||CC/CCCC = The international four-letter location indicator (in upper-case) of the responsible RTH (eg EDZW, RJTD, EGRR etc..Full details as regards abbreviated headings are contained in WMO Publication No. 386 - Manual on the GTS - Vol I - Part II.
||nn = Sequence number of the advanced notification file. There are two different series of the sequence number (01 to 99) one for "observational data" and one for "products" (i.e. “F”= O and “F”= P) which are initialized at the beginning of each year.
|| m = The month of updating the file:
1=January 6=June A=October
2=February 7=July B=November
3=March 8=August C=December
||dd= The day of updating the file:
01= 1st of the month, 02= 2nd of the month etc... Sequence number of the advanced notification file. There are two different series for the sequence numbers (01-99) one for "observational data" and one for "products" (i.e. “F”= O and “F”= P). These are initialized at the beginning of the year.
||F = File identification: to distinguish the type of the contents:
O = observational data file / P = product file
- Observational data file = O for Observations:
where T1= any other letter than those used for Products
- Product file =P for Products: where T1=D, G, H, J, P, Q, X,Y
||.txt = Is a constant character-set (small letters) which indicates a file in ASCII format.
In case of a server which has no distinction between capital and small letters in file system, either of them is used for the file name.