20040812: Composite Radar Problems? (cont.)

>From: Tom McDermott <address@hidden>
>Organization: SUNY Brockport
>Keywords: 200408122329.i7CNTOaW008533 IDD FNEXRAD

Hi Tom,

re: chanes to FNEXRAD composite images created from GRIB messages

>I probably would have been unaware of it as well for a while were it not
>for the fact that I installed the latest version of gempak yesterday.  I
>emailed our met professors to let me know if anything was missing, not
>working, etc., and one of them notified of the problem with the composite
>radars.  So I'm relieved to find out that apparently it's not something I
>did that caused it.

My investigation revealed two different things that were causing
problems:

- the C module used to convert the GRIB message navigation to McIDAS
  format had an operator precedence logic error:

  code (btab.c) was:

  if ( !mode&0x80 ) {

  it should have been (and is now):

  if ( !(mode&0x80) ) {
  
  This code snippit is in the section where the scanning mode of the
  data in the GRIB message is used to determine the longitudnal
  increment between grid points.

- the version of the source for the McIDAS application that converts
  GRIB messages into images in AREA file format (grib2img.pgm) was a
  newer one than the one being used before my code modification, and
  this newer version did not include support for command line keywords
  needed to set header words that GEMPAK uses to determine which
  enhancement, etc  to use.  As Jim Koermer pointed out, McIDAS was not
  having problems with the images being created by the new routine.

>(I had pretty much verified that the new software was
>not at fault since the old software is giving me the same errors.)

The problem was a "versionitis"-related one.  I have upgraded the
executable being used to create FNEXRAD composites from GRIB messages.

Please let me know if you can now display the FNEXRAD composites, or
if there is still something missing for GEMPAK/GARP.

>Thanks for looking into this.

No worries.  It was my mod that caused the problems :-(

Cheers,

Tom
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