Monthly average difference between ETA and RUC model forecasts

Notes:
>   The ETA model grid is used for all comparisons:  the monthly average value at each ETA grid point (12km resolution) has subtracted from it the monthly average value at the nearest RUC model grid point (20km resolution).
>   Due to differences in grid resolution between the models, the calculated parameter differences have much small-scale noise which should be ignored.  This is particularly noticeable near land-water boundaries, since those interface locations differ between models.  Due to the large differences that can occur in such cases, cut-off minima/maxima have been applied to some plots.
>  "Missing data" can occur near the outer boundaries due to locations not being covered by one of the two model region.  Such "missing data" is here plotted as a "zero" value. 
>   The forecast period used is the "latest" available on any day, which for the RUC model is usually 6 hours and for the ETA model usually 6 and 9 hours for 18Z and 21Z validation times respectively.
>   If there is no available plot for a selected region/parameter/month, a "NO DATA" message should then appear after clicking the "INSERT MAP" button.  However, for some browsers the javascript then gets discombobulated and will not correctly load subsequent plot requests - if this occurs, reloading the viewer is necessary to view further plots.  (So if you are unable to load a plot which you think should exist, try reloading the viewer!)
>   New difference plots should be available on the second of each month.

TO CREATE A BLIPMAP IMAGE SEQUENCE:
(1) Select a region, month, and parameter
(2) Single click the "INSERT MAP" button
(3) Repeat for additional region/month/parameter(s)
(4) Single click "FRAME" buttons to move through images
Notes:
    "INSERT MAP" button inserts selected map following the current image
    "List LOAD" button loads lastest maps in saved image list  (use to load favorite images)
    "List SAVE" button creates new saved image list from present image list  (uses cookie to save favorite image list)
    "New Cache" button enables replacement of existing images in cache
    "DELETE Bkd" button deletes the current image and displays the preceeding image
    "DELETE Fwd" button deletes the current image and displays the following image