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LAMP Convection and Lightning GRIB2 Encoding Details

The LAMP convection and lightning guidance is provided on the 2.5km NDFD grid in GRIB2 format. The products are disseminated via two mechanisms. GRIB2 files are available on the NWS FTP server. Current status of the files on the server, and descriptions of the file locations and names are available here. The files on the ftp server contain multiple grids in each file, grouped by element. The LAMP convection and lightning products are also available 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, and refer to Section C.

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


Section 0 - Indicator Section

For all LAMP Convection and Lightning 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 Significane of date in Octets 13-19
13-19 Year, Month, Day, Hour, 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 Convection and Lightning products.

Section 3 - Grid Definition Section

The LAMP Convection and Lightning guidance is presented on the 2.5-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 Octets 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 6 Spherical earth, radius in octets 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 center flag
65 64 data scan mode
66-69 25000000 Tangent Lat1
70-73 25000000 Tangent Lat2
74-77 -90000000 Latitude of south pole
78-81 0 Longitude of south pole

Section 4 - Product Definition Section

The LAMP Convection and Lightning products are packed using Product Definition Template (PDT) 4.8.  The following table lists the settings for each element.

Guidance Valid Over a Period of Time
Octet No. 2-hr Convection Probability Forecast (%) 2-hr Convection Potential Forecast
(No/Low/Med/High)
2-hr Lightning Probability Forecast (%) 2-hr Lightning
Potential Forecast
(No/Low/Med/High)
1-4 Length of section in octets
5 4 4 4 4
6-7 0 0 0 0
8-9 8 8 8 8
10 19 19 19 19
11 221 222 2 203
12 5 2 5 2
13 missing missing missing missing
14 108 108 108 108
15-16 missing missing missing missing
17 missing missing missing missing
18 1 1 1 1
19-22 hours from reference time to beginning of forecast period
23 1 1 1 1
24 0 0 0 0
25-28 0 0 0 0
29 missing missing missing missing
30 0 0 0 0
31-34 0 0 0 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 1 1 1 1
43-46 0 0 0 0
47 missing missing missing missing
48 missing missing missing missing
49 1 1 1 1
50-53 2 2 2 2
54 missing missing missing missing
55-58 missing missing 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 a decimal scale factor of 0 for all elements.

 


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Page Last Modified: December 23, 2013. 23:24 UTC