In article ,
"Yokel" wrote:

In the absence of ground friction, (which applies very nearly in the free
atmosphere a kilometre or two up or more), the geostrophic wind is a very
close approximation, providing the systems are not moving too quickly or are
developing/decaying rapidly. These circumstances also produce effects not
included in the geostrophic wind calculation.

Another thing to keep in mind is that the Coriolis force increases with
latitude. This means that, even in the complete absence of drag, the
wind cannot follow a closed path (which is what an isobar is), as that
would cause a pressure build-up at some point, which would stop the wind
flowing.

Thus, even neglecting drag, the idea of winds flowing parallel to
isobars is still unrealistic.