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 GRI dded B inary 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.
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. This link 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, follow this link.
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 this link 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 this link 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>
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.
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|
|
|
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) |
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.
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|
|
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 |
|
19 |
Second |
|
20 |
0 or 1 - depending on the operational status of the encoded NDFD product (0 = operational, 1 = operational TEST) |
|
21 |
1 |
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.
|
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|
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 |
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.
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|
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 |
|
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|||
|
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 |
|
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|||
|
Code |
Meaning |
Code |
Meaning |
|
<NoInten> |
No Intensity |
-- |
Very Light |
|
- |
Light |
m |
Moderate |
|
+ |
Heavy |
|
|
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.
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|
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 |
|
|
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:
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|
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|
Item |
Maximum number that will be present |
|
Weather Attributes in a Weather Subkey |
5 |
|
Weather Subkeys in a Weather Key |
5 |
|
|
|
|
Sample Weather Key |
Meaning |
|
Sct:SW:-:<NoVis>: |
Light scattered snow showers |
|
Ocnl:R:-:<NoVis>:^S:Ocnl:-:<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 |
A hazard key has two parts, separated by a
"."
The parts are:
A full list of Hazard keys found on NDFD grids can be found here.
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.
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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. (Click here to see Nx values for all Lambert Conformal NDFD grids) |
|
35-38 |
Ny - number of points along the Y-axis (Click here to see Ny values for all Lambert Conformal NDFD grids) |
|
39-42 |
La1 - latitude of first grid point (Click here to see La1 values for all Lambert Conformal NDFD grids) |
|
43-46 |
Lo1 - longitude of first grid point (Click here to see 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 |
5,079,406 - Dx, X-direction grid length (Click here to see Dx values for Lambert Conformal NDFD grids) |
|
60-63 |
5,079,406 - Dy, Y-direction grid length (Click here to see Dy values for Lambert Conformal NDFD grids) |
|
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 |
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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 (Click here to see Nx values for all Polar Stereographic NDFD grids) |
|
35-38 |
Ny - number of points along the Y-axis (Click here to see Ny values for all Polar Stereographic NDFD grids) |
|
39-42 |
La1 - latitude of first grid point (Click here to see La1 values for all Polar Stereographic NDFD grids) |
|
43-46 |
Lo1 - longitude of first grid point (Click here to see 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 |
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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 (Click here to see Nx values for all Mercator NDFD grids) |
|
35-38 |
Ny - number of points along the Y-axis (Click here to see Ny values for all Mercator NDFD grids) |
|
39-42 |
La1 - latitude of first grid point (Click here to see La1 values for all Mercator NDFD grids) |
|
43-46 |
Lo1 - longitude of first grid point (Click here to see Lo1 values for all Mercator NDFD grids) |
|
47 |
0 |
|
48-51 |
LaD - latitude where mesh length is defined (Click here to see LaD values for all Mercator NDFD grids) |
|
52-55 |
La2 - latitude of last gridpoint (Click here to see La2 values for all Mercator NDFD grids) |
|
56-59 |
Lo2 - longitude of last gridpoint (Click here to see 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 will vary from one weather element to the next. The formats for the various elements are detailed in the following sections:
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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 27 for MaxRH 198 for MinRH |
|
12 |
2 |
|
13 |
0 |
|
14 |
0 |
|
15-16 |
255 |
|
17 |
Missing |
|
18 |
1 |
|
19-22 |
Hours from reference time to beginning of the valid period. |
|
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 |
|
|
|
|
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 |
1 |
|
19-22 |
Hours from reference time to beginning of PoP12 valid period. |
|
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 |
|
|
|
|
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 |
1 |
|
19-22 |
Forecast projection in hours |
|
23 |
1 |
|
24 |
0 |
|
25-28 |
0 |
|
29 |
0 |
|
30 |
-1 |
|
31-34 |
Missing |
|
|
||
|
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 |
|
Haines Index (see Note 2) |
4 |
2 |
Note 1: Wave Height is defined as an Oceanographic Product in Section 0 (Indicator Section, octet 7 = 10).
Note 2: Haines Index is defined as a Land Surface Product in Section 0 (Indicator Section, octet 7 = 2).
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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 227 for Ice Accumulation |
|
12 |
2 |
|
13 |
0 |
|
14 |
0 |
|
15-16 |
255 |
|
17 |
Missing |
|
18 |
1 |
|
19-22 |
Hours from reference time to beginning of valid period. |
|
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 |
|
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 |
1 |
|
19-22 |
0 |
|
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 |
|
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 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 |
255 |
|
18 |
1 |
|
19-22 |
Hours from reference time to beginning of valid period |
|
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 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 |
|
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 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 |
255 |
|
18 |
1 |
|
19-22 |
Hours from reference time to beginning of valid period |
|
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 Name |
Parameter Category |
Parameter No. |
|
Convective Hazard Outlook |
19 |
194 |
|
Fire 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 |
|
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 |
The GRIB2 standard supports eight forms of data packing. Grids transmitted as part of the NDFD will use complex packing (Data Representation Template 5.2), and optionally, second order spatial differencing (Data Representation Template 5.3).
NDFD grids will generally contain a significant number of missing values. National mosaic grids are defined to be rectangles, and they generally extend into areas where NWS WFOs do not have forecast responsibility.
|
|
|
|
Octet No. |
Contents |
|
1-4 |
47 or 49 - Length of section in octets (nn) (47 for Template 5.2, 49 for Template 5.3) |
|
5 |
5 |
|
6-9 |
Total number of data points. |
|
10-11 |
2 or 3 |
|
12-15 |
Reference value (R) as an IEEE 32-bit floating-point value. Varies from grid to grid. |
|
16-17 |
Binary scale factor (E). Varies from weather element to weather element. See Element Encoding Characteristics Table for values. For experimental fine resolution grids….click Here. |
|
18-19 |
Decimal scale factor (D). Varies from weather element to weather element. See Element Encoding Characteristics Table for values. For experimental fine resolution grids….click Here. |
|
20 |
Number of bits used for each group reference value. |
|
21 |
1 (integer) for Weather grids; 0 (floating point) for all other weather elements. |
|
22 |
1 |
|
23 |
1 |
|
24-27 |
Primary missing value substitute. See Element Encoding Characteristics Table for values. The values in the table will appear in the GRIB2 bulletins in Section 5, but will not appear with the data in section 7. The GRIB2 standard calls for missing values to be carried as the largest value possible in a particular group. For experimental fine resolution grids….click Here |
|
28-31 |
0 |
|
32-47 |
See GRIB2 documentation. |
|
48 |
2 - Order of spatial differencing (Template 5.3 only) |
|
49 |
See GRIB2 documentation. (Template 5.3 only) |
Bit-maps will not be used in NDFD GRIB bulletins.
Missing values will appear in those grid locations where forecasts are not
valid.
|
|
|
|
Octet No. |
Contents |
|
1-4 |
6 - Length of section in octets (nn) |
|
5 |
6 |
|
6 |
255 |
|
|
|
|
Octet No. |
Contents |
|
1-4 |
Length of section in octets (nn) |
|
5 |
7 |
|
6-nn |
See GRIB2 documentation. |
|
|
|
|
Octet No. |
Contents |
|
1-4 |
"7777" |
|
|
Operational Values |
Experimental Values |
|
Dx |
5,079,406 |
2,539,703 |
|
Dy |
5,079,406 |
2,539,703 |
|
Weather Element |
Original NDFD Units |
GRIB2-encoded Units |
Binary Scale Factor CONUS 5 km |
Binary Scale Factor
- CONUS 2.5 km |
Decimal Scale
Factor CONUS 5 km |
Decimal Scale
Factor - CONUS 2.5 km |
Primary Missing
Value Substitute |
|
MaxT |
Fahrenheit |
Kelvin |
0 |
2 |
1 |
1 |
9999 |
|
MinT |
Fahrenheit |
Kelvin |
0 |
2 |
1 |
1 |
9999 |
|
PoP12 |
Percent Probability |
Percent Probability |
0 |
0 |
0 |
0 |
9999 |
|
T |
Fahrenheit |
Kelvin |
0 |
2 |
1 |
1 |
9999 |
|
Td |
Fahrenheit |
Kelvin |
0 |
2 |
1 |
1 |
9999 |
|
Sky |
Percentage |
Percentage |
0 |
0 |
0 |
0 |
9999 |
|
Wind Speed |
Knots |
ms-1 |
0 |
2 |
1 |
1 |
9999 |
|
Wind Direction |
degrees true |
Degrees true |
0 |
0 |
0 |
-1 |
9999 |
|
Weather |
N/A |
N/A |
0 |
0 |
0 |
0 |
9999 |
|
QPF |
Inches |
kgm-2 |
0 |
0 |
2 |
2 |
9999 |
|
Snow Amount |
Inches |
Meters |
0 |
0 |
3 |
3 |
9999 |
|
Wave Height |
Feet |
Meters |
0 |
0 |
1 |
1 |
9999 |
|
Apparent Temperature |
Fahrenheit |
Kelvin |
0 |
2 |
1 |
1 |
9999 |
|
Relative Humidity |
Percent |
Percent |
0 |
0 |
0 |
0 |
9999 |
|
Wind Gust |
Knots |
ms-1 |
0 |
2 |
1 |
1 |
9999 |
|
Tropical Wind Speed Probabilities |
Percent Probability |
Percent Probability |
0 |
0 |
0 |
0 |
9999 |
|
Convective Outlooks/Fire Wx Outlooks |
Categorical |
Categorical |
0 |
0 |
0 |
0 |
9999 |
|
Hazard Probabilities |
Percent Probability |
Percent Probability |
0 |
0 |
0 |
0 |
9999 |
|
Climate Outlook Probabilities |
Categorical |
Categorical |
0 |
0 |
0 |
0 |
9999 |
|
Ice Accumulation |
Inches |
kgm-2 |
0 |
0 |
2 |
2 |
9999 |
|
MaxRH |
% |
% |
0 |
0 |
0 |
0 |
9999 |
|
MinRH |
% |
% |
0 |
0 |
0 |
0 |
9999 |
|
Hazards |
N/A |
N/A |
0 |
0 |
0 |
0 |
9999 |
|
Daily FRET |
Inches |
kgm-2 |
NA |
0 |
NA |
2 |
9999 |
|
Daily FRET Departure |
Inches |
kgm-2 |
NA |
0 |
NA |
2 |
9999 |
|
Total Weekly FRET |
Inches |
kgm-2 |
NA |
0 |
NA |
2 |
9999 |
|
Tropical Cyclone Storm Surge Threat |
Categorical |
Categorical |
NA |
0 |
NA |
0 |
9999 |
|
Tropical Cyclone Flooding Rain Threat |
Categorical |
Categorical |
NA |
0 |
NA |
0 |
9999 |
|
Tropical Cyclone Wind Threat |
Categorical |
Categorical |
NA |
0 |
NA |
0 |
9999 |
|
Tropical Cyclone Tornado Threat |
Categorical |
Categorical |
NA |
0 |
NA |
0 |
9999 |
|
Haines Index |
Categorical |
Categorical |
NA |
0 |
NA |
0 |
9999 |
|
Sector Name |
Item |
Value |
|
CONUS |
|
|
|
5 km |
Nx |
1073 |
|
|
Ny |
689 |
|
|
La1 |
2019199 |
|
|
Lo1 |
2384459 |
|
CONUS |
|
|
|
2.5 km |
Nx |
2143 |
|
|
Ny |
1375 |
|
|
La1 |
2019199 |
|
|
Lo1 |
2384459 |
|
Central Great Lakes |
|
|
|
|
Nx |
173 |
|
|
Ny |
219 |
|
|
La1 |
3876136 |
|
|
Lo1 |
2715378 |
|
Central Mississippi Valley |
|
|
|
|
Nx |
197 |
|
|
Ny |
187 |
|
|
La1 |
3409910 |
|
|
Lo1 |
2646187 |
|
Central Plains |
|
|
|
|
Nx |
223 |
|
|
Ny |
187 |
|
|
La1 |
3469884 |
|
|
Lo1 |
2550276 |
|
Central Rockies |
|
|
|
|
Nx |
254 |
|
|
Ny |
185 |
|
|
La1 |
3510457 |
|
|
Lo1 |
2462040 |
|
Eastern Great Lakes |
|
|
|
|
Nx |
187 |
|
|
Ny |
192 |
|
|
La1 |
3925241 |
|
|
Lo1 |
2735126 |
|
Mid-Atlantic |
|
|
|
|
Nx |
194 |
|
|
Ny |
200 |
|
|
La1 |
3139028 |
|
|
Lo1 |
2742057 |
|
Northeast |
|
|
|
|
Nx |
187 |
|
|
Ny |
229 |
|
|
La1 |
3869834 |
|
|
Lo1 |
2812826 |
|
Northern Plains |
|
|
|
|
Nx |
252 |
|
|
Ny |
239 |
|
|
La1 |
3968270 |
|
|
Lo1 |
2546129 |
|
Northern Rockies |
|
|
|
|
Nx |
306 |
|
|
Ny |
228 |
|
|
La1 |
3944028 |
|
|
Lo1 |
2439814 |
|
Pacific Northwest |
|
|
|
|
Nx |
313 |
|
|
Ny |
212 |
|
|
La1 |
3949451 |
|
|
Lo1 |
2341168 |
|
Pacific Southwest |
|
|
|
|
Nx |
312 |
|
|
Ny |
252 |
|
|
La1 |
2926025 |
|
|
Lo1 |
2368744 |
|
Southeast |
|
|
|
|
Nx |
243 |
|
|
Ny |
201 |
|
|
La1 |
2407851 |
|
|
Lo1 |
2691026 |
|
Southern Mississippi Valley |
|
|
|
|
Nx |
199 |
|
|
Ny |
184 |
|
|
La1 |
2860611 |
|
|
Lo1 |
2640133 |
|
Southern Plains |
|
|
|
|
Nx |
314 |
|
|
Ny |
275 |
|
|
La1 |
2510639 |
|
|
Lo1 |
2528770 |
|
Southern Rockies |
|
|
|
|
Nx |
267 |
|
|
Ny |
190 |
|
|
La1 |
3031159 |
|
|
Lo1 |
2451204 |
|
Upper Mississippi Valley |
|
|
|
|
Nx |
245 |
|
|
Ny |
270 |
|
|
La1 |
3818489 |
|
|
Lo1 |
2597956 |
|
Sector Name |
Item |
Value |
|
Alaska |
|
|
|
|
Nx |
825 |
|
|
Ny |
553 |
|
|
La1 |
4053010 |
|
|
Lo1 |
1814290 |
|
Sector Name |
Item |
Value |
|
Puerto Rico |
|
|
|
|
Nx |
339 |
|
|
Ny |
227 |
|
|
La1 |
1697739 |
|
|
Lo1 |
2919721 |
|
|
La2 |
195445 |
|
|
Lo2 |
296016 |
|
|
LaD |
2000000 |
|
Hawaii |
|
|
|
|
Nx |
321 |
|
|
Ny |
225 |
|
|
La1 |
180726 |
|
|
Lo1 |
1984750 |
|
|
La2 |
230877 |
|
|
Lo2 |
206131 |
|
|
LaD |
2000000 |
|
Guam |
|
|
|
|
Nx |
193 |
|
|
Ny |
193 |
|
|
La1 |
1234988 |
|
|
Lo1 |
1436865 |
|
|
La2 |
1679439 |
|
|
Lo2 |
1482800 |
|
|
LaD |
2000000 |
|
Oceanic |
|
|
|
|
Nx |
2517 |
|
|
Ny |
1793 |
|
|
La1 |
-30419200 |
|
|
Lo1 |
129906005 |
|
|
La2 |
80010000 |
|
|
Lo2 |
10710000 |
|
|
LaD |
2000000 |
|
Code |
Phenomenon/Significance |
Code |
Phenomenon/Significance |
Code |
Phenomenon/Significance |
Code |
Phenomenon/Significance |
|
AF.W |
Ash Fall Warning |
GL.A |
Gale Watch |
<None> |
No Hazard |
WC.W |
Wind Chill Warning |
|
AF.Y |
Ash Fall Advisory |
GL.W |
Gale Warning |
RB.Y |
Small Craft Advisory for Rough Bar |
WC.Y |
Wind Chill Advisory |
|
AS.Y |
Air Stagnation Advisory |
HF.A |
Hurricane Force Wind Watch |
SB.Y |
Snow and Blowing Snow Advisory |
WI.Y |
Wind Advisory |
|
BS.Y |
Blowing Snow Advisory |
HF.W |
Hurricane Force Wind Warning |
SC.Y |
Small Craft Advisory |
WS.A |
Winter Storm Watch |
|
BW.Y |
Brisk Wind Advisory |
HI.A |
Hurricane Wind Watch |
SE.A |
Hazardous Seas Watch |
WS.W |
Winter Storm Warning |
|
BZ.A |
Blizzard Watch |
HI.W |
Hurricane Wind Warning |
SE.W |
Hazardous Seas Warning |
WW.Y |
Winter Weather Advisory |
|
BZ.W |
Blizzard Warning |
HS.W |
Heavy Snow Warning |
SI.Y |
Small Craft Advisory for Winds |
ZF.Y |
Freezing Fog Advisory |
|
CF.A |
Coastal Flood Watch |
HT.Y |
Heat Advisory |
SM.Y |
Dense Smoke Advisory |
ZR.Y |
Freezing Rain Advisory |
|
CF.S |
Coastal Flood Statement |
HU.A |
Hurricane Watch |
SN.Y |
Snow Advisory |
ZY.Y |
Freezing Spray Advisory |
|
CF.W |
Coastal Flood Warning |
HU.S |
Hurricane Statement |
SR.A |
Storm Watch |
|
|
|
CF.Y |
Coastal Flood Advisory |
HU.W |
Hurricane Warning |
SR.W |
Storm Warning |
|
|
|
DS.W |
Dust Storm Warning |
HW.A |
High Wind Watch |
SU.W |
High Surf Warning |
|
|
|
DU.Y |
Blowing Dust Advisory |
HW.W |
High Wind Warning |
SU.Y |
High Surf Advisory |
|
|
|
EC.A |
Extreme Cold Watch |
HZ.A |
Hard Freeze Watch |
SV.A |
Severe Thunderstorm Watch |
|
|
|
EC.W |
Extreme Cold Warning |
HZ.W |
Hard Freeze Warning |
SV.W |
Severe Thunderstorm Warning |
|
|
|
EH.A |
Excessive Heat Watch |
IP.W |
Sleet Warning |
SW.Y |
Small Craft Advisory for Hazardous Seas |
|
|
|
EH.W |
Excessive Heat Warning |
IP.Y |
Sleet Advisory |
TI.A |
Tropical Storm Wind Watch |
|
|
|
EW.W |
Extreme Wind Warning |
IS.W |
Ice Storm Warning |
TI.W |
Tropical Storm Wind Warning |
|
|
|
FA.A |
Areal Flood Watch |
LB.Y |
Lake Effect Snow and Blowing Snow Advis. |
TO.A |
Tornado Watch |
|
|
|
FA.W |
Areal Flood Warning |
LE.A |
Lake Effect Snow Watch |
TO.W |
Tornado Warning |
|
|
|
FA.Y |
Areal Flood Advisory |
LE.W |
Lake Effect Snow Warning |
TR.A |
Tropical Storm Watch |
|
|
|
FF.A |
Flash Flood Watch |
LE.Y |
Lake Effect Snow Advisory |
TR.S |
Tropical Storm Advisory |
|
|
|
FF.W |
Flash Flood Warning |
LO.Y |
Low Water Advisory |
TR.W |
Tropical Storm Warning |
|
|
|
FG.Y |
Dense Fog Advisory |
LS.A |
Lake Shore Flood Watch |
TS.A |
Tsunami Watch |
|
|
|
FL.A |
Flood Watch |
LS.S |
Lake Shore Flood Statement |
TS.W |
Tsunami Warning |
|
|
|
FL.W |
Flood Warning |
LS.W |
Lake Shore Flood Warning |
TS.Y |
Tsunami Advisory |
|
|
|
FL.Y |
Flood Advisory |
LS.Y |
Lake Shore Flood Advisory |
TY.A |
Typhoon Watch |
|
|
|
FR.Y |
Frost Advisory |
LW.Y |
Lake Wind Advisory |
TY.S |
Typhoon Statement |
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FW.A |
Fire Weather Watch |
MA.S |
Marine Weather Statement |
TY.W |
Typhoon Warning |
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FW.W |
Fire Weather Warning |
MA.W |
Marine Weather Warning |
UP.A |
Heavy Freezing Spray Watch |
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FZ.A |
Freeze Watch |
MF.Y |
Dense Fog Advisory |
UP.W |
Heavy Freezing Spray Warning |
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FZ.W |
Freeze Warning |
MH.Y |
AshFall Advisory |
UP.Y |
Heavy Freezing Spray Advisory |
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MS.Y |
Dense Smoke Advisory |
WC.A |
Wind Chill Watch |
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