On Jun 13, 9:21*pm, "David Gartrell"
wrote:
Hi There,

I'm trying to make sense of the GFS 500hPa charts on Wetterzentrale but to
be honest I'm not really sure what I'm looking at. *The High Pressures & low
pressures are easy enough to figure out but what exacly do the colours refer
to. *Assuming they are temperature gradients do they refer to surface
temperatures or something else.

Any advice anyone could give (in layman's terms i'm afraid) would be very
welcome.

Many thanks

David.

The colours refer to contours of the 500 mb surface. They
can be loosely thought of as the isobars at 18,000 ft and show the
circulation at that level. This is obviously influenced to some
extent by the circulation at the surface but is modified in both
position and intensity by the temperature of the column of air between
the surface and the 500 mb level. Thus the 500 mb level will be
higher if the air column is warm or the surface pressure is high.
More useful, in my opinion, are the thickness lines,
which you can get he

http://www.wetter3.de/

This site is considerably more user-friendly than Topkarten but is
less comprehensive in some ways. You still need German, of course.
Mine is rudimentary, which is at least a quantum leap from non-
existent.

The colours here depict the various thickness values. This
is the thickness (in decametres) of the layer from 1000 mb to 500 mb
and is purely proportional to its average absolute temperature. Thus
they show where the atmosphere over a consdierable depth is warm or
cold. Also, Lows tend to move, at least initially, along the
thickness lines.

The 500 mb contours are in black and surface isobars in white.
It can get a bit difficult to read until you're used to it. A bit
like badly-written jazz charts.

Tudor Hughes, Warlingham, Surrey.