Rocky Stevens wrote in news:df844305-ac37-4d08-
:

BTW, if anyone else would like to weigh in with a serious answer, I
would appreciate it. I can sort of see how they could use radar to
determine clound coverage, but the winds aloft thing is really
puzzling me. Take a look at http://www.navmonster.com/wx/KCDW-25; just
one Pirep (which does not even include winds aloft) but they have
winds aloft for various altitudes.


They do it primarily from the pressure gradient. The steeper the gradient
the stronger the wind.

Actually, measuring between the isobars along your route regardless of the
angle they may form in relation to it, only counting the frequency, will
give you a very good idea of your head or tail and crosswind.

There's a scale on some types of detailed surface charts that directly give
the geostrophic wind speed based solely on isobar seperation.

Bertie