QNH in a TAF
Excellent! Exactly what I've said in my last two posts!
Now, the very next paragraph says to use linear interpolation for values in between the time points...
But does not say to round them down.
Common practice is to round down when utilising interpolated QNH but it is a safe action, not a mandated one. When IFR, if you're using Area QNH or forecast QNH, you straightaway increase minimums by at least 100', but the minima themselves aren't affected.
Again, CASA will not have an exam with;
as you seem to be concerned so much about.
KISS priniple!
I suppose if you ask long enough someone will agree with you.
Have whinge about being picked on, but jeez dude, you're gonna have to harden the fcuk up when someone directs a mildly sarcastic remark your way. You've gone a bit Charlie Sheen here. My first post actually leaned toward your interpretation, but don't lash out at anyone who doesn't agree 100% with you.
Now, the very next paragraph says to use linear interpolation for values in between the time points...
But does not say to round them down.
Common practice is to round down when utilising interpolated QNH but it is a safe action, not a mandated one. When IFR, if you're using Area QNH or forecast QNH, you straightaway increase minimums by at least 100', but the minima themselves aren't affected.
Again, CASA will not have an exam with;
At 4:30, what will the pressure atitude at Sea Level be?
A) 90'. (for 1010 HPa)
B) 65.1'. (for 1010.83 HPa)
C) 60. (for 1011 HPa)'
A) 90'. (for 1010 HPa)
B) 65.1'. (for 1010.83 HPa)
C) 60. (for 1011 HPa)'
KISS priniple!
I suppose if you ask long enough someone will agree with you.
Have whinge about being picked on, but jeez dude, you're gonna have to harden the fcuk up when someone directs a mildly sarcastic remark your way. You've gone a bit Charlie Sheen here. My first post actually leaned toward your interpretation, but don't lash out at anyone who doesn't agree 100% with you.
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It says observed values, ie. If their mickey doo baro says 1013.5, they will publish 1013.
I don't mind being pointed out as wrong but I object to people using incorrect or unsubstantiated information to make out that I am incorrect or that they are above me.
My part in this thread has gone on long enough and would appear to have served no purpose so c'est la vie.
My part in this thread has gone on long enough and would appear to have served no purpose so c'est la vie.
As a once certified Met observer (maybe still am - does it ever lapse?) and once Briefing Officer (definately lapsed!) my take is that you should read and apply the section in AIP regarding QNH as a whole. It is included as an explanation as to the decode of QNH in regard to observations (METAR/SPECI) and forecasts (TAF/TTF etc), there is no distinction between the two. The BoM quite clearly always rounds down (and they provide the raw info), AIP Met section reflects their practices. If an interpolation between 2 forecast QNH's gives an intermediate result, then using the rule applied to an actual observation (i.e. a forecast observation) if done at that time with that same result, it would be rounded down. My interpretation of "Observed" in this sense would be any intermediate value that is arrived at by whatever means.
