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GARP grid navigation "feature"

Hi --

We discovered a potential bug in GARP having to do with the gridded data and 
navigating it to maps.

We had been blowing up the RUC 850 wind field to better compare the forecast 
with our current pibal obs.  (I later find out the problem occurs with other 
models as well.)

Try the following.  Bring up GARP and select a RUC mode to plot under the 
"model plan projection" icon.  Select, for example, an 850mb wind field.  Once 
the field is populated move the cursor to be centered exactly over the 
4-corners and while holding down the mouse button, drag the mouse to just cover 
New Mexico.   The zoomed field should now have the county lines in it.  Note 
where the grid points are with respect to the geographical county line 
features.  -- Just pick one that is close to an obvious location.   Now repeat 
the experiment, but instead of starting out at the 4 corners point, start the 
drag at an arbitrary point close to the next grid point above 4 corners, and 
again zoom to just include NM.   Look for your grid point and compare its 
location compared to where it was before.  The entire grid field is offset some 
amount.   This was disconcerning to us in that we were trying to pin down the 
location of a small meso-scale circulation, and the low was located in different
locations depending on how you zoomed.

Is this fixable in the next iteration of GEMPAK?

Thanks for looking into it.


John Hobbie
National Scientific Balloon Facility