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LAMP GRIB2 Encoding Details

The GFS-based LAMP thunderstorm guidance is provided on the 5km NDFD grid in GRIB2 format. The products are disseminated via two mechanisms. GRIB2 files are available on the NWS FTP server. Please refer to https://www.weather.gov/mdl/lamp_NWS_tgftp_server for the current status of the files on the server, as well as descriptions of the file locations and names available. The files on the ftp server contain multiple grids in each file, grouped by element. The LAMP thunderstorm products are also available via the NWS Satellite Broadcast Network (SBN) and NOAAPORT. Please refer to Section C (pdf) for more information on 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.

Note: This page will be updated in January 2014 for LAMP convection and upgraded lightning GRIB2 details.


Section 0 - Indicator Section

For all LAMP Thunderstorm 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 LAMP Thunderstorm guidance is presented on the 5-km NDFD grid. The following are the grid specifications used to pack the guidance into GRIB2.

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 6 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

Section 4 - Product Definition Section

The LAMP Thunderstorm products are packed using Product Definition Template (PDT) 4.8. The following tables list the settings for each element.

Guidance Valid Over a Period of Time
Octet No. 2-hr Thunderstorm Probability Forecast (%) 2-hr Categorical Thunderstorm Forecast (Yes/No)
1-4 Length of section in octets Length of section in octets
5 4 4
6-7 0 0
8-9 8 8
10 19 19
11 2 203
12 5 2
13 missing missing
14 108 108
15-16 missing missing
17 missing missing
18 1 1
19-22 hours from reference time to beginning of forecast period
23 1 1
24 0 0
25-28 0 0
29 missing missing
30 0 0
31-34 0 0
35-36 Year of end of forecast period Year of end of forecast period
37 Month of end of forecast period Month of end of forecast period
38 Day of end of forecast period Day of end of forecast period
39 Hour of end of forecast period Hour of end of forecast period
40 Minute of end of forecast period Minute of end of forecast period
41 Second of end of forecast period Second of end of forecast period
42 1 1
43-46 0 0
47 missing missing
48 missing missing
49 1 1
50-53

2

2

54 missing missing
55-58 missing missing

Section 5 - Data Representation Section

We use Data Representation Template 5.3: Gridpoint data - complex packing and spatial differencing. For scaling, we use the following decimal scaling factors:

2-hr Thunderstorm Probability Forecast (%) 2-hr Categorical Thunderstorm Forecast (Yes/No)
0 0