QNH in a TAF
I haven a question re QNH from a TAF. The AIP states the TAF values relates to 3 hr blocks from the start of the forecast period i.e HH HH+3 HH+6 HH+9
Now i have seen some references that note these values are actually only valid across 90 min blocks e.g
If we have a forecast from 0200 the TAF QNH values reading 1010 1011 1012 1013
Do I read that as as
Time
0200 - 0330 is 1010
0330 - 0630 is 1011
0630 - 0930 is 1012
0930 - 1230 is 1013
Or
0200 - 0500 is 1010
0500 - 0800 is 1011
0800 - 1100 is 1012
1100+ is 1013
?