Accessing HYCOM Hindcasts using Siphon: OPENDAP is not available for this dataset

Question

I've got a working example of using Siphon to access the HYCOM forecast model run catalog (FMRC), and I really like this pattern! My problem is that I cannot access the hindcast catalog in the same way.

Here is what works, note the THREDDS catalog URL and how the HTML appears in a browser:

from siphon.catalog import TDSCatalog
thredds_url_fmrc = "https://tds.hycom.org/thredds/catalog/GLBy0.08/expt_93.0/FMRC/runs/catalog.xml"
cat_fmrc = TDSCatalog(thredds_url_fmrc)
ds_fmrc = cat_fmrc.datasets[0].remote_access()

Here is what does not work:

from siphon.catalog import TDSCatalog
thredds_url_hind = "https://tds.hycom.org/thredds/catalogs/GLBy0.08/expt_93.0.xml"
cat_hind = TDSCatalog(thredds_url_hind)
ds_hind = cat_hind.datasets[0].remote_access()

This returns ValueError: OPENDAP is not available for this dataset.

Note that both the FMRC and hindcasts are nested within this higher level catalog. The browser-rendered catalog pages for the FMRC look quite different that what is available for the hindcast data, but the hindcast data does indicate the catalog entry as I've used in the above example.

I feel like I'm just pointing Siphon at the wrong URL, or that the HYCOM THREDDS server has perhaps been disabled for higher level requests that are too big?

I've cross-posted this issue with less Siphon specificity on the HYCOM user's group.

Any help/input is appreciated!

Answer 1

This looks like a bug somewhere in Siphon. Unfortunately, I haven't been able to figure out a work-around, so right now you'll have to copy the correct OPeNDAP URL and pass that to Dataset from netCDF4-python or xarray.open_dataset manually. I've opened this issue to look at later.