronts for that matter, were
normally drawn with a discontinuity in the isobars anyway. Trying to make the
isobars "rounded" frequently doesn't work because in many cases there is no
flow *through* a front, at least at the surface.

Tudor Hughes, Warlingham, Surrey.

TudorHgh wrote:

It is an interesting exercise to try drawing a small scale (say
1:1,000,000) chart on these occasions. I have found that the only sensible
drawing of the isobars is to make them discontinuous at the cold front. Do
that and you can make sense of otherwise apparently anomalous wind
directions immediately in the cold air.

Since line convection comes with a near vertical airmass discontinuity,
there is no logical reason why there should not be other discontinuities
along the line.


I thought cold fronts, and sometimes warm fronts for that matter,
were
normally drawn with a discontinuity in the isobars anyway. Trying to make
the isobars "rounded" frequently doesn't work because in many cases there
is no flow *through* a front, at least at the surface.


But a line with a kink is still continuous. I think what Rodney is
advocating is drawing pressure lines up to the front from the warm side and
repeating it from the cold side without worrying about whether same-value
isobars meet on the front.

Graham