Making Trajectories with data composites

[Jason Snyder]

I have a *.nc data set that is a composite of wind data based on certain
phases of the Madden Julian Oscillation and I was interesting in looking at
the backwards trajectories of air parcels coming from Lake Tahoe in such a
scenario.  I have been trying to work with the script traj.gs, but GrADS
said that TDEF is undefined.  How do I fix this and make a trajectory?

Thanks,

Jason