Forecast Content

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

  • 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 (%)

  • Hgt – Geopotential height (meters AMSL)

Level FL U Wind V Wind Temp RH Hgt

850

050

X

X

X

X

X

750

080

X

X

X

X

X

700

100

X

X

X

X

X

600

140

X

X

X

X

X

500

180

X

X

X

X

X

450

210

X

X

X

X

X

400

240

X

X

X

X

350

270

X

X

X

X

300

300

X

X

X

X

270

320

X

X

X

X

250

340

X

X

X

X

225

360

X

X

X

X

200

390

X

X

X

X

175

410

X

X

X

X

150

450

X

X

X

X

125

480

X

X

X

X

100

530

X

X

X

X

Max Wind

X

X

X

Trop

X

X

Grid Resolution

1.25 degree Latitude/Longitude grid

Forecast Interval

3 hours

Forecast Length

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

File Counts

1 file for each parameter
79 files for each forecast interval
11 forecast intervals
Total 869 files for each forecast update

Update Period

Every 6 hours

File Packaging and Bundling

The flight planning data is packaged as individual GRIB 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.

File Bundle Naming Convention

The individual GRIB 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:  KWBC_WAFS<MM><DD><HH>_<FF>.TGZ
Where:

MM= Model Run Month Code
DD= Model Run Date Code
HH= Model Run Hour
FF= Forecast Code

Model Run-time Code:

00z       ( Filename Code= 00 )
06z       ( Filename Code= 06 )
12z       ( Filename Code= 12 )
18z       ( Filename Code= 18 )

There is one TGZ file for each each forecast hour.

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.

File Naming Convention

The flight planning files use a WMO Header file naming convention:

Filename definition:  <M><P><G><I><LL>
Where:

M= Model Code (always H)
P = Parameter Code
G = Grid Code (always X)
I = Forecast Interval Code
LL = Level Code

Parameter Code (P) Forecast Interval Code (I) Level Code (LL)
Code Description Code Description Code Description

H

Height (Geopotential)

C

6 hour forecast

10

100hPa

R

Relative Humidity

D

9 hour forecast

13

125hPa

T

Temperature

E

12 hour forecast

15

150hPa

U

U (North) Wind Component

F

15 hour forecast

18

175hPa

V

V (West) Wind Component

G

18 hour forecast

20

200hPa

H

21 hour forecast

23

230hPa

I

24 hour forecast

25

250hPa

J

27 hour forecast

27

270hPa

K

30 hour forecast

30

300hPa

L

33 hour forecast

35

350hPa

M

36 hour forecast

40

400hPa

45

450hPa

50

500hPa

60

600hPa

70

700hPa

75

750hPa

85

850hPa

96

Level of the Maximum Wind

97

Level of the Tropopause

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.

File structure

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

Category: FAQ's