Aussie METAR / TAF "T" and "Q" lines..?
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Aussie METAR / TAF "T" and "Q" lines..?
Hi guys, I don't get to fly at home in Australia very often as I am based in teh UK, so would appreciate if someone could remind me of the answer (or tell me where to look this up!):
Take the following TAF/METAR data for example:
I recall from when I have previously flown in Australia that the "T" line gives temps in degrees C at various time intervals, and the "Q" is obviously QNH at the same times. But what is time interval? I think I remember it as being 4hrs, but now wonder if it was three?
So for example does the above mean that the forecast QNH will be 1023 at 1800Z, 1025 at 2200Z, 1026 at 0200Z and 1024 at 0600Z, or is it some other permutation?
Likewise, on the METARs there seems to be some auto-generated information that I am not familiar with. I beliebe the "RMK RF" relates to mm of recent / total (24hrs?) rainfall, but have no idea what NDV means, not all the "// //////" etc.
Maybe if someone could just point me to the relevant AIP refs?
Thanks!
Andy
Take the following TAF/METAR data for example:
CAMDEN (YSCN)
TAF YSCN 021611Z 1812 23005KT 9999 SCT050
FM01 15010KT 9999 FEW050
T 14 14 18 21 Q 1023 1025 1026 1024
METAR YSCN 021830Z AUTO 23001KT 9999NDV // ////// 14/09 Q1023
RMK RF00.0/000.0
TAF YSCN 021611Z 1812 23005KT 9999 SCT050
FM01 15010KT 9999 FEW050
T 14 14 18 21 Q 1023 1025 1026 1024
METAR YSCN 021830Z AUTO 23001KT 9999NDV // ////// 14/09 Q1023
RMK RF00.0/000.0
So for example does the above mean that the forecast QNH will be 1023 at 1800Z, 1025 at 2200Z, 1026 at 0200Z and 1024 at 0600Z, or is it some other permutation?
Likewise, on the METARs there seems to be some auto-generated information that I am not familiar with. I beliebe the "RMK RF" relates to mm of recent / total (24hrs?) rainfall, but have no idea what NDV means, not all the "// //////" etc.
Maybe if someone could just point me to the relevant AIP refs?
Thanks!
Andy
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The temps and qnh's are at 3 hour intervals as i recall.
So first one would be at 1800utc then second at 2100 etc.
And pretty the rainfall is rainfall in the last 10 mins / rainfall total since 0900 local time.
So first one would be at 1800utc then second at 2100 etc.
And pretty the rainfall is rainfall in the last 10 mins / rainfall total since 0900 local time.
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The temps and qnh's are at 3 hour intervals as i recall.
So first one would be at 1800utc then second at 2100 etc.
And pretty the rainfall is rainfall in the last 10 mins / rainfall total since 0900 local time.
NDV means No directional variation available.
So first one would be at 1800utc then second at 2100 etc.
And pretty the rainfall is rainfall in the last 10 mins / rainfall total since 0900 local time.
NDV means No directional variation available.
kair1234 is correct.
AIP GEN 3.5 - 30/31 paras 12.15, 12.16, 12.18 and 12.19 here: http://www.airservices.gov.au/public...p48_060831.pdf
UTC + 10 TEMP/QNH:
0400-0700: 14/1023
0700-1000: 14/1025
1000-1300: 18/1026
1300-1600: 21/1024
Nil recorded RF in previous 10 minutes and nil since 0900 local.
VIS in excess of 10k in all directions.
The number of "/"'s are important.
// = WX element of AWS not available
//// = VIS element of AWS not available
////// = cloud element of AWS not available.
In the METAR quoted you didn't get WX or cloud, but you did get VIS (9999NDV)
AIP GEN 3.5 - 30/31 paras 12.15, 12.16, 12.18 and 12.19 here: http://www.airservices.gov.au/public...p48_060831.pdf
UTC + 10 TEMP/QNH:
0400-0700: 14/1023
0700-1000: 14/1025
1000-1300: 18/1026
1300-1600: 21/1024
Nil recorded RF in previous 10 minutes and nil since 0900 local.
VIS in excess of 10k in all directions.
The number of "/"'s are important.
// = WX element of AWS not available
//// = VIS element of AWS not available
////// = cloud element of AWS not available.
In the METAR quoted you didn't get WX or cloud, but you did get VIS (9999NDV)
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9999NDV = VIS in excess of 10k in all directions.
The rainfall is supposed to be stripped from the reports between BOM and us, but often isn't.
This would be pretty important at places which have quite large variations during the day, ie cold at night hot in the middle of the day.
Do you have a reference for using a linear interpolation of temp and QNH, almostthere!?
I can't recall any document suggesting that, or any instructor saying (for example): It's 0531 puffy, so we should change from 1023 to 1024, 'cause that's half way between the 0400 forecast of 1023 and the 0700 forecast of 1025.
You could be right, but it's the first I've heard of it.
I can't recall any document suggesting that, or any instructor saying (for example): It's 0531 puffy, so we should change from 1023 to 1024, 'cause that's half way between the 0400 forecast of 1023 and the 0700 forecast of 1025.
You could be right, but it's the first I've heard of it.
BoM man told us at a seminar that those values are forecast values at that specefic time. Might not be a linear line, but their prediction is the QNH for that time only. QNH could drop 5 mins later as the cyclone decends, but it was an accurate(??) forecast for that particular time.
As the previous poster has said, I have also been at a briefing from BoM guy that said the exact same thing that it is a forecast at a specific time, starting from the beginning of the forecast and then at three hourly intervals thereafter.
Whilst the interpolation would most often make very little difference, it most certainly would if there was big differences between the three hourly forecasts.
In response to what about "It's 0700 puffy, so we should change from using a temperature of 12 to 25 for our TAS calculations." Temperatures and QNH dont just change instantly on the hour so we need to take this into account. Puffy's instructors directions on the QNH seems a lot better than his instructions on temperature!!
Last edited by almostthere!; 4th Oct 2006 at 13:21. Reason: Spelling
That’s all well and good, but what I’m trying to work out is what the required procedure is.
My understanding of the altimetry rules is that they are intended, at least in part, to ensure that everyone in the same area uses the same QNH setting, not necessarily the accurate QNH, taking into consideration things like the QNHs in adjacent areas and know aerodrome QNHs.
Let’s assume we’re both going to fly to Grong Grong with an ETA of 0630, and the TAF for Grong Grong forecasts 1010 for 0400 and 1019 for 0700 – there’s a front forecast to move through.
I’m going to have the altimeter set to 1010, unless one of those nice Flightwatch or ATC people tell me otherwise. Are you saying you’re going to set 1018 or 1019?
Your comment about the numbers being merely point in time forecasts is correct, but that cuts both ways. The forecast could be wrong, and neither of us may be even close to the correct QNH. But don’t you think we should at least have the same setting?
Any IFR boys or girls care to comment on what they would have set at 0630 at top of descent into Grong Grong?
As for temp and TAS calculations, the difference is that in most aircraft you are able to measure and use the actual temperature while you’re flying.
My understanding of the altimetry rules is that they are intended, at least in part, to ensure that everyone in the same area uses the same QNH setting, not necessarily the accurate QNH, taking into consideration things like the QNHs in adjacent areas and know aerodrome QNHs.
Let’s assume we’re both going to fly to Grong Grong with an ETA of 0630, and the TAF for Grong Grong forecasts 1010 for 0400 and 1019 for 0700 – there’s a front forecast to move through.
I’m going to have the altimeter set to 1010, unless one of those nice Flightwatch or ATC people tell me otherwise. Are you saying you’re going to set 1018 or 1019?
Your comment about the numbers being merely point in time forecasts is correct, but that cuts both ways. The forecast could be wrong, and neither of us may be even close to the correct QNH. But don’t you think we should at least have the same setting?
Any IFR boys or girls care to comment on what they would have set at 0630 at top of descent into Grong Grong?
As for temp and TAS calculations, the difference is that in most aircraft you are able to measure and use the actual temperature while you’re flying.
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Grong Grong forecasts 1010 for 0400 and 1019 for 0700 – there’s a front forecast to move through.
Are you saying you’re going to set 1018 or 1019?
And even if it were 9mb, in must situations ~300' won't spoil your day in VMC (unless very low over the terrain in the first place!?). It may be of more concern if doing a non-precision (e.g. NDB) IAP of course... in which case I would want to have some means of getting the info from FIS or elsewhere... but still I think the idea of a 9mb change is pretty unlikely!?
Anyway, I am happy with the 3hr intervals info above - thanks!!
Andy
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