GrADS bad speed performances

[Ivan Toman]

Hello. I have very strange issue and help is greatly appreciated.

I run WRF-NMM 36-12-4km nesting and after model finishes I forward
output grib1 files to grads (1.9) from all three domains in successive
order. First, 36km domain is processed in GrADS, when it finish 12km
domain comes to work and when it finish, 4km go into GrADS at the end.

My problem is that GrADS has good performance only on 12km domain, on
other domains it is very and extremely slow. These are times for
creating map graphics from these domains:

36km - 40 seconds
12km - 6 seconds
4km - 105 seconds

It is very clear something very strange is going on. Why last domain
gribs files needs almost two minutes to postprocess in GrADS, when
intermediate domain gribs takes only 6 seconds to complete the same job?
Yes, for all three domains is executed completely same .gs script,
domain sizes are almost the same (in number of points), and GrADS don't
output any error or similar unusual messages on any domain. There are no
other CPU jobs that could slow down processing. GrADS use one CPU core
at 100% all of time during this hanging.

These times are for only 6 output gribs (still testing), I need to
extend forecast now to 60 hours, so there will be 10 times more data
than now is, if now GrADS process for 105 seconds then it will work 17.5
minutes to draw all needed maps from 4km domain?? This will become a
serious concern then.

Please, can anybody help me to resolve this problem?

Thanks