Surface wind vectors are black line segments with magenta dots for arrow heads.
A 10 m/s wind would span 2 degrees of longitude at the equator. The spacing of
wind vectors is 2 degrees of longitude at the equator. The length of wind vectors
changes with perspective, as if the vectors are painted on the surface of the sphere.
200mb heights are brown. 500mb heights are green.
Maybe also of interest: forecast convergence animation
The nomads server GRIB data source.
NCEP Alert Administrative Messages, check when the data is absent.