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[THREDDS #DBI-852054]: thredds nbm dataset

Greetings!

See inline below:

> At various times, two snow accumulation variables appear in the dataset.
> https://thredds.ucar.edu/thredds/ncss/grib/NCEP/NBM/CONUS/Best/dataset.html
> 
> 1. Total_snowfall_surface_1_Hour_Accumulation (with Time coordinate
> time7)
> 2. Total_snowfall_surface_Mixed_intervals_Accumulation (with Time
> coordinate time6)
>
> Neither of these variables is documented in the NCEP nbm documentation.
> 1. Exactly what data is represented in these variables?

I'm not sure why there was a separate hourly accumulation, but currently on the 
mixed interval version is available. This is the standard snow accumulation 
that is documented here:

  https://vlab.noaa.gov/web/mdl/nbm-wx-elements

> 2. How many hours does each variable cover in a dataset?
> 3. Which hourly runs produce which variables?

Here is NCEP's documentation for how many hours each variable extends to for 
each forecast run--for what's distributed on NOAAPORT, which is what provides 
the data we host on THREDDS:

  
https://www.weather.gov/media/mdl/nbm/docs_v40/NBM_v40_Elements_on_SBN_by_Cycle_ALL.pdf

> 4. What does time7 and time6 mean?

time6 means it was the 6th unique time coordinate identified by netcdf-java as 
it scanned through the grib file; time7 is the 7th. These are just trying to 
come up with unique dimension names given the diverse set of different times 
(reference time and valid time) in the GRIB collection.

> 5. To always get the latest model run, what time range should I request?

If you use the "Best" dataset, as linked, you'll get a collection of the times 
closest to the range requested, with the smallest forecast offset (e.g. 12 hour 
vs. 96 hour)

> 6. What is the "stride"?

How big a step to take through the data. If your requested time range of 0-12 
with hourly data, a request with a stride of 3 will give (0, 3, 6, 9, 12).

> 7. How would I select a previous model run?

Either manually find the appropriate run time that contains the data you need 
from the full list here:

  https://thredds.ucar.edu/thredds/catalog/grib/NCEP/NBM/CONUS/catalog.html

Or use the Full collection, and subset using the reftime for the forecast you 
want:

  https://thredds.ucar.edu/thredds/catalog/grib/NCEP/NBM/CONUS/catalog.html

Hope this helps!

Ryan

Ticket Details
===================
Ticket ID: DBI-852054
Department: Support THREDDS
Priority: Normal
Status: Closed
===================
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