National Water Model
Overview
The National Water Model (NWM) is a hydrologic modelling framework that simulates observed and forecast streamflow over the entire continental United States (CONUS), Hawaii, and Puerto Rico. The NWM simulates the water cycle with mathematical representations of the different processes and how they fit together. This complex representation of physical processes such as snowmelt and infiltration and movement of water through the soil layers varies significantly with changing elevations, soils, vegetation types and a host of other variables. Additionally, extreme variability in precipitation over short distances and times can cause the response on rivers and streams to change very quickly. Overall, the process is so complex that to simulate it with a mathematical model means that it needs a very high powered computer or supercomputer in order to run in the time frame needed to support decision makers when flooding is threatened.
Storage Resources
The files are available from the Azure Blob Storage Container at https://noaanwm.blob.core.windows.net/nwm. This storage container is in Azure’s East US region. Users wishing to perform large-scale processing on the data should also locate their compute in Azure’s East US region. All data files are NetCDF4 file format.
The files vary along several facets. Each filename within the container will start with
nwm.YYYYMMDD/
where YYYY is the 4-digest year, MM is the two-diget month, and DD is the two diget day. Within that day’s directory are a set of directories combining various analyses, forecast configurations, and regions.
Data coverage areas and output variations
Data products may be available for Hawaii and Puerto Rico. This is indicated below for each product.
The data for Hawaii follows the same file name pattern, but have a prefix of nwm.{YYYYMMDD}/{product}_hawaii/ and files are suffixed with hawaii.nc instead of conus.nc. For example, the NWM Analysis and Assimilation product for Hawaii has the prefix nwm.{YYYYMMDD}/analysis_assim_hawaii/nwm.t{CC}z.analysis_assim.
The data for Puerto Rico follows the same file name pattern, but have a prefix of nwm.{YYYYMMDD}/{product}_puertorico/ and files are suffixed with puertorico.nc instead of conus.nc. For example, the NWM Analysis and Assimilation product for Puerto Rico has the prefix nwm.{YYYYMMDD}/analysis_assim_puertorico/nwm.t{CC}z.analysis_assim.
In addition, several channel outputs have separate open loop companion configuration, labeled “no_da”, which is the same as the respective normal configuration but does not have assimilation data applied. These products are described indicated below as separate entries.
There is also “Extended” versions of the Analysis Assimilation products, including “no_da” products. These filenames follow the same patterns as the non-extended product, but with _extend suffixed to the product name. For example: nwm.20210906/analysis_assim_extend/nwm.t16z.analysis_assim_extend.channel_rt.tm00.conus.nc
NWM Analysis and Assimilation
Analysis and Assimilation data for the CONUS, Hawaii and Puerto Rico. The files for CONUS begins with the prefix nwm.{YYYYMMDD}/analysis_assim/nwm.t{CC}z.analysis_assim where
YYYYis the 4-digest yearMMis the two-digit monthDDis the two digit dayCCis the model cycle runtime (i.e. 00, 06, 12, 18)PPis the model lookback period (i.e. 00, 01, 02)FFFis the forecast hour (i.e. 000, 006, 012, 018, etc)MEMis the forecast ensemble member (1-4 for long-range, 1-7 for medium-range)
| Description | Filename Pattern | Example |
|---|---|---|
| Point-type Channel Routing | {prefix}.analysis_assim.channel_rt.tm{PP}.conus.nc |
https://noaanwm.blob.core.windows.net/nwm/nwm.20230123/analysis_assim/nwm.t00z.analysis_assim.channel_rt.tm00.conus.nc |
| 1km gridded Land Output | {prefix}.land.tm{PP}.conus.nc |
https://noaanwm.blob.core.windows.net/nwm/nwm.20230123/analysis_assim/nwm.t00z.analysis_assim.land.tm00.conus.nc |
| Point-type Reservoir Output | {prefix}.reservoir.tm{PP}.conus.nc |
https://noaanwm.blob.core.windows.net/nwm/nwm.20230123/analysis_assim/nwm.t00z.analysis_assim.reservoir.tm00.conus.nc |
| 250m gridded Terrain Routing | {prefix}.terrain_rt.tm{PP}.conus.nc |
https://noaanwm.blob.core.windows.net/nwm/nwm.20230123/analysis_assim/nwm.t00z.analysis_assim.terrain_rt.tm00.conus.nc |
Analysis and Assimilation data is available for the Continental United States, Hawaii and Puerto Rico.
Analysis and Assimilation Long data for the Continental United States. Each file begins with the prefix nwm.{YYYYMMDD}/analysis_assimi_long/nwm.t{CC}z.analysis_assim_long, using similar notation as above.
| Description | Filename Pattern | Example |
|---|---|---|
| Point-type Channel Routing | {prefix}.channel_rt.tm{PP}.conus.nc |
https://noaanwm.blob.core.windows.net/nwm/nwm.20230123/analysis_assim_long/nwm.t00z.analysis_assim_long.channel_rt.tm00.conus.nc |
| 1km gridded Land Output | {prefix}.land.tm{PP}.conus.nc |
https://noaanwm.blob.core.windows.net/nwm/nwm.20230123/analysis_assim_long/nwm.t00z.analysis_assim_long.land.tm00.conus.nc |
| Point-type Reservoir Output | {prefix}.reservoir.tm{PP}.conus.nc |
https://noaanwm.blob.core.windows.net/nwm/nwm.20230123/analysis_assim_long/nwm.t00z.analysis_assim_long.reservoir.tm00.conus.nc |
Analysis and Assimilation Long data is available only for the Continental United States.
Analysis and Assimilation Forcing data for the Continental United States. Each file begins with the prefix nwm.{YYYYMMDD}/forcing_analysis_assimi/nwm.t{CC}z.analysis_assim, using similar notation as above.
| Description | Filename Pattern | Example |
|---|---|---|
| 1km Gridded Forcing Data | {prefix}.forcing.tm{PP}.conus.nc |
https://noaanwm.blob.core.windows.net/nwm/nwm.20230123/forcing_analysis_assim/nwm.t00z.analysis_assim.forcing.tm00.conus.nc |
Likewise for Hawaii and Puerto Rico.
Analysis and Assimilation (No DA) data for the Continental United States, Hawaii, and Puerto Rico. Each file begins with the prefix nwm.{YYYYMMDD}/analysis_assimi_no_da/nwm.t{CC}z.analysis_assim_no_da, using similar notation as above.
| Description | Filename Pattern | Example |
|---|---|---|
| Point-type Channel Routing (No DA) | {prefix}.channel_rt.tm{PP}.conus.nc |
https://noaanwm.blob.core.windows.net/nwm/nwm.20230123/analysis_assim_no_da/nwm.t00z.analysis_assim_no_da.channel_rt.tm00.conus.nc |
Analysis and Assimilation (No DA) data is available for the Continental United States, Hawaii and Puerto Rico.
Analysis and Assimilation Long (No DA) data for the Continental United States. Each file begins with the prefix nwm.{YYYYMMDD}/analysis_assimi_long_no_da/nwm.t{CC}z.analysis_assim_long_no_da, using similar notation as above.
| Description | Filename Pattern | Example |
|---|---|---|
| Point-type Channel Routing (No DA) | {prefix}.channel_rt.tm{PP}.conus.nc |
https://noaanwm.blob.core.windows.net/nwm/nwm.20230123/analysis_assim_long_no_da/nwm.t00z.analysis_assim_long_no_da.channel_rt.tm00.conus.nc |
Analysis and Assimilation Long (No DA) data is available only for the Continental United States.
NWM Short Range
Short range forecast data for the Continental United States, Hawaii, and Puerto Rico. Each file begins with the prefix nwm.{YYYYMMDD}/short_range/nwm.t{CC}z.short_range, using similar notation as above.
| Description | Filename Pattern | Example |
|---|---|---|
| Point-type Channel Routing | {prefix}.channel_rt.f{FFF}.conus.nc |
https://noaanwm.blob.core.windows.net/nwm/nwm.20230123/short_range/nwm.t00z.short_range.channel_rt.f001.conus.nc |
| 1km gridded Land Output | {prefix}.land.f{FFF}.conus.nc |
https://noaanwm.blob.core.windows.net/nwm/nwm.20230123/short_range/nwm.t00z.short_range.land.f001.conus.nc |
| Point-type Reservoir Output | {prefix}.reservoir.f{FFF}.conus.nc |
https://noaanwm.blob.core.windows.net/nwm/nwm.20230123/short_range/nwm.t00z.short_range.reservoir.f001.conus.nc |
| 250m gridded Terrain Routing | {prefix}.terrain_rt.f{FFF}.conus.nc |
https://noaanwm.blob.core.windows.net/nwm/nwm.20230123/short_range/nwm.t00z.short_range.terrain_rt.f001.conus.nc |
Analysis and Assimilation (No DA) data is available for the Continental United States, Hawaii and Puerto Rico.
Short Range Forcing data for the Continental United States, Hawaii, and Puerto Rico. Each file begins with the prefix nwm.{YYYYMMDD}/forcing_short_range/nwm.t{CC}z.short_range, using similar notation as above.
| Description | Filename Pattern | Example |
|---|---|---|
| 1km Gridded Forcing Data | {prefix}.forcing.f{FFF}.conus.nc |
https://noaanwm.blob.core.windows.net/nwm/nwm.20230123/forcing_short_range/nwm.t00z.short_range.forcing.f001.conus.nc |
Likewise for Hawaii and Puerto Rico.
Note that Hawaii and Puerto Rico also include Short Range NO-DA data.
NWM Medium Range
Medium range forecast data for the Continental United States. Each file begins with the prefix nwm.{YYYYMMDD}/medium_range/nwm.t{CC}z.medium_range_mem{MEM}, using similar notation as above ({MEM} refers to the ensemble member).
| Description | Filename Pattern | Example |
|---|---|---|
| Point-type Channel Routing | {prefix}.channel_rt_{MEM}.f{FFF}.conus.nc |
https://noaanwm.blob.core.windows.net/nwm/nwm.20230123/medium_range_mem1/nwm.t00z.medium_range.channel_rt_1.f001.conus.nc |
| 1km gridded Land Output | {prefix}.land_{MEM}.f{FFF}.conus.nc |
https://noaanwm.blob.core.windows.net/nwm/nwm.20230123/medium_range_mem1/nwm.t00z.medium_range.land_1.f003.conus.nc |
| Point-type Reservoir Output | {prefix}.reservoir_{MEM}.f{FFF}.conus.nc |
https://noaanwm.blob.core.windows.net/nwm/nwm.20230123/medium_range_mem1/nwm.t00z.medium_range.reservoir_1.f001.conus.nc |
| 250m gridded Terrain Routing | {prefix}.terrain_rt_{MEM}.f{FFF}.conus.nc |
https://noaanwm.blob.core.windows.net/nwm/nwm.20230123/medium_range_mem1/nwm.t00z.medium_range.terrain_rt_1.f003.conus.nc |
Medium-range forecast data are only available for the Continental United States.
Medium Range Forcing data for the Continental United States. Each file begins with the prefix nwm.{YYYYMMDD}/forcing_medium_range/nwm.t{CC}z.medium_range, using similar notation as above.
| Description | Filename Pattern | Example |
|---|---|---|
| 1km Gridded Forcing Data | {prefix}.forcing.f{FFF}.conus.nc |
https://noaanwm.blob.core.windows.net/nwm/nwm.20230123/forcing_medium_range/nwm.t00z.medium_range.forcing.f001.conus.nc |
Medium-range forcing data are only available for the Continental United States.
NWM Long Range
Long-range forecasts are available for the Continental United States. Each file begins with the prefix nwm.{YYYYMMDD}/long_range/nwm.t{CC}z.long_range_mem{MEM}, using similar notation as above ({MEM} refers to the ensemble member).
| Description | Filename Pattern | Example |
|---|---|---|
| Point-type Channel Routing | {prefix}.channel_rt_{MEM}.f{FFF}.conus.nc |
https://noaanwm.blob.core.windows.net/nwm/nwm.20230123/long_range_mem1/nwm.t00z.long_range.channel_rt_1.f006.conus.nc |
| 1km gridded Land Output | {prefix}.land_{MEM}.f{FFF}.conus.nc |
https://noaanwm.blob.core.windows.net/nwm/nwm.20230123/long_range_mem1/nwm.t00z.long_range.land_1.f024.conus.nc |
| Point-type Reservoir Output | {prefix}.reservoir_{MEM}.f{FFF}.conus.nc |
https://noaanwm.blob.core.windows.net/nwm/nwm.20230123/long_range_mem1/nwm.t00z.long_range.reservoir_1.f001.conus.nc |
Long-range forecast data are only available for the Continental United States.
USGS Observations
USGS Timeslices 15-minute observation data for the Continental United States. Each file begins with the prefix nwm.{YYYYMMDD}/usgs_timeslices, using similar notation as above.
| Description | Filename Pattern | Example |
|---|---|---|
| 15-minute observation | {prefix}/{YYYY}-{MM}-{DD}_HH:mm:ss.15min.usgsTimeSlice.ncdf |
https://noaanwm.blob.core.windows.net/nwm/nwm.20230123/usgs_timeslices/2023-01-23_00%3A00%3A00.15min.usgsTimeSlice.ncdf |
where
HHis the two-digit hour of the daymmis the two-digit minute of the hourssis the two-digit second of the minute
USGS Timeslices data are only available for the Continental United States.
Example
This example shows loading a short-range forecast for the Continental United States and plotting the soil saturation.
>>> import adlfs
>>> import xarray as xr
>>> fs = adlfs.AzureBlobFileSystem("noaanwm")
>>> prefix = "nwm/nwm.20230123"
>>> ds = xr.open_dataset(fs.open(f"{prefix}/short_range/nwm.t00z.short_range.land.f001.conus.nc"))
>>> soil_saturation = ds["SOILSAT_TOP"].load()
>>> soil_saturation.coarsen(x=4, y=4, boundary="trim").mean().plot(figsize=(16, 10))
Which produces the figure
See the example notebook for more.