Gridded MOS GRIB2 Encoding Details

The GFS-based Gridded MOS guidance is provided on the 5km NDFD grid in GRIB2 format. The products are disseminated via two mechanisms. GRIB2 files are currently available on the NWS FTP server. Descriptions of the file locations and names are available. The files on the ftp server contain multiple grids in each file, grouped by element. The gridded MOS products are also officially disseminated via the NWS Satellite Broadcast Network (SBN) and NOAAPORT. The guidance is sent with each grid as a separate product with its own unique WMO header. Click here for more details about the WMO headers.

This webpage seeks to provide users with some of the settings we are using to encode our products in GRIB2. Users should consult the WMO's GRIB2 handbook for the complete details on GRIB2 encoding.

Section 0 - Indicator Section

For all Gridded MOS GRIB2 prodcuts we set octet 7, Discipline, to 0 for Meteorological. We use GRIB edition 2 in octet 8.

Section 1 - Identification Section

Select Octet No.	Value	Explanation
6-7	7	Originating Center - NCEP
8-9	14	Originating Sub-center - MDL
10	1	initial operational version number
11	0	Version of local tables
12	1	Significance of date in Octets 13-19
13-19	Year, Month, Day, Hr, Min, Sec	Date of model run on which guidance is based
20	0	Operational products
21	1	Forecast products

Section 2 - Local Use Section

This section is not used in the Gridded MOS products

Section 3 - Grid Definition Section

The Gridded MOS guidance is presented on the 5-km NDFD grid for the CONUS and a 3km grid for Alaska. The following are the grid specifications used to pack the guidance into GRIB2.

5km CONUS grid -- Image available here
Octet No.	Value	Explanation
1-4	TBD	Length of section in octets
5	3	Number of Section
6	0	Grid definition template defined in Octet 13-14
7-10	739297	Number of data points
11	0	Number of non-rectangular points
12	0	No appended list of points
13-14	30	Lambert Conformal GDT
15	1	Spherical earth, radius in Octet 16-20
16	0	Scale factor of radius of spherical earth
17-20	6371200	Scaled value of radius of spherical earth
21	missing
22-25	missing
26	missing
27-30	missing
31-34	1073	NX
35-38	689	NY
39-42	20192000	Latitude of first grid point
43-46	238446000	Longitude of first grid point
47	48	Resolution and component flags
48-51	25000000	Latitude where Dx and Dy are specified
52-55	265000000	Longitude of parallel meridian
56-59	5079406	Dx - grid length in x direction
60-63	5079406	Dy - grid length in y direction
64	0	Projection centre flag
65	80	data scanned boustrophedonically
66-69	25000000	Latin 1
70-73	25000000	Latin 2
74-77	-90000000	Latitude of southern pole
78-81	0	Longitude of southern pole

3km Alaska grid -- Image available here
Octet No.	Value	Explanation
1-4	TBD	Length of section in octets
5	3	Number of Section
6	0	Grid definition template defined in Octet 13-14
7-10	1822145	Number of data points
11	0	Number of non-rectangular points
12	0	No appended list of points
13-14	20	Polar Stereographic GDT
15	1	Spherical earth, radius in Octet 16-20
16	0	Scale factor of radius of spherical earth
17-20	6371200	Scaled value of radius of spherical earth
21	missing
22-25	missing
26	missing
27-30	missing
31-34	1649	NX
35-38	1105	NY
39-42	40530100	Latitude of first grid point
43-46	181429000	Longitude of first grid point
47	0	Resolution and component flags
48-51	60000000	Latitude where Dx and Dy are specified
52-55	210000000	Orientation of the grid
56-59	2976560	Dx - grid length in x direction
60-63	2976560	Dy - grid length in y direction
64	0	Projection centre flag
65	80	data scanned boustrophedonically

Section 4 - Product Definition Section

The Gridded MOS products are packed using either Product Definition Template (PDT) 4.0, 4.8, or 4.9. The following tables list the settings for each element.

Guidance Valid at a Point in Time - PDT 4.0
Octet No.	2-M Temperature (K)	2-M Dewpoint (K)	Relative Humidity (%)	Wind Speed (m/s)	Wind Direction (degrees)	Wind Gusts (m/s)	Opaque Sky Cover (%)
1-4	Length of section in octets
5	4
6-7	0
8-9	0
10	0	0	1	2	2	2	6
11	0	6	1	1	0	22	1
12	2
13	missing
14	96
15-16	missing
17	missing
18	1
19-22	hours from reference time to valid time (i.e. projection)
23	103	103	103	103	103	103	1
24	0
25-28	2	2	2	10	10	10	0
29	missing
30	0
31-34	0

Guidance Valid Over a Period of Time - PDT 4.8 (see below for POPs)
Octet No.	Maximum Temperature (K)	Minimum Temperature (K)	Snowfall Amt (m)	3-hr tstm (%)	6-hr tstm (%)	12-hr tstm (%)	*6-hr Precip Amount (kg/m2)**	*12-hr Precip Amount (kg/m2)**
1-4	Length of section in octets
5	4
6-7	0
8-9	8
10	0	0	1	19	19	19	1	1
11	4	5	29	2	2	2	8	8
12	2	2	2	5	5	5	2	2
13	missing
14	96
15-16	missing
17	missing
18	1
19-22	hours from reference time to beginning of forecast period
23	103	103	1	1	1	1	1	1
24	0
25-28	2	2	0	0	0	0	0	0
29	missing
30	0
31-34	0
35-36	Year of end of forecast period
37	Month of end of forecast period
38	Day of end of forecast period
39	Hour of end of forecast period
40	Minute of end of forecast period
41	Second of end of forecast period
42	0		1
43-46	0
47	missing		1	missing			1
48	missing
49	missing		1
50-53	missing		24	3	6	12	6	12
54	missing
55-58	missing

Guidance Valid Over a Period of Time - PDT 4.9 -- POPs
Octet No.	6-hr POP (%)	12-hr POP (%)
1-4	Length of section in octets
5	4
6-7	0
8-9	9
10	1
11	8
12	2
13	missing
14	96
15-16	missing
17	missing
18	1
19-22	hours from reference time to beginning of forecast period
23	1
24	0
25-28	0
29	missing
30	0
31-34	0
35	missing
36	missing
37	1
38	missing
39-42	missing
43	3
44-47	254
48-49	Year of end of forecast period
50	Month of end of forecast period
51	Day of end of forecast period
52	Hour of end of forecast period
53	Minute of end of forecast period
54	Second of end of forecast period
55	1
56-59	0
60	1
61	missing
62	1
63-66	6	12
67	1
68	0

Section 5 - Data Representation Section

We use Data Representation Template 5.3: Gridpoint data - complex packing and spatial differencing. All fields are packed as floating point values except for wind direction which is packed as an integer.

For scaling, we use the following decimal scaling factors:

Temperatures	Wind Speed/Gusts	Wind Direction	Percentages (POP, RH and Opaque Sky)	Precipitation Amt	Snowfall Amt
1	1	0	0	3	5

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National Weather Service Office Of Science and Technology Meteorological Development Laboratory Statistical Modeling Branch 1325 East West Highway Silver Spring, MD 20910 Page last modified: 22 Mar 2007 Page Author: MOS Web Team	Disclaimer Credits Glossary	Privacy Policy