This is a newly developed recommended practice for the exchange of information between
Centers over the GTS when they are using FTP to PUSH files to the next center. The
recommendation will be published in the November 3, 2003 update to the WMO Manual 386
Attachment 15. The Washington RTH will use this practice for delivery of files containing
WMO bulletins. See file ingest documentation for a discussion
on accumulating bulletins in files and the structure of the file content using product separators. The file content "flag
field" for forming the content of a file of bulletins is applied in the building of
all AHL product files in the Gateway.
The following information was extracted from the Cairns, Australia WMO WWW
CBS - Ext (02) [4 to 12 December 2002] meeting documents that were recommended for
as ammendments to Manual 386 Attachment II-15.
FILE NAME STRUCTURE
The file naming convention
The following file naming convention should be implemented with a transition period not exceeding 2007.
The file name format is a predetermined combination of fields, delimited by the _ (underscore) character
except for the last 2 fields, which are delimited by the . (period) character. each field can be of variable
length, except for the Date/Time stamp field which is predetermined.
The order of the fields is mandatory and the file name fields are as follows:
where the mandatory fields are:
pflag = is a character or combination of characters indicating how to decode the product identifier field. At this time, the pflag field has only
the following acceptable values:
Table 4.1 Accepted pflag values
|| The product identifier field will be decoded as a standard
T1T2A1A2ii data designator (The WMO standard data designators
are given in Attachment II-5)
|| The product identifier field will be decoded as a standard
Abbreviated Heading, including BBB as appropriate, space
characters being discarded. e.g. T1T2A1A2iiCCCCYYGGgg[BBB]
|| Planned WMO Product Identifier
|| Originating centre's local product identifier
productidentifier = is a variable length field containing information that describes the nature of the data in the field. The productidentifier field should be decoded according to the pflag.
oflag = is a character or combination of characters indicating how to decode the originator field. At this time, the oflag field has only the following acceptable value:
Table 4.2 Accepted oflag values
|| The originator field will be decoded as a standard CCCC site id
originator = is a varible length field containing information that states where the file originated from. The orginator field should be decoded
according to the oflag.
yyyyMMddhhmmss = is a fixed length date and time stamp field. The
interpretation of this field should be in accordance with the standard rules set for specific data description and types. Therefore,
it may have various significance such as date of creation of the file, or date of collection of data. If a particular
date and time stamp field is not specified, it should be replaced by a '-' (minus) character
For example: ----311500-- represents a stamp that specifies only the day (31), hours (15) and minutes (00). If there
are no rules for a specific data type, this field should represent the date and time of creation of the file by the originator.
type = is a varible length field that describes the general format type of the fiel. Although
this information could be considered somewhat redundant to the productidentifier field, it is kept as such for
industry accepted standard compatibility. It should be noted that the delimiter
before the type field is a . (period). This is to help parse the file name for fields, since the freeformat field could make use of further __ (underscore) to delimit subfields.
Table 4.3 Accepted type values
|| The file is a metadata file pair which describes the content and
format of the corresponding information file with the same name.
|| TIFF file
|| GIF file
|| PNG file
|| Postscript file
|| MPEG file
|| JPEG file
|| text file
|| HTML file
|| a file containing data encoded in a WMO binary code form such as
GRIB or BUFR
|| a Microsoft Word file
|| A corel WordPerfect file
And the non mandatory fields are:
freeformat = is a varible length field containing further descriptors as required by a given originator. This field can be
further divided in sub-fields. Originating countries should strive to make their freeformat descriptions available to others.
compression = is a field that specifies if the file using industry standard compression techniques.
Table 4.4 Accepted compression values
|| The file has been compressed using the Unix COMPRESS technique
|| The file has been compressed using the PKWare zip technique
|| The file has been compressed using the Unix gzip technique
|| The file has been compressed using the Unix bzip2 technique
Maximum file name length:
Although no maximum length is specified for the entire file name, the mandatory fields shall not exceed 63 characters
(including all delimiters) to allow processing by all international systems.
The filenames shall be compossed of any combination of the standard character set (ITU-T Rec.X.4) with the
exceptions noted in Table 4.5.
Table 4.5 Symbols for filenames
|| The underscore symbol is used as a delimiter symbol. To be
used only as a delimiter of fields. The underscore is also
accepted in the freeformat field, but not in other fields.
|| The period symbol is used as a delimiter symbol. To be used
only before the type and compression fields.
|| Forward stroke often has special meaning for the full path
specification for a filename in some operating systems
|| Backward stroke often has special meaning for the full path
specification of a filename in some operating systems
|| Greater than symbol shall not be used since of often represents
special file manipulation in some operating systems
|| Less than symbol shall not be used since it often represents
special file manipulation in some operating system
|| Vertical bar (pipe) symbol shall not be used since it often
represents special file manipulation in some operating systems
|| Question mark symbol shall not be used
|| Single quote shall not be used
|| Double quote shall not be used
|| The star symbol is often used for wildcard specification in
procedures that process filenames
|| The space symbol shall not be used
|| The comma symbol can be used in the freeformat field
| A-Z a-z
|| alphanumeric symbols may be used in all fields
The structure of the '.met' file, related to the WMO Metadata standard, is not defined in this guide.
File Name Examples
A possible imagery file (sig weather chart) that would have originated from the USA:
A possible model output file from France:
A possible image from Australia:
Note that: this shows that the date and time stamp is to be interpreted to be 00 hours, 00 minutes and 00 seconds.
A possible compressed TOVS sat4llite data file from the United Kingdom:
A possible image (radar) from Canada:
A possible single-record GRIB file from Canada:
A possible multiple record batch file from China: