TAF translation for a newbie....

[bookworm]

'Ceiling' is used in USA/Canada meaning lowest layer of 5 oktas or more.

As it does in the rest of the world. However the height at which cloud is no longer reported appears to vary with local procedures. With UK Civil Airport procedures, EGSS could have had an overcast layer of cloud at 5100 ft which would go unmentioned in the METAR. And by my own observation, there was a broken layer considerably below 12,000 ft yesterday evening. UK Military procedures appear to permit the reporting of cloud to much higher levels (BKN300 in one METAR I've seen). Other states seem to have other conventions. I think the 12,000 ft comes from the following in the (US) FMH

9.4.1 Sky Condition Observing Standards. Sky condition shall be evaluated at all stations with this capability. Automated stations shall have the capability to evaluate sky condition from the surface to at least 12,000 feet. Observers at manual stations shall evaluate all clouds and obscurations visible; the 12,000 foot restriction shall not apply.

The point is that the correct interpretation is about more than simply translating coded abbreviations into words (just as with TEMPO in a TAF). Generally, I think the ADDS translator has made a good attempt -- though the bug BackPacker noticed in TAF interpretation is quite a serious one.

[BackPacker]

though the bug BackPacker noticed in TAF interpretation is quite a serious one.

Flattered...

Anyway, if somebody wants to use my posts and send it in as a bug report to ADDS, by all means go ahead. I'm going on vacation tomorrow and won't have time to do it myself. But I do have the feeling that it might just be worth sending it in.

SoCal App? Bookworm?

[BackPacker]

I've looked but have not been able to find any real examples of PROBnn TEMPO in US TAFS.

Bookworm neither. See post #20.

So when all said and done - the UK TAF does not appear to confirm to the NOAA spec.

But that's not the point, is it? The ADDS site gives access to international TAFs and claims to interpret them. The least they could do is write their interpretation algorithm to the ICAO standard, so that all proper ICAO TAFs are properly interpreted. If the NOAA spec is tighter, fine, it will work anyway. If the NOAA spec adds things to a TAF or METAR (I seem to remember a RMK section with AO2 things in it in US METARS), add them to the algorithm to have them interpreted correctly as well.

Or add a disclaimer saying that non-US TAFs will not be correctly interpreted, with a link to an explanation as to why not.

But frankly, right now it simply doesn't work. My first try today (EHRD TAF) shows the exact same bug as we discussed a few days earlier.

EHRD 120554Z 120716 27010KT 9999 FEW015 SCT030 BECMG 0709 26015KT PROB30 TEMPO 0716 7000 -SHRA SCT020CB BKN030

[bookworm]

I do not think this is a bug in the NOAA translation of the TAF.

quote from the NOAA website:
The TAF code, as described here, is the one used in the United States.

I'm not set on criticising the ADDS decoder -- it's probably fit for the purpose it's intended for. I'm just pointing out some of the issues with automated decoding.

TAF is a World Meteorological Organisation standard, BTW. "PROBnn TEMPO" is part of that standard. It's unsurprising that some states, particularly the US, do things slightly differently to accommodate local habits and practices.

[bern444]

SO the solution is to use your own UK/Euro based METAR/TAF translation service.

Small problem - the UKMO doesn't have one of those. This is where I came in, as we used to say when I were a lad......

B

[bern444]

So, to sum up, if I may....

Representatives of the UKMO repeatedly tell me that it isn't possible to decode TAFs online, because they are international, and not everyone speaks English.

NOAA do exactly what the UKMO say is impossible, but although the code is "international", there turn out to be variations, even between two of the most prominent nations involved in weather forecasting.

The email address to write to is - [email protected]

Bernard Newnham

[bookworm]

bookworm - out of interest do you have a link to the ICAO TAF standard?

I'm afraid it's part of the WMO Manual on Codes (Document No. 306) which is not freely published online. I have only hard-copy. I'll gladly look up anything specific for you, but I guess you were just interested to browse it.

[bern444]

It seems things are changing. This from the Met Office (of course, being them, you have to log in, though it is free) -

"We are working on providing decoded TAFs for the GA community as part of the GA briefing service - and will be present in the next release of the service. You will be pleased to know that now have a working decode.

The timescales for release are yet to be defined, as the service currently sits on one of our web servers which we are working on retiring and the new servers are currently being load tested for use. Realistically, I think this will be either late this year or early in 2009 as we are reticent to change the service during the summer when it has higher usage.

A full decode for UK Tafs and Metars can be found on our website under the help and information tab of the Briefing Service -
Taf Decode: http://secure.metoffice.com/aviation/taf_decode.jsp
Metar decode; http://secure.metoffice.com/aviation/metar_decode.jsp

These will be updated in line with the Amendment 74 changes in November.

I hope that this helps with your discussions, but please do not hesitate to get back to me at any time if you need any more clarification.

Kind regards

Hilary

Hilary Clements Marketing Manager
Met Office FitzRoy Road Exeter Devon EX1 3PB United Kingdom"

[liam548]

having done the MET exam I am practicing reading TAFs and METARs.

EGNM is currently EGNM 040720Z 14015KT 0800 R14/P1500 SN VV/// M00/M00 Q0974 14594099

I dont recall studying anything that explained all the numbers at the end of this METAR. Decoder translates it but still...


Location: EGNM
Day of month: 04
Time: 07:20 UTC
Wind: True direction = 140 degrees, Speed: 15 knots
Visibility: 800 m
Runway 14, touchdown zone visual range is variable from a minimum of more than 1500 meters until a maximum of meters
Weather: Snow
Sky is obscured -- vertical visibility cannot be assessed
Temperature: -00 degrees Celsius
Dewpoint: -00 degrees Celsius
QNH (Sea-level pressure): 974 hPa
Runway state:
Runway 14 (or 14 Left): wet snow, contamination 51% to 100%, deposit is 40 mm deep, braking action figures are unreliable

[bookworm]

UK GEN 3.5.10 para 12

[liam548]

Originally Posted by bookworm

UK GEN 3.5.10 para 12

thank you that clears it up.

Didnt come across that during my reading.

[BackPacker]

In the "information age"... with iPhones.. and all this wonderful technology... we are still using this holdover from the ticker-tape days.

At least that ticker tape technology didn't break down as unexplained as PPRuNe has over the last few days.

Anyways, in the digital age, would the METAR really be that much clearer to read?

<METAR>
<LOCATION FORMAT=ICAO>EGNM</LOCATION>
<DATE FORMAT=YYYYMMDD>20081204</DATE>
<TIME TZ=UTC FORMAT=HHMM>0720</TIME>
<VISIBILITY UNIT=M>0800</VISIBILITY>
<VISIBILITY UNIT=M RUNWAY=14>1500</VISIBILITY>
<VISIBILITY_TREND RUNWAY=14>P</VISIBILITY>
<PRECIPITATION>SN</PRECIPITATION>
<VERTICAL_VISIBILITY>NO VALUE</VERTICAL_VISIBILITY>
<TEMPERATURE UNIT=C>-0</TEMPERATURE>
<DEWPOINT UNIT=C>-0</DEWPOINT>
<QNH UNIT=HPA>0974</QNH>
<DATA>EGNM 040720Z 14015KT 0800 R14/P1500 SN VV/// M00/M00 Q0974</DATA>
</METAR>