GRIB2 Inventory¶

The wgrib2 utility provides capabilities for inspecting the contents of GRIB2 files without extracting the actual data. This is essential for understanding what variables, levels, and forecast times are contained in a GRIB2 file before processing. These are commonly called an "index" or "inventory" of the GRIB2 file.

Default Inventory¶

The simplest way to list a GRIB2 contents is to run wgrib2 with just the filename:

wgrib2 filename.grb2

which would output something like the following:

1:0:d=2024120800:TMP:2 m above ground:anl:
2:12345:d=2024120800:RH:2 m above ground:anl:
3:45678:d=2024120800:UGRD:10 m above ground:anl:

These :-separated values the following for each record in the GRIB2 file:

• Record number: Sequential message number in the file
• Byte offset: Starting position of each message
• Date: Reference time of the data in YYYYMMDDHH format
• Variable: Parameter name
• Level: Vertical level information
• Forecast time: Valid time or forecast hour

You will find that the following are equivalent:

wgrib2 filename.grib2
wgrib2 -s filename.grib2
wgrib2 -t -var -lev -ftime -misc filename.grib2

Inventory of a real HRRR file¶

Let's get and inspect an index file from the High-Resolution Rapid Refresh (HRRR) model:

wget https://noaa-hrrr-bdp-pds.s3.amazonaws.com/hrrr.20250102/conus/hrrr.t00z.wrfsfcf00.grib2

Since there are many records, lets just list the first five:

$ wgrib2 ./hrrr.t00z.wrfsfcf00.grib2 | head -n 5
1:0:d=2025010200:REFC:entire atmosphere:anl:
2:381614:d=2025010200:RETOP:cloud top:anl:
3:564153:d=2025010200:var discipline=0 center=7 local_table=1 parmcat=16 parm=201:entire atmosphere:anl:
4:1089819:d=2025010200:VIL:entire atmosphere:anl:
5:1476545:d=2025010200:VIS:surface:anl:

Create an index file¶

If you are producing or distributing GRIB2 files, it is best practice to also provide a simple inventory using the same filename with the .idx suffix.

wgrib2 -s filename.grib2 > filename.grib2.idx

Verbose Inventory (-V)¶

For detailed metadata about each record, use -V:

wgrib2 -V filename.grb2

Output includes:

• Grid definition
• Statistical processing information
• Ensemble member details
• Additional metadata fields

For our HRRR file:

$ wgrib2 -V ./hrrr.t00z.wrfsfcf00.grib2 | head -n 9
1:0:vt=2025010200:entire atmosphere:anl:REFC Composite reflectivity [dB]:
    ndata=1905141:undef=0:mean=-7.47602:min=-10:max=53.5
    grid_template=30:winds(grid):
        Lambert Conformal: (1799 x 1059) input WE:SN output WE:SN res 8
        Lat1 21.138123 Lon1 237.280472 LoV 262.500000
        LatD 38.500000 Latin1 38.500000 Latin2 38.500000
        LatSP 0.000000 LonSP 0.000000
        North Pole (1799 x 1059) Dx 3000.000000 m Dy 3000.000000 m

Match Specific Variables (-match)¶

Use the -match option to filter the inventory for only specific variables.

$ wgrib2 hrrr.t00z.wrfsfcf00.grib2 -match "TMP"
15:8303112:d=2025010200:TMP:500 mb:anl:
20:11626595:d=2025010200:TMP:700 mb:anl:
26:15543517:d=2025010200:TMP:850 mb:anl:
30:18468349:d=2025010200:TMP:925 mb:anl:
34:21454096:d=2025010200:TMP:1000 mb:anl:
64:32817321:d=2025010200:TMP:surface:anl:
71:36954241:d=2025010200:TMP:2 m above ground:anl:

$ wgrib2 hrrr.t00z.wrfsfcf00.grib2 -match ":(UGRD|VGRD|TMP):(700|500) mb:"
15:8303112:d=2025010200:TMP:500 mb:anl:
17:9723023:d=2025010200:UGRD:500 mb:anl:
18:10316390:d=2025010200:VGRD:500 mb:anl:
20:11626595:d=2025010200:TMP:700 mb:anl:
23:13614254:d=2025010200:UGRD:700 mb:anl:
24:14213777:d=2025010200:VGRD:700 mb:anl:

Filter by Level (-lev)¶

Show only records at specific levels:

wgrib2 -lev "2 m" filename.grb2
wgrib2 -lev "850 mb" filename.grb2

Combination Filtering¶

Combine options for precise searching:

wgrib2 -s -match "TMP" -lev "2 m" filename.grb2

Advanced Inventory Techniques¶

Count Records¶

Count the total number of records in a file:

wgrib2 filename.grb2 | wc -l

Search and Extract Information¶

Use grep to find specific information:

# Find all 500mb records
wgrib2 -s filename.grb2 | grep "500 mb"

# Find all temperature variables
wgrib2 -s filename.grb2 | grep ":TMP:"

# Find specific forecast hours
wgrib2 -s filename.grb2 | grep "3 hour fcst"

Custom Output Format (-v)¶

Create custom inventory formats:

wgrib2 -s -var -lev -ftime filename.grb2

This shows only variable name, level, and forecast time for each record.

Practical Use Cases¶

Case 1: Quick File Overview¶

Before processing a new GRIB2 file, get a quick overview:

wgrib2 -s filename.grb2 | head -20

Shows the first 20 records to understand file structure.

Case 2: Find Specific Data¶

Locate a specific variable at a specific level:

wgrib2 -s filename.grb2 | grep "TMP" | grep "850 mb"

Case 3: List All Variables¶

Get a unique list of all variables in the file:

wgrib2 -s filename.grb2 | cut -d: -f4 | sort -u

Case 4: List All Levels¶

Identify all vertical levels present:

wgrib2 -s filename.grb2 | cut -d: -f5 | sort -u

Case 5: Check Forecast Times¶

See all forecast times available:

wgrib2 -s filename.grb2 | cut -d: -f6 | sort -u

Output Format Reference¶

Standard Format Fields¶

The -s option produces colon-separated fields:

record:byte_offset:reference_date:variable:level:forecast_info:

Performance Tips¶

!!! note "Performance Considerations" - Inventory operations are fast since they only read GRIB2 headers, not data - Use -match and -lev to reduce output for large files - Pipe output to less for easier navigation: wgrib2 -s file.grb2 | less

Common Pitfalls¶

!!! warning "Common Issues" - Case sensitivity: Variable names and match patterns are case-sensitive - Level formats: Level descriptions vary (e.g., "850 mb" vs "850 MB") - Regex patterns: Use proper regex syntax with -match option

Additional Resources¶

For more advanced wgrib2 usage:

wgrib2 -help        # Display all available options
wgrib2 -help long   # Detailed help for all options

Summary¶

Quick reference for the most useful inventory commands: