The GRIB2 0.5 degree data set is sourced from the US NOAA/NWS GFS model.

NOTE: DTN no longer supports the Legacy Flight Hazards, those products have been removed from these packages.

Forecast Content

Below is a summarization of the flight planning data content provided for each forecast period and for each grid, where:

Abbreviation Description Units

Level

Pressure Level

hPa

FL

Flight Level

100’s of feet AMSL unless otherwise noted

U Wind

North Component of wind

m/sec

V Wind

West Component of wind

m/sec

Temp

Air Temperature

degrees K

RH

Relative Humidity

%

Press

Air pressure

hPa

Hgt

Geopotential Height

m (AMSL)

 

Level FL U Wind V Wind Temp RH Press Hgt

MSL

0

X

Sfc

0

X

X

X

X

X

1000

001

X

X

X

X

X

980

010

X

X

X

900

030

X

X

X

850

050

X

X

X

X

X

750

080

X

X

X

700

100

X

X

X

X

X

650

120

X

X

X

600

140

X

X

X

X

X

550

160

X

X

X

500

180

X

X

X

X

X

475

200

X

X

X

425

220

X

X

X

400

240

X

X

X

X

375

260

X

X

X

350

270

X

X

X

X

325

280

X

X

X

300

300

X

X

X

X

275

320

X

X

X

260

330

X

X

X

250

340

X

X

X

X

230

350

X

X

X

225

360

X

X

X

215

370

X

X

X

210

380

X

X

X

200

390

X

X

X

X

190

400

X

X

X

180

410

X

X

X

160

430

X

X

X

150

450

X

X

X

X

100

530

X

X

X

X

50

630

X

X

X

X

30

710

X

X

X

X

Max Wind

X

X

X

Trop

X

X

Grid Resolution

Half degree (0.5º) global

Forecast Interval

3 hours 

Forecast Length

36 hours (3, 6, 9, 12, 15, 18, 21, 24, 27, 30, 33, 36 hour forecasts) 

File Counts

1 file for each Level
126 files for each forecast interval
12 forecast intervals

Total 1512 files for each forecast update 

Update Period

Every 6 hours 

File Packaging and Bundling

The flight planning data is packaged as individual GRIB2 files named with the WMO Header that each has. Therefore, each file contains one parameter for one particular forecast period and atmospheric level. These files are then bundled into TGZ files for distribution.

The GRIB2 compression is defined in the header information included in the data files. For further information review Section 4 Binary Data Section (BDS) found in the link below.
http://www.wmo.int/pages/prog/www/WDM/Guides/Guide-binary-2.html

TGZ File Bundle Naming Convention

The individual GRIB2 files are tar’ed together and then compressed by standard zip utility application for distribution. The naming convention of the tar’ed, zip file is:
Filename definition:  <CCCC><MMM>2_RR<DDHH>_<FF>.TGZ
Where:

CCCC = Issuing office identifier (KWBC)
MMM = Model (GFS)
RR = Resolution
DD = Model Run Date
HH = Model Run Hour (00, 06, 12, 18)
FF = Forecast hour (06, 09, 12,…36)

There is one TGZ file for each each forecast hour.

Individual GRIB File Naming Convention

Each TGZ file contains multiple files for each individual GRIB2 parameter and level.

File Names and Packaging

The flight planning data is packaged in individual files, with one file for each GRIB bulletin. This means that the same filenames are reused with every 6 hourly update.
The GRIB2 compression is defined in the header information included in the data files. For further information review Section 4 Binary Data Section (BDS) found in the link below.
http://www.wmo.int/pages/prog/www/WDM/Guides/Guide-binary-2.html

File Naming Convention

The flight planning files use a WMO Header file naming convention (These are identical to the currently operational UKMO GRIB2 data set). Highlighted items are changes from UKMO GRIB2 data)
Filename definition:  <M><P><G><I><LL>
Where:

M= Model Code
P = Parameter Code
G= Grid Code
I = Forecast Interval Code
LL = Level Code

Model Code Parameter Code Grid Code Forecast Interval Code Level Code
H (Always) Code Description Code Description Code Description Code Description

H

Height (Geopotential)

Y

NCEP GFS 1/2º global grid

B

3 hour forecast

03

30 hPa

P

Pressure

C

6 hour forecast

05

50 hPa

R

Relative Humidity

D

9 hour forecast

10

100 hPa

T

Temperature

E

12 hour forecast

15

150 hPa

U

U (North) wind component

F

15 hour forecast

16

160 hPa

V

V (West) wind component

G

18 hour forecast

18

180 hPa

H

21 hour forecast

19

190 hPa

I

24 hour forecast

20

200 hPa

J

27 hour forecast

21

210 hPa

K

30 hour forecast

D1

215 hPa

L

33 hour forecast

22

225 hPa

M

36 hour forecast

23

230 hPa

25

250 hPa

26

260 hPa

27

275 hPa

30

300 hPa

32

325 hPa

35

350 hPa

37

375 hPa

40

400 hPa

42

425 hPa

47

475 hPa

50

500 hPa

55

550 hPa

60

600 hPa

65

650 hPa

70

700 hPa

75

750 hPa

85

850 hPa

90

900 hPa

D0

980 hPa

89

Mean Sea Level

96

Level of the Maximum Wind

97

Level of the Tropopause

98

Surface of the Earth

99

1000 hPa

Each file is a single GRIB bulletin, with a marker at the head and at the end. The head marker is the ASCII text “GRIB”; the tail marker is a sequence of four ASCII 7’s, as in “7777”. See below.

[start of file]
…..
“GRIB” … [GRIB content] … “7777”
…
“GRIB” … [GRIB content] … “7777”
…
[end of file]

Category: FAQ's