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 here 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

LAMP