Windspeed and direction different heights

[danie]

I am not too sure how to use the wind direction/speed at different altitudes. Say for instance you take a location that is 5000' amsl and use the cursor to move the height to 6400 feet....does it mean that the altitude is 6400 feet above the 5000' elevation or does it mean 6400 feet amsl, in other words 1400 feet above ground (the 5000' location)?

[meteo GR]

@danie
the winds aloft are amsl.
Actually (and more precisely) are the winds on standard isobaric surfaces.
For example the wind at 5000ft is actually the wind in a "surface" of the atmosphere where the pressure is 850 hPa.

Over mountains those "isobaric surfaces" may intersect* (cut) the orography (land surface).
Thus, if you point on Everest and chose wind at diferent altitudes you'll find out that wind "stays the same" at all the levels from Om (msl) up to 8.000m.
On the airgram you'll see no wind at low levels.

• Actually, models isobaric surfaces "touch" models land surface.

Hope the following image will help.