***************************************
Vorticity Advection
***************************************

Vorticity advection is he change in vorticity value over
an area, which is most readily analyzed in the 500mb
Vorticity chart. This chart is available every 12 hrs
on AWDS or AFDIGS.

Vorticity Advection may be positive (associated with upward
vertical motion of air - divergence aloft) negative 
(associated with downward vertical motion of air - convergence
aloft) or neutral, which is a lack of vorticity advection.