Gridded LAMP GRIB2 Encoding Details


The GFS-based Gridded LAMP gridded guidance is provided on the 2.5km Lambert Conformal grid covering the same expanse as the National Digital Forecast Database (NDFD) CONUS grid in GRIB2 format. Beginning September 28, 2010, GRIB2 files will be available in the Experimental National Digital Guidance Database (NDGD). For current status of the files on the server, and descriptions of the file locations and names please refer to https://www.weather.gov/mdl/lamp_NWS_tgftp_server. The files in NDGD contain multiple grids in each file, grouped by element.

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

Section 0 - Indicator Section

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

Section 1 - Identification Section

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 LAMP Thunderstorm products.
 

Section 3 - Grid Definition Section

The Gridded LAMP guidance is presented on the 2.5-km NDFD grid. The following are the grid specifications used to pack the guidance into GRIB2.
2.5km CONUS Grid -- Image available here
Octet No. Value Explanation
1-4 81 Length of section in octets
5 3 Number of Section
6 0 Grid definition template defined in Octet 13-14
7-10 2953665 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 2145 NX
35-38 1377 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 2539703 Dx- grid length in x direction
60-63 2539703 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

Section 4 - Product Definition Section

The Gridded LAMP products are packed using Product Definition Template (PDT) 4.0. The following tables list the settings for each element for observations and forecasts.
Observation Guidance Valid at a Point in Time - PDT 4.0
Octet No. 2-M Temp Obs (K) 2-M Temp Obs Err Est. (K) 2-M Dew Point Obs (K) 2-M Dew Point Obs Err Est. (K) Ceiling Hgt Obs (m) Visibility Obs (m) Wind Speed Obs (m/s) Wind Direction Obs (degrees) Opaque Sky Cover Obs (%) Wind Gust Obs (m/s)
1-4 Length of section in octets
5 4
6-7 0
8-9 0
10 0 0 0 0 6 19 2 2 6 2
11 0 0 6 6 13 0 1 0 1 22
12 0 7 0 7 0 0 0 0 0 0
13 missing
14 108
15-16 missing
17 missing
18 1
19-22 hours from reference time to valid time (i.e. projection)
23 103 103 103 103 215 1 103 103 1 103
24 0
25-28 2 2 2 2 0 0 10 10 0 10
29 missing
30 0
31-34 0
Forecast Guidance Valid at a Point in Time - PDT 4.0
Octet No. 2-M Temp Fcst (K) 2-M Dew Point Fcst (K) Ceiling Hgt Fcst (m) Visibility Fcst (m) Wind Speed Fcst (m/s) Wind Direction Fcst (degrees) Opaque Sky Cover Fcst (%) Wind Gust Fcst (m/s) Ceiling Height Probabilities Fcst (%) Visibility Probabilities Fcst (%)
1-4 Length of section in octets
5 4
6-7 0
8-9 0 5 5
10 0 0 6 19 2 2 6 2 6 19
11 0 6 13 0 1 0 1 22 13 0
12 2 5 5
13 missing
14 108
15-16 missing
17 missing
18 1
19-22 hours from reference time to valid time (i.e. projection)
23 103 103 215 1 103 103 1 103 215 1
24 0
25-28 2 2 0 0 10 10 0 10 0 0
29 missing
30 0
31-34 0
35 N/A 2 for < 500ft, 3 for < 1000ft, and 5 for <= 3000ft 2 for < 1mi, 4 for < 3mi, and 5 for <= 5mi
36 N/A 7 6
37 N/A 0 0
38 N/A 2 2
39-42 N/A 15240 for < 500ft, 30480 for < 1000ft, and 91450 for <= 3000ft 160934 for < 1mi, 482803 for < 3mi, and 804673 for <= 5mi
43 N/A missing missing
44-47 N/A missing missing

Section 5 - Data Representation Section

We use Data Representation Template 5.3: Gridpoint data - complex packing and spatial differencing.

For decimal scaling, we use the following decimal scaling factors:
Temperatures Ceiling Height Visibility Wind Speed Wind Direction Opaque Sky Cover Wind Gust Ceiling Height Probabilities Visibility Probabilities
1 0 0 1 -1 0 1 0 0
Binary scaling is used on selected Gridded LAMP 2.5 km grids. Learn more about binary scaling. The following binary scaling factors are used:
Temperatures Ceiling Height Visibility Wind Speed Wind Direction Opaque Sky Cover Wind Gust Ceiling Height Probabilities Visibility Probabilities
2 3 7 2 0 0 2 0 0

Please see the LAMP Documentation Page for further details.