GRIB2 Encoding Details for the National Weather Service Digital Forecast Database


General Information

Background

The National Weather Service (NWS) is creating a National Digital Forecast Database (NDFD) which will contain gridded forecasts of several weather elements. In general, the weather parameters in the NDFD will be ground-based, sensible weather elements. The forecast grids that comprise the NDFD will come from multiple sources, including the NWS' Weather Forecast Offices(WFO) and the National Centers for Environmental Prediction (NCEP). The World Meteorological Organization (WMO) has adopted Edition 2 of the GRIB code as a standard for sharing GRIdded Binary data. GRIB, Edition 2 (GRIB2) will be involved in the NDFD in two ways. GRIB2 will be one of the primary formats used to transmit NDFD data to NWS customers and partners.

The purpose of this document is to describe, in detail, the techniques that will be used to encode NWS forecasts into NDFD GRIB2 bulletins. When dealing with a code as general and as flexible as GRIB2, one often encounters multiple, plausible ways to accomplish the encoding task. It is hoped that this document will clarify the many decisions made during the creation of the NDFD.

In summer of 2011, NDFD will begin making experimental CONUS GRIB2 files available that contain finer spatial resolution (2.5 km) and higher temporal resolution ( 1-hr, for Days 1-3) grids.

References

This document will assume that the reader has access to and a working knowledge of the WMO publication FM 92-XII GRIB General Regularly-distributed Information in Binary Form. NCEP WMO GRIB2 documentation should provide access to a version that has been formatted for web access.

The NWS has created an NDFD information web page. There you will find the latest news regarding NDFD plans and recent developments. In addition, MDL developers have written software that may be downloaded and used for accessing and decoding NDFD GRIB2 files from the NWS Telecommunications Gateway (NWSTG). To obtain the latest version of this software, see the MDL Degrib Page.

File, and Bulletin Structure

A single file will contain multiple GRIB2 bulletins. One file will contain multiple forecast projections for a given weather element covering a specific geographic region. There are NDFD grids available for the lower 48 states (CONUS), 16 different CONUS sub-sectors, Puerto Rico, Hawaii, Guam, and Alaska. For Tropical Prediction Center grids, there are two additional domains. One domain covers the area defined by NCEP's AWIPS 227 grid. The other domain covers the Northern Pacific, as defined by NCEP's AWIPS 204 grid.

The NDFD Oceanic domain covers a large area of the world's surface, and also contains forecast data provided by the Tropical Analysis and Forecast Branch of the National Hurricane Center, as well as the Ocean Prediction Center.

See National Digital Forecast Database (NDFD) Reference for a detailed list of geographic sectors, filenames, and WMO header information with regards to NDFD data.

GRIB2 files for a given element and region will be split into two files, one containing the forecast grids for the period Day 1 through Day 3, the other containing the forecast grids for the period Day 4 through Day 7. These files are located in different directories at the NWSTG FTP download site.

Every NDFD GRIB file begins with a flag field separator of the format:

****nnnnnnnnnn****\lf
 

where the "nnnnnnnnnn" is the size in bytes of the file, (minus the separator), right justified with leading zeroes, and with a trailing "\lf". The "\lf" character represents a single octet with the decimal value of 10. The size of the Flag field separator is 19 bytes.

Following the flag field separator is a WMO "super header". Check the NDFD WMO Heading Reference for the specific format of NDFD WMO headers. The WMO super header is 21 bytes long, the trailing "\cr\cr\lf" inclusive. The "\cr" character represents a single octet with the decimal value of 13. Immediately following the super header is another flag field separator for the first GRIB2 bulletin in the file. It contains the size of the bulletin to follow.

The bulletin itself begins with a WMO header. Again, refer to the link above to get detailed information regarding the format of the header. The header contains the valid time of the GRIB2 bulletin. The WMO header is also 21 bytes long, the trailing "\cr\cr\lf" inclusive. Following the header is the packed GRIB2 grid. It begins with the ASCII text "GRIB" and ends with the ASCII text "7777". The packed data contains all the GRIB2 sections for that grid, as well as the packed grid.

Here's an example of the file format (individual components are bracketed with "< >"):

<file flag field separator\lf> 
<WMO super header\cr\cr\lf> 
<bulletin 1 flag field separator\lf> 
<WMO header 1 for bulletin\cr\cr\lf> 
<"GRIB"packed data7777><bulletin 2 flag field separator\lf> 
<WMO header 2 for bulletin\cr\cr\lf> 
<"GRIB"packed data7777><bulletin 3 flag field separator\lf> 
. 
. 
. 
<WMO header nn for bulletin\cr\cr\lf> 
<"GRIB"packed data7777>

Octet Contents (Section 1-4)

(See grib_design2 for Sections 5-8)

The sections that follow list the contents of the GRIB2 bulletin, octet by octet. When contents are described as "Missing," all bits are set to "1" in accordance with regulation 92.1.4. When contents are described by a number, that number will be stored in the apprpriate octet.

Section 0--Indicator Section

Octet No. Contents
1-4 "GRIB"
5-6 0
7 0 - for Meteorological Products, 2 - for Land Surface Products, 10 - for Oceanographic Products
8 2
9-16 Total length of GRIB message in octets (including Section 0)

Section 1--Identification Section

In Section 1, octets 13-19 contain the reference time for the GRIB bulletin. The NDFD is currently produced once an hour. The reference time in Section 1 represents the day/hour of the current NDFD production cycle.

Octet No. Contents
1-4 21
5 1
6-7 8
8-9 Missing
10 1
11 0 - Value will be used to designate the version number of the GRIB2-encoding software that produced the bulletin.  When changes to this published format occur, this version number will be updated.
12 1
13-14 Year (4 digits)
15 Month
16 Day
17 Hour
18 Minute (*Note - For NDFD mid-hour update issuances, Octet 18 will be "30". Otherwise it will be "0".)
19 Second
20 0 or 1 - depending on the operational status of the encoded NDFD product (0 = operational, 1 = operational TEST)
21 1

Section 2--Local Use Section

Certain weather elements have provided particular challenges in encoding them in GRIB2. Using Section 2 to encode various forms of metadata provides one solution. For the NDFD elements Weather ("Wx"), and Hazards, MDL GRIB2 encoding software uses the Local Use section for packing metadata unique to each grid. At this time, for parameters other than Wx and Hazards, the Local Use section is omitted.

Grids of these 2 elements are stored as two distinct entities. The first entity is a grid of small integer values that will generally store very compactly in Section 6. The second entity is a series of null-terminated strings of ASCII characters called keys (either Wx or Hazard keys). The integers on the weather grid serve as indices, each pointing to one of the unique keys in the series. Each key is comprised of one or more subkeys, separated by a caret "^".

The metadata packed in the Local Use Section for the Wx and Hazard elements is a lookup table. The ASCII characters are loaded, one per octet, and then compressed using the Simple Packing Scheme for integers defined for Section 5. The Simple Packing Scheme treats the set of keys as an integer array. Each integer in the array is a decimal representation that corresponds to an ASCII character. For instance, the integer 65 translates to the ASCII character "A". The null character is represented by the integer 0, so that whenever a 0 is encountered in the array, it marks the ending of a unique key. The tables that follow show the specific contents of the Weather keys/subkeys and Hazard keys/subkeys.

Octet No. Contents
1-4 Length of section in octets (nn)
5 2
6 1 - Simple packing flag
7-nn The Weather/Hazard keys needed to translate the contents the grid, packed using the Simple Packing scheme

Weather Keys and Subkeys

A weather subkey has can have up to five parts, each part separated by colons ":". The parts are:

  • one weather type code. See Weather Type Codes, below.
  • one coverage/probability code. See Coverage/probability Codes, below.
  • one intensity code. See Intensity Codes, below.
  • one visibility code. See Visibility Codes, below.
  • zero or more attribute codes, separated by commas ",". See Attribute Codes, below.
Code Meaning Code Meaning
<NoWx> No Weather T Thunder
A Hail R Rain
RW Rain Showers L Drizzle
ZR Freezing Rain ZL Freezing Drizzle
S Snow SW Snow Showers
IP Ice Pellets (sleet) F Fog
H Haze BS Blowing Snow
K Smoke BD Blowing Dust
FR Frost BN Blowing Sand
IF Ice Fog IC Ice Crystals
ZF Freezing Fog ZY Freezing Spray
VA Volcanic Ash WP Water Spouts

Coverage/probability Codes

Code Meaning Code Meaning
<NoCov> No Coverage/probability Iso Isolated
Sct Scattered Num Numerous
Wide Widespread Ocnl Occasional
SChc Slight Chance Chc Chance
Lkly Likely Def Definite
Patchy Patchy Areas Areas of
Brf Brief Pds Periods of
Frq Frequent Inter Intermittent

Intensity Codes

Code Meaning Code Meaning
<NoInten> No Intensity -- Very Light
- Light m Moderate
+ Heavy    

Visibility Codes

The following visibility codes may appear in WFO-generated GRIB2 bulletins.  The units are statute miles:  <NoVis>, 0SM, 1/4SM, 1/2SM, 3/4SM, 1SM, 11/2SM, 2SM, 21/2SM, 3SM, 4SM, 5SM, 6SM, P6SM.

Attribute Codes

Code Meaning Code Meaning
FL Frequent Lightning GW Gusty Winds
HvyRn Heavy Rain DmgW Damaging Winds
SmA Small Hail LgA Large Hail
OLA on Outlying Areas OBO on Bridges and Overpasses
OGA on Grassy Areas OR Or
Dry Dry Primary Highest Ranking
Mention Include Unconditionally TOR Tornado
Mx Mixture    

Size Limitations for NDFD National Grids 

There is no (practical) limit to the number of weather keys, subkeys, etc.  For NDFD grids that are national mosaics of WFO-generated grids, the following limitations will be applied:
Item Maximum number that will be present
Weather Attributes in a Weather Subkey 5
Weather Subkeys in a Weather Key 5

Weather Key Examples

Sample Weather Key Meaning
Sct:SW:-:<NoVis>: Light scattered snow showers
Ocnl:R:-:<NoVis>:^S:Ocnl:-:<NoVis>:^
SChc:ZR:-:<NoVis>:
Occasional light rain and snow, with a slight chance of light freezing rain
Wide:FR:-:<NoVis>:OLA Widespread light frost in the outlying areas
<NoWx>:<NoCov>:<NoInten>:<NoVis>: No weather
Sct:RW:-:<NoVis>:^T:Iso:m:<NoVis>: Scattered light showers with isolated moderate thunderstorms
Sct:T:+:<NoVis>:DmgW,LgA Scattered severe thunderstorms with damaging winds and large hail

Hazard Keys and Subkeys

A hazard key has two parts, separated by a  "."
The parts are:
  • a 2 letter phenomenon code.  This could be something like "HW" (for High Wind), or "SV" (for Severe Thunderstorm).
  • a 1 letter signifucance code.  This could be either "Y" (Advisory), "S" (Statement), "A" (Watch), or "W" (Warning).
 

Section 3--Grid Definition Section

Section 3 will vary depending upon the map projection the grid is defined.  A table listing more detailed information for each NDFD geographic region (CONUS, CONUS subsectors, Puerto Rico, Hawaii, Guam, Alaska) can be found here.  Latitude and longitude values are encoded in 10 -6 degrees.  All longitudes are east.

Lambert Conformal (includes CONUS and CONUS subsectors)

Octet No. Contents
1-4 81 - Length of section in octets (nn)
5 3
6 0
7-10 Number of data points (Nx * Ny
11 0
12 0
13-14 30 - template number
15 1
16 0
17-20 6371200 - Radius of the earth
21 0
22-25 0
26 0
27-30 0
31-34 Nx - number of points along the X-axis.   (Nx values for all Lambert Conformal NDFD grids)
35-38 Ny - number of points along the Y-axis   (Ny values for all Lambert Conformal NDFD grids)
39-42 La1 - latitude of first grid point   (La1 values for all Lambert Conformal NDFD grids)
43-46 Lo1 - longitude of first grid point   (Lo1 values for all Lambert Conformal NDFD grids)
47 0
48-51 25,000,000 - Latitude where grid spacing is defined
52-55 265,000,000 - Orientation longitude
56-59 2,539,703- Dx, X-direction grid length (NDFD GRIB2 files with the old resolution of 5,079,406 are still available experimentally)
60-63 2,539,703- Dy, Y-direction grid length (NDFD GRIB2 files with the old resolution of 5,079,406 are still available experimentally)
64 0
65 80 - Scanning Mode
66-69 25,000,000 - Latin1, first secant latitude
70-73 25,000,000 - Latin2, second secant latitude
74-77 -90,000,000 - Latitude of southern pole 
78-81 0 - Longitude of southern pole

Polar Stereographic (Alaska)

Octet No. Contents
1-4 65 - Length of section in octets (nn)
5 3
6 0
7-10 Number of data points (Nx * Ny)
11 0
12 0
13-14 20 - template number
15 1
16 0
17-20 6371200 - Radius of the earth
21 0
22-25 0
26 0
27-30 0
31-34 Nx - number of points along the X-axis   ( Nx values for all Polar Stereographic NDFD grids)
35-38 Ny - number of points along the Y-axis   ( Ny values for all Polar Stereographic NDFD grids)
39-42 La1 - latitude of first grid point ( La1 values for all Polar Stereographic NDFD grids)
43-46 Lo1 - longitude of first grid point   ( Lo1 values for all Polar Stereographic NDFD grids)
47 0
48-51 60,000,000 - LaD, Latitude where mesh length defined
52-55 210,000,000 - LoV, Orientation longitude
56-59 5,953,125 - Dx, X-direction grid length
60-63 5,953,125 - Dy, Y-direction grid length
64 0 - Projection center flag
65 80 - Scanning mode

Mercator (includes Puerto Rico, Hawaii, Guam, and Oceanic domains)

Octet No. Contents
1-4 72 - Length of section in octets (nn)
5 3
6 0
7-10 Number of data points   (Nx * Ny)
11 0
12 0
13-14 10 - template number
15 1
16 0
17-20 6371200 - Radius of the earth
21 0
22-25 0
26 0
27-30 0
31-34 Nx - number of points along the X-axis   ( Nx values for all Mercator NDFD grids)
35-38 Ny - number of points along the Y-axis   ( Ny values for all Mercator NDFD grids)
39-42 La1 - latitude of first grid point   ( La1 values for all Mercator NDFD grids)
43-46 Lo1 - longitude of first grid point   ( Lo1 values for all Mercator NDFD grids)
47 0
48-51 LaD - latitude where mesh length is defined   ( LaD values for all Mercator NDFD grids)
52-55 La2 - latitude of last gridpoint   ( La2 values for all Mercator NDFD grids)
56-59 Lo2 - longitude of last gridpoint   ( Lo2 values for all Mercator NDFD grids)
60 80 - Scanning mode
61-64 0.0000 - Orientation angle of the grid
65-68 2,500,000 - Di, longitudinal direction grid length - (Exception: Puerto Rico = 1,250,000, and Oceanic = 10,000,000)
69-72 2,500,000 - Dj, latitudinal direction grid length - (Exception: Puerto Rico = 1,250,000, and Oceanic = 10,000,000)

Section 4--Product Definition Section

Section 4 will vary from one weather element to the next.  The formats for the various elements are detailed in the following sections:

Maximum Temperature (MaxT), Minimum Temperature (MinT), Maximum Relative Humidity (MaxRH), Minimum Relative Humidity (MinRH)

Octet No. Contents
1-4 58 - Length of section in octets (nn)
5 4
6-7 0
8-9 8
10 0
11 4 for MaxT
5 for MinT
27 for MaxRH
198 for MinRH
12 2
13 0
14 0
15-16 255
17 Missing
18 Either 0 or 1.
Top of the hour issuance times will have forecast projection time specified in hours (1)
Mid-hour update issuances will have forecast projection time specified in minutes (0)
19-22 Time interval from reference time to beginning of the valid period (in units specified by Octet 18)
23 1
24 0
25-28 0
29 Missing
30 0
31-34 Missing
35-36 Year of end of the valid period in GMT.
37 Month of end of the valid period in GMT. 
38 Day of end of the valid period in GMT.
39 Hour of end of the valid period in GMT.
40 Minute of end of the valid period in GMT.
41 Second of end of the valid period in GMT.
42 1
43-46 0
47 2 for Max,  3 for Min
48 2
49 1
50-53 12
54 1
55-58 0

Twelve-hour Probability of Precipitation (PoP12)

Octet No. Contents
1-4 71 - Length of section in octets (nn)
5 4
6-7 0
8-9 9
10 1
11 8
12 2
13 0
14 0
15-16 Missing
17 Missing
18 Either 0 or 1.
Top of the hour issuance times will have forecast projection time specified in hours (1)
Mid-hour update issuances will have forecast projection time specified in minutes (0)
19-22 Time interval from reference time to beginning of the valid period (in units specified by Octet 18)
23 1
24 0
25-28 0
29 Missing
30 Missing
31-34 Missing
35 Missing
36 Missing
37 1
38 Missing
39-42 Missing
43 3
44-47 254
48-49 Year of end of PoP12 valid period in GMT.
50 Month of end of PoP12 valid period in GMT.
51 Day of end of PoP12 valid period in GMT.
52 Hour of end of PoP12 valid period in GMT.
53 Minute of end of PoP12 valid period in GMT.
54 Second of end of PoP12 valid period in GMT.
55 1
56-59 0
60 1
61 Missing
62 1
63-66 12
67 1
68-71 0

Temperature, Dew point, Sky, Wind Speed, Wind Direction, Wave Height, Weather, Apparent Temperature, Relative Humidity, Wind Gust, Hazards, Haines Index

Octet No. Contents
1-4 34 - Length of section in octets (nn)
5 4
6-7 0
8-9 0
10 Parameter Category (FM 92 GRIB, Code Table 4.1) See table below for specific values
11 Parameter Number (FM 92 GRIB, Code Table 4.2) See table below for specific values
12 2
13 0
14 0
15-16 255
17 Missing
18 Either 0 or 1
Top of the hour issuance times will have forecast projection time specified in hours (1)
Mid-hour update issuances will have forecast projection time specified in minutes (0)
19-22 Forecast projection (in units specified by Octet 18)
23 1
24 0
25-28 0
29 0
30 -1
31-34 Missing

Parameter Categories and Parameter Numbers for Temperature, Dew point Temperature, Sky, Wind Speed, Wind Direction, Wave Height, Weather, Apparent Temperature, Relative Humidity, Wind Gust, Hazards, Haines Index

Parameter Name Category Number
Temperature 0 0
Dew point Temperature 0 6
Sky 6 1
Wind Speed 2 1
Wind Direction 2 0
Wave Height (see Note 1) 0 5
Weather 1 192
Apparent Temperature 0 193
Relative Humidity 1 1
Wind Gust 2 22
Hazards 19 217
PPI (Precipitation Potential Index) 1 193

Note 1: Wave Height is defined as an Oceanographic Product in Section 0 (Indicator Section, octet 7 = 10).

QPF, Snow Amount, Ice Accumulation, Daily FRET, Daily FRET Departure and Total Weekly FRET

Octet No. Contents
1-4 58 - Length of section in octets (nn)
5 4
6-7 0
8-9 8
10 1
11 6     for Daily FRET, Daily FRET Departure, and Total Weekly FRET
8     for QPF
29   for Snow Amount
227 for Ice Accumulation
12 2
13 0
14 0
15-16 255
17 Missing
18 Either 0 or 1.
Top of the hour issuance times will have forecast projection time specified in hours (1)
Mid-hour update issuances will have forecast projection time specified in minutes (0)
19-22 Time interval from reference time to beginning of the valid period (in units specified by Octet 18)
23 1
24 0
25-28 0
29 Missing
30 -1
31-34 Missing
35-36 Year of end of valid period in GMT. 
37 Month of end of valid period in GMT.
38 Day of end of valid period in GMT.
39 Hour of end of valid period in GMT.
40 Minute of end of valid period in GMT.
41 Second of end of valid period in GMT. 
42 1
43-46 0
47 10 for Daily FRET Departure
1 for all others
48 2
49 1
50-53 6     for QPF, Snow Amount, and Ice Accumulation
24   for Daily FRET and Daily FRET Departure
168 for Total Weekly FRET
54 1
55-58 0

Tropical Wind Speed Probabilities (Incremental and Cumulative) greater than 34, 50, and 64 knots - from Tropical Prediction Center

Octet No. Contents
1-4 71 - Length of section in octets (nn)
5 4
6-7 0
8-9 9
10 2 - Momentum
11 1 - Wind Speed
12 2
13 0
14 0
15-16 Missing
17 Missing
18 Either 0 or 1.
Top of the hour issuance times will have forecast projection time specified in hours (1)
Mid-hour update issuances will have forecast projection time specified in minutes (0)
19-22 Time interval from reference time to beginning of the valid period (in units specified by Octet 18)
23 103 - specified height above ground level
24 0
25-28 10 (meters)
29 Missing
30 0
31-34 0
35 Missing
36 Missing
37 1 - probability of event above upper limit
38 0
39-42 0
43 3 - scale factor of upper limit
44-47 17491 (m/s), or 25722 (m/s), or 32924 (m/s) - corresponds to 34, 50, and 64 knots 
48-49 Year of end WindSpd Prob valid period in GMT
50 Month of end WindSpd Prob valid period in GMT
51 Day of end WindSpd Prob valid period in GMT
52 Hour of end WindSpd Prob valid period in GMT
53 Minute of end WindSpd Prob valid period in GMT
54 Second of end WindSpd Prob valid period in GMT
55 1
56-59 0
60 1
61 2 - (incremental probability), 192 - (cumulative probability)
62 1 - type of time increment between successive fields (hours)
63-66 6 - (incremental probability),  variable number of hours from the reference time to the end time of the valid period - cumulative probability)
67 1
68-71 0

Hazard Probabilities - from Storm Prediction Center (Includes Probabilities of Tornado, Hail, and Damaging Winds, Probabilities of Extreme Tornado, Hail, and Damaging Winds, Total Probability of Severe, and Extreme Severe Thunderstorms

Octet No. Contents
1-4 71 - Length of section in octets (nn)
5 4
6-7 0
8-9 9
10 Parameter Category (FM 92 GRIB, Code Table 4.1) See Hazard Parameter Table below for specific values
11 Parameter Number (FM 92 GRIB, Code Table 4.2) See Hazard Parameter Table below for specific values
12 2
13 0
14 0
15-16 255
17 255
18 Either 0 or 1.
Top of the hour issuance times will have forecast projection time specified in hours (1)
Mid-hour update issuances will have forecast projection time specified in minutes (0)
19-22 Time interval from reference time to beginning of the valid period (in units specified by Octet 18)
23 1
24 0
25-28 0
29 255
30 -1
31-34 -1
35 255
36 255
37 1
38 -1
39-42 -1
43 0
44-47 0
48-49 Year of end of valid period in GMT. 
50 Month of end of valid period in GMT.
51 Day of end of valid period in GMT.
52 Hour of end of valid period in GMT.
53 Minute of end of valid period in GMT.
54 Second of end of valid period in GMT. 
55 1
56-59 0
60 0
61 255
62 1
63-66 24
67 1
68-71 0

Parameter Categories and Parameter Numbers for Hazard Probabilities

Parameter Name Parameter Category Parameter No.
Probability of Tornado 19 197
Probability of Hail 19 198
Probability of Damaging Winds 19 199
Probability of Extreme Tornado 19 200
Probability of Extreme Hail 19 201
Probability of Extreme Damaging Winds 19 202
Total Probability of Severe Thunderstorms 19 203
Total Probability of Extreme Severe Thunderstorms 19 204

Categorical Outlooks - from Storm Prediction Center (includes Convective Hazard Outlook, Fire Wx Critical and Extremely Critical Areas, and Fire Wx Critical Areas for Dry Thunderstorms) and Tropical Cyclone Categorical Threats from WFOs (include Tropical Cyclone Storm Surge Threat, Tropical Cyclone Flooding Rain Threat, Tropical Cyclone Tornado Threat, and Tropical Cyclone Wind Threat)

Octet No. Contents
1-4 58 - Length of section in octets
5 4
6-7 0
8-9 8
10 Parameter Category (FM 92 GRIB, Code Table 4.1) See Categorical Outlook Parameter Table below for specific values
11 Parameter Number (FM 92 GRIB, Code Table 4.2) See Categorical Outlook Parameter Table below for specific values
12 2
13 0
14 0
15-16 255
17 255
18 Either 0 or 1.
Top of the hour issuance times will have forecast projection time specified in hours (1)
Mid-hour update issuances will have forecast projection time specified in minutes (0)
19-22 Time interval from reference time to beginning of the valid period (in units specified by Octet 18)
23 1
24 0
25-28 0
29 255
30 -1
31-34 -1
35-36 Year of end of valid period in GMT. 
37 Month of end of valid period in GMT.
38 Day of end of valid period in GMT.
39 Hour of end of valid period in GMT.
40 Minute of end of valid period in GMT.
41 Second of end of valid period in GMT. 
42 1 - SPC Outlooks
2 - Tropical Cyclone Threats
43-46 0
47 1
48 255
49 1
50-53 24
54 1
55-58 0

Parameter Categories and Parameter Numbers for Categorical Outlooks and Tropical Cyclone Threats

Parameter Name Parameter Category Parameter No.
Convective Hazard Outlook 19 194
Wx  Critical and Extremely Critical Areas 192 192
Fire  >Wx  Critical Areas for Dry Thunderstorms 192 194
Tropical Cyclone Storm Surge Threat 19 236
Tropical Cyclone Flooding Rain Threat 19 238
Tropical Cyclone Tornado Threat 19 239
Tropical Cyclone Wind Threat 19 235

Climate Outlook Probability Elements - from Climate Prediction Center (Average Temperature and Total Precip Above and Below Normal for 8-14 Day Outlook, 1 Month Outlook, and Seasonal Outlook)

Octet No. Contents
1-4 71- Length of section in octets (nn)
5 4
6-7 0
8-9 9
10 Parameter Category (FM 92 GRIB, Code Table 4.1)    0 = Temperature, 1 = Moisture
11 Parameter Number (FM 92 GRIB, Code Table 4.2)     0 = Temperature, 8 = Total Precipitation
12 2
13 0
14 0
15-16 255
17 255
18 Indicator of unit of time range - 8-14 Day Outlooks = 2 (days); Monthly and Seasonal Outlooks = 3 (months)
19-22 Time from beginning of issuance day (8-14 Day Outlooks) or issuance month (Monthly/Seasonal Outlooks) to beginning of valid period in units specified by octet 18 
23 1
24 0
25-28 0
29 255
30 -1
31-34 -1
35 255
36 2 - Total Number of forecast probabilities
37 3 - Probability type
38 0
39-42 0
43 0
44-47 0
48-49 Year of end of valid period in GMT. 
50 Month of end of valid period in GMT.
51 Day of end of valid periodin GMT.
52 Hour of end of valid period in GMT.
53 Minute of end of valid period in GMT.
54 Second of end of valid period in GMT. 
55 1
56-59 0
60 0
61 255
62 Indicator of unit of time for time range over which statistical processing is done.   8-14 Day Outlooks = 2 (days); Monthly and Seasonal Outlooks = 3 (months)
63-66 Length of time range over which statistical processing is done.  8-14 Day Outlooks = 6 (days); Monthly Outlooks = 1 (month); Seasonal Outlooks = 3 (months)
67 1
68-71 0