20020318: Stage 4 precip analyses

>From: "Arthur A. Person" <address@hidden>
>Organization: Penn State
>Keywords: 200203181441.g2IEf5a04222 IDD NEXRAD precipitation CONDUIT

Art,

>Was wondering if the Stage 4 Nexrad precipitation analyses from NCEP are
>sent on any of the IDD feeds.

Since neither Chiz nor I was familiar with these analyses, I had to do
a Google (tm) search to find out information.  A nice web page for the
precip analyses is:

http://www.emc.ncep.noaa.gov/mmb/stage2.old/

and an FAQ for the Stage IV stuff is:

http://www.emc.ncep.noaa.gov/mmb/research/stage4.FAQ.html

After reviewing these, we are of the opinion that the analyses are not
in the IDD.

>If not, any chance it could be added to NMC2 or somewhere?

Adding the grib messages to the CONDUIT feed would be problematic in
general, and would probably be best to not address at the moment as we
are working as hard as we can to get a stable and reliable CONDUIT feed
setup.

As for adding the 4 km grib messages to a feed other than CONDUIT (NMC2),
this would be possible, but current implementations of both GEMPAK and
McIDAS would not be able to handle them, so their usefulness would be
limited to those that would be willing to modify their distributions.

Information on the grib messages that are available by FTP from:

ftp://ftp.ncep.noaa.gov/pub/gcp/precip/stage2.old/

can be found in the FAQ listed above:

  WHAT IS THE GRID INFORMATION?
  
  The format of the files is GRIB. The files are compressed using the
  UNIX "compress" command and "uncompress" must be used before
  decoding.

  For the 4km grid:

       It is a 1160x880 polar stereographic grid.  Point (1,1) is at
       22.7736N 120.376W.  Point (1,880) is at 52.613N 136.394W.  Point
       (1160,1) is at 19.810N 80.802W.  Point (1160,880) is at 45.619N
       60.079W.  The y-axis is parallel to 105W.  The resolution is
       4.7625km at 60N.  The pole point is (I,J) = (441,1601)

  For the 15km grid:

       The 15km grid is simply a 3x3 averaged remapping of the 4km
       grid.  It is a 386x293 polar stereographic grid.  Point (1,1) is
       at 22.813N 120.351W.  Point (1,293) is at 52.564N 136.264W.
       Point (386,1) is at 19.876N 80.877W.  Point (386,293) is at
       45.646N 60.277W.  The y-axis is parallel to 105W.  The
       resolution is 14.2875km at 60N.  The pole point is (I,J) =
       (147.323,534)

You can see from the size of the 4 km grid that it is large:  1160x880
= 1020800 grid points.  The 15 km product is more easily used as it is
smaller: 386x293 = 113098 grid points.

All of this being said, we have not decided to never send these products.
Rather, we think that right now is not the appropriate time.

Tom Yoksas