OUTLINE OF WMO BULLETIN HEADERS
USED WITH
NCEP GRIB
Revised 04/21/2006
Red text depicts changes made since 04/07/2006
WMO BULLETIN HEADER

The WMO abbreviated heading is used to identify the NCEP GRIB messages; however, it is not a complete description of their content. The user is cautioned against using the header as the sole determiner of the record content; one should, of course, rely on the Product Definition Section for that purpose. Note: In the following, a hexadecimal number is enclosed in parentheses followed by the designation "hex". The information needed to identify the NCEP product is contained in 21 octets. The characters are encoded using the CCITT-ITA No. 5, also known (in the US) as ASCII characters, and are defined as follows:
Octet | Header Content
1 | The character 'H' for GRIB bulletins sent to the NWS Family of Services, used for the WAFS program, and for general International Exchange or The character ‘O’ for oceanographic GRIB bulletins intended for general International and National Exchange and for use in the NWS AWIPS program or The characters 'L', 'M', 'Y' or 'Z' for meteorological GRIB bulletins intended for the NWS AWIPS program.
2 | A letter character specifying the type parameter as shown in Table A.1.
3 | A letter character specifying the grid area as defined in Table A.2.
4 | A letter or numeric character indicating the time difference between the reference time and valid time of the data as listed in Table A.3, i.e., the forecast length.
5-6 | Numeric characters as defined in Table A.4. Usually the pressure level, sometimes just a sequence number. Some values have special level or layer meanings.
7 | Blank (20)hex
8-11 | Four characters identifying the originating center. The first three characters are always ‘KWB’ for NCEP-produced messages. The last character is a letter specifying the NCEP model as defined in Table A.5.
12 | Blank (20)hex
13-14 | Two numeric characters providing the reference day of the month (01-31) of the data.
15-18 | Four numeric characters providing the reference hour and minute of the data.
19-22 | Four OPTIONAL characters: one blank (20)hex, then 'Pxx', where xx=AA, AB, AC ... AY,AZ, BA, BB, BC ... etc. Used to indicate sequential parts of a very long message that has been subdivided. The last part of the message will have xx=Zn, where n is the next letter in the appropriate sequence. Example: a five part message would have the parts indicated by PAA, PAB, PAC, PAD, PZE.
19-21 or 23-25 | Two ASCII carriage returns and a line feed, (0D0D0A)hex.
The first six characters are commonly referred to as: T1 T2 A1 A2 ii In summary... Generic Meaning of T1 T2 A1 A2 ii: T1: Type of bulletin: "H" for GRIB messages for Family of Services, WAFS, and International Exchange; “O” and "E" for Oceanographic GRIB messages for National and International Exchange and for AWIPS GRIB messages; or "L", "M", "Y" or "Z" for AWIPS GRIB messages T2: Type of data/parameter A1: Grid A2: Analysis or forecast hour ii: Numeric. Usually the pressure level, sometimes just a sequence number. Some values have special level or layer meanings. In the following tables, the columns headed AWIPS are augmentations to the common Family of Services (FOS), National, and International Exchange variables. FOS, National and International GRIB messages (with H as the initial character) draw upon the left hand columns only. National, International, and AWIPS GRIB messages (with O as the initial character) draw upon the middle column only. AWIPS GRIB messages (with Y or Z as the initial character) use letters from both the left and right columns. If each column contains entries for the same designator, the T1 character (H, O, L, M, Y, or Z) indicates which entry to use.

TABLE A.1 TYPE PARAMETERS - T2
(Header Octet 2)

Designator | PARAMETER
| FOS & International (H) | AWIPS (E or O) | AWIPS (L, M, Y or Z)
A |  | U-wind/current component | Cloud of non-conforming ICWF* parameters
B |  | V-wind/current component | Vertical Wind Shear
C | Vorticity | Total Significant Wave Height | Vorticity
D |  | Depth | Probability Parameters
E | Total Precipitation | Ice Concentration | Total Precipitation
F | Long Wave Radiation | Ice Thickness | Precipitable Water
G | Convective Precipitation | Ice Drift | Convective Precipitation
H | Height (geopotential) | Ice Growth | Height (geopotential)
I |  | Ice Convergence | Non-Convective Precipitation
J | Significant Wave Height | Period of Spectral Peak of the Ocean Waves | Precipitation Rate
K | Primary Wave Period | Direction of Spectral Peak of the Ocean Waves | Visibility
L | Primary Wave Direction | Height of Significant Wind Waves | Soil Parameters
M | Secondary Wave Period | Mean Period of Wind Waves | Catagorical Parameters (yes/no)
N | Secondary Wave Direction | Mean Direction of Wind Waves | Wind Speed or Gust
O | Vertical Velocity | Height of Significant Swell Waves | Vertical Velocity
P | Pressure | Mean Direction of Swell Waves | Pressure
Q |  | Wind Speed | Stability Index
R | Relative Humidity | Wind Direction | Relative Humidity
S | Snow | Salinity | Snow
T | Air Temperature | Ocean Temperature |
U | U Wind Component | Vessel Icing | U Wind Component
V | V Wind Component | Visibility | V Wind Component
W |  | Ocean Temperature Warming | CAPE
X | Surface Lifted Index | Mixed Data | Surface Parameters
Y | UV Index | Mean Period of Swell Waves | CIN
Z | Refer to GRIB PDS | Refer to GRIB PDS | Helicity

* Surface wind direction, surface wind speed, surface dew-point temperature,
maximum surface temperature, and minimum surface temperature
TABLE A.2 GRID DESIGNATOR - A1
(Header Octet 3)

Designator | Grid Number (See Table B)
| FOS and International (H) | AWIPS (O) | AWIPS (L, M, Y or Z)
A | 21 | 228 - 2.5x2.5 deg lat/lon global | 201 - 381 km Northern Hemisphere
B | 22 | 218 - 12-km CONUS | 218 - 12-km CONUS
C | 23 | 219 - N. Hemisphere High Res | 175 - 10 km lat/lon Guam
D | 24 | 220 - S. Hemisphere High Res | 130 - 13-km CONUS
E | 25 | 221 - N. American High Res | 185 - 12 km CONUS (DGEX)
F | 26 | 229 - 1.0x1.0 deg lat/lon global | 186 – 12 km Alaska (DGEX)
G | 50 | 230 - 0.5x0.5 deg lat/lon global | 160 - 47.5 km Alaska NPS
H |  | 231 - 0.5x0.5 deg lat/lon N.H. | 213 - 95 km CONUS
I | 37 | 232 - 1.0x1.0 deg lat/lon N.H. | 202 - 191 km CONUS
J | 38 | 233 - 1.25x1.00 deg lat/lon global | 203 - 191 km Alaska
K | 39 | 234 - 0.25x0.25 deg lat/lon ECGM regional | 204 - 160 km Hawaii
L | 40 | 235 - 0.5x0.5 deg lat/lon global | 205 - 191 km Puerto Rico
M | 41 | 238 - Western North Atlantic lat/lon | 227 - 5 km CONUS
N | 42 | 239 - Alaska Regional lat/lon | 207 - 95 km Alaska
O | 43 | 244 - North Atlantic lat/lon | 254 - 40 km Mercator Pacific Region
P | 44 | 251 - COFS lat/lon | 237 - 32 km Puerto Rico
Q |  | 253 - Eastern North Pacific lat/lon | 211 - 80 km CONUS
R |  | 212 - 40 km CONUS | 212 - 40 km CONUS
S |  | 253 - Eastern North Pacific lat/lon | 242 - 11.25 km Alaska
T | 61 | 214 - 48 km Alaska | 161 - 0.5 degree lat/lon Puerto Rico
U | 62 | 215 - 20 km CONUS | 215 - 20 km CONUS
V | 63 | 216 - 45 km Alaska | 216 - 45 km Alaska
W | 64 | 173 - 1/12 degree global lat/lon | 236 - 40 km CONUS
X |  |  | 243 - 0.4 degree NE Pacific
Y |  |  | 217 - 22 km Alaska
Z | Refer to GRIB PDS

Table A.3 FORECAST HOUR DESIGNATOR
(Header Octet 4)

DESIGNATOR | FORECAST HOUR
FOS, International (H) and AWIPS (L or Y) | National, International (O) and AWIPS (E or O) | AWIPS (M or Z)
Octet 8-11 = KWBM | Octet 8-11 = KWBJ
A | 00 hour analysis | 00 hour analysis | 00 hour analysis | 02 hour fcst
B | 06 hour fcst | 12 hour fcst | 03 hour fcst | 03 hour fcst
C | 12 hour fcst | 24 hour fcst | 06 hour fcst | 04 hour fcst
D | 18 hour fcst | 36 hour fcst | 09 hour fcst | 08 hour fcst
E | 24 hour fcst | 48 hour fcst | 12 hour fcst | 09 hour fcst
F | 30 hour fcst | 60 hour fcst | 15 hour fcst | 10 hour fcst
G | 36 hour fcst | 72 hour fcst | 18 hour fcst | 14 hour fcst
H | 42 hour fcst | 84 hour fcst | 21 hour fcst | 15 hour fcst
I | 48 hour fcst | 96 hour fcst | 24 hour fcst | 16 hour fcst
J | 60 hour fcst | 108 hour fcst | 30 hour fcst | 20 hour fcst
K | 72 hour fcst | 120 hour fcst | 36 hour fcst | 21 hour fcst
L | 84 hour fcst | 144 hour fcst | 42 hour fcst | 27 hour fcst
M | 96 hour fcst | 168 hour fcst | 48 hour fcst | 54 hour fcst
N | 108 hour fcst | 192 hour fcst | 60 hour fcst | 66 hour fcst
O | 120 hour fcst | 216 hour fcst | 72 hour fcst | 33 hour fcst
P | 132 hour fcst | 240 hour fcst | 84 hour fcst | 39 hour fcst
Q | 144 hour fcst | 264 hour fcst | 96 hour fcst | 45 hour fcst
R | 156 hour fcst | 288 hour fcst | 120 hour fcst | 51 hour fcst
S | 168 hour fcst | 312 hour fcst | 132 hour fcst | 57 hour fcst
T | 180 hour fcst | 336 hour fcst | 144 hour fcst | 78 hour fcst
U | 192 hour fcst | 360 hour fcst | 156 hour fcst | 90 hour fcst
V | 204 hour fcst | 384 hour fcst | 168 hour fcst | 102 hour fcst
W | 216 hour fcst | - | - | 114 hour fcst
X | 228 hour fcst | - | 54 hour fcst |
Y | 240 hour fcst | - | 66 hour fcst | -
Z | Refer to GRIB PDS | Refer to GRIB PDS | 108 hour fcst | Refer to GRIB PDS

The WMO headings for Eta model products generated on grid 237 (Puerto Rico) and RUC model products generated on grid 236 (CONUS 40 km)
and grid 130 (CONUS 13 km) use a special table for the FORECAST HOUR DESIGNATOR - A2 (Header Octet 4).
This table is defined as follows:

DESIGNATOR | FORECAST HOUR AWIPS (Y or Z) | DESIGNATOR | FORECAST HOUR AWIPS (Y or Z)
A | 00 Hour Analysis | N | 18 Hour Forecast
B | 01 Hour Forecast | O | 24 Hour Forecast
C | 02 Hour Forecast | P | 30 Hour Forecast
D | 03 Hour Forecast | Q | 36 Hour Forecast
E | 04 Hour Forecast | R | 42 Hour Forecast
F | 05 Hour Forecast | S | 48 Hour Forecast
G | 06 Hour Forecast | T | 60 Hour Forecast
H | 07 Hour Forecast | U | 72 Hour Forecast
I | 08 Hour Forecast | V | 84 Hour Forecast
J | 09 Hour Forecast | W | 96 Hour Forecast
K | 10 Hour Forecast | X | 108 Hour Forecast
L | 11 Hour Forecast | Y | 120 Hour Forecast
M | 12 Hour Forecast | Z | Refer to GRIB PDS

The above table is maintained by the NWS Office of the Chief Information Officer and can be found online at:
http://www.weather.gov/tg/tablec10.html
TABLE A.4 LEVEL DESIGNATORS - ii
(Header Octets 5 and 6)
The following version of Table A.4 contains changes implemented by the WMO on November 3, 1993. Unless indicated in Table A.4 below, the designator given is the hundreds and tens digits of the hPa level in the atmosphere, e.g. 70=700hPa; 03=30hPa, etc.

DESIGNATOR | LEVEL or LAYER
99 | 1000 hPa
98 | Air Properties at the Surface of Earth
97 | Level of the Tropopause
96 | Level of the Maximum Wind
94 | Level of the 0 deg. C isotherm
93 | 975 hPa
92 | 925 hPa
91 | 875 hPa
89 | Any Parameter Reduced to Sea Level
88 | Land/Water Properties at the Surface of the Earth/Ocean
87 | 1000-500 hPa thickness
86 | Boundary Layer
82 | 825 hPa
77 | 775 hPa
74 | Cloud Top Level
73 | Cloud Bottom Level (high, med, or low)
72 | 725 hPa
67 | 675 hPa
62 | 625 hPa
57 | 575 hPa
52 | 525 hPa
47 | 475 hPa
42 | 425 hPa
37 | 375 hPa
32 | 325 hPa
27 | 275 hPa
22 | 225 hPa
17 | 175 hPa
12 | 125 hPa
01 | Refer to GRIB PDS
00 | Entire Atmosphere
Note: The following levels are used to indicate geometric height for aviation flight levels, not pressure levels
81 | 6000 ft FL (approximately 810 hPa)
73 | 9000 ft FL (approximately 730 hPa)
64 | 12000 ft FL (approximately 640 hPa)
51 | 18000 ft FL (approximately 510 hPa)

TABLE A.5 MODEL IDENTIFIERS
(Header Octet 11)
All NCEP GRIB products have a CCCC that starts with KWB(?). The fourth letter of this identifier is defined as follows.

DESIGNATOR | NCEP MODEL
A | Reserved for Future Use
B | Reserved for Future Use
C | Global Forecast System Model
D | Downscaled GFS using Eta eXtension (DGEX)
E | North American Mesoscale (NAM) Model
F | Nested Grid Model (NGM)
G | Rapid Update Cycle
H | Medium Range Forecast (MRF)
I | Sea Surface Temperature Analysis
J | Wind-Wave Forecast Model
K | Global Ensemble Forecasts
L | Regional Ensemble Forecasts
M | Ocean Models
N | Used by NDFD Program
O | Merge of Models
P | EPA/CMAQ
Q | Reserved for Future Use
R | Real Time Mesoscale Analysis / Analysis of Error
S-Y | Reserved for Future Use
Z | Refer to GRIB PDS