thredds field download problems

[Kenneth schaudt]

Hope someone may have a suggestion.  Downloads of Hycom fields have been
failing the past few days.

Attempts to download information a field in the gulf of mexico are
failing as shown below.

As I understand, this usually occurs when the files on Hycom are being
updated.  In this case, download requests have been failing as shown
below for the past 2 days.



Wed Jul  9 09:36:02 CDT 2025
+ ncks -D0 -d time,2025-07-09T00:00:00Z,2025-07-15T23:00:00Z -v
water_temp -d lat,20.,35. -d lon,260.,280. -d depth,0.
http://tds.hycom.org/thredds/dodsC/FMRC_ESPC-D-V02_ts3z/FMRC_ESPC-D-V02_ts3z_best.ncd
-O ../data/FMRC_ESPC-D-V02_ts3z_best_0m.nc4
ncks: INFO DAP-access to
http://tds.hycom.org/thredds/dodsC/FMRC_ESPC-D-V02_ts3z/FMRC_ESPC-D-V02_ts3z_best.ncd
failed with error code -73. Translation into English with
nc_strerror(-73) is "NetCDF: Malformed or inaccessible DAP2 DATADDS or
DAP4 DAP response"
ncks: WARNING not searching for
http://tds.hycom.org/thredds/dodsC/FMRC_ESPC-D-V02_ts3z/FMRC_ESPC-D-V02_ts3z_best.ncd
on remote filesystem, using local file
hredds/dodsC/FMRC_ESPC-D-V02_ts3z/FMRC_ESPC-D-V02_ts3z_best.ncd instead
ERROR: nco__open() unable to open file
"thredds/dodsC/FMRC_ESPC-D-V02_ts3z/FMRC_ESPC-D-V02_ts3z_best.ncd"
ERROR NC_ENOTNC Not a netCDF file
HINT: NC_ENOTNC errors can occur for many reasons. If your use-case
matches one of the five listed below, take the corrective action indicated:
1. The netCDF file is truly corrupt, e.g., truncated. To verify whether
the file is corrupt, try, e.g., printing its metadata with 'ncks -m
in.nc'. This test will likely fail on a corrupt file
2. An NCO operator linked only to the classic netCDF3 library attempts
to read netCDF4 (or HDF5) files. However, this executable seems to have
been built with the capability to manipulate netCDF4 files, so it is
unlikely that this command failed only because the input datasets are
netCDF4 format. Something else is going wrong.
3. NCO attempts to read other filetypes (HDF4, HDF-EOS2, PnetCDF/CDF5)
for which support must be (but was not) enabled at netCDF build-time.
NCO can access HDF4 files if NCO is first re-linked to a version of
netCDF configured with the --enable-hdf4 option. This is a non-standard
netCDF build option described here:
http://www.unidata.ucar.edu/software/netcdf/docs/build_hdf4.html. NCO
can access PnetCDF/CDF5 files if NCO is first re-linked to netCDF
version 4.4.0 or later.
4. NCO attempts to utilize diskless (i.e., RAM) files.  In this case
remove the diskless switches (e.g., --ram or --diskless) and then
re-issue the command.
5. Access to a DAP URL fails, and the backup method of downloading the
URL using wget obtains a data aggregation file (e.g., a .ncml file)
instead of an actual netCDF file. In this case the problem is with the
DAP server or URL.
nco_err_exit(): ERROR Short NCO-generated message (usually name of
function that triggered error): nco__open()
nco_err_exit(): ERROR Error code is -51. Translation into English with
nc_strerror(-51) is "NetCDF: Unknown file format"
nco_err_exit(): ERROR NCO will now exit with system call exit(EXIT_FAILURE)