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19990913: trajectories with GEMPAK

>From: address@hidden
>Organization: .
>Keywords: 199909132120.PAA07611

>
>Steve,
>
>Thanks for the information you sent me about the trajectory program.
>We have all the executables but for some reason they were never 
>copied to $GEMEXE so I did not know they were there.  Do you think
>the package would work with RUC model analysis?  I would like to 
>try this since I could get an analysis every 3 hours and would not
>have to worry about forecast errors (just analysis errors!)
>
>Donna Tucker                      http://chinook.phsx.ukans.edu/tucker.html
>address@hidden      Department of Physics and Astronomy  
>(785) 864-4738 (new area code!)    University of Kansas                 
>(785) 864-5262 (fax)               Lawrence, KS  66045-2151                   
>  
>


Donna,
The basic program will work for RUC grids, but is currently hardwired
to step through forecast times of a single run rather than multiple
analysis times.

I can modify the program accordingly, as well as the scripts which
currently dump out the model fields for each forecast time and
then the program uses f000 for steps 0-2 hours, f006 for 3-8 hours,
f012 for 9-14 hours etc. Actually, thr program really doesn't 
care about what is in the gdlist output files, but the ETA and
AVN both use a 6 hour time step. To use 3 hourly RUC analyses, the case 
statement in trajectory_gem.c and back_traj.c will have to be
updated to know at what time step to open the next set of grids
for a given model time.

If you will have 3 hourly run analyses (actually you can get hourly 
RUC2 analyses from: ftp://140.90.88.142/ncepe/pggrib) how many runs do you
think you would be using- and are you planning on doing this for 
a particular case or in real time for some last xxx hours?

Steve Chiswell