TAF translation for a newbie....

[liam548]

:confused:

for Leeds Bradford (EGNM) today

LEEDS BRADFORD


EGNM 061516Z 061601 15010KT 9999 SCT020 TEMPO 1620 7000 SHRA BKN010TCU PROB30 TEMPO 1620 4000 +SHRA +TSRA BKN008CB BECMG 1720 24006KT BECMG 2023 7000 BKN008 TEMPO 2301 3000 BR BKN003



Can someone explain it please. It has been explained once before to me but not in writing so I can refer back to it and get used to reading them. I understand bits but not other parts.

Thanks in advance

Liam.

[Johnm]

If you register free at Met Office: Weather and climate change (http://www.metoffice.gov.uk) then log on and go to Met Office: Online services - customer login (http://secure.metoffice.com/aviation/taf_decode.jsp) you will find the answer

[Johnm]

Well done G-EMMA that looks pretty good to me!

[PompeyPaul]

Egnm 061516z 061601 Crap Wx

[Pitts2112]

In short, it means you ain't goin' anywhere! :(

Greatest TAF decode I've heard so far:

If the TAF is:

1 line - you can pretty well go
2 lines - Only people with IMC ratings are going anywhere
3 lines - no one's goin' anywhere

As crude as it sounds, it's not often that far off! :)

[spittingimage]

... and times are given in UTC.

[BackPacker]

Well done G-EMMA. Just one minor addition. Every "BECMG" and "TEMPO" group supersedes the previous, and in most cases the PROB groups will be aligned with the timing of the BECMG and TEMPO groups so they also supersede the previous.

So if you want to break it down into multiple paragraphs, here's how to do that:

EGNM 061516Z 061601 15010KT 9999 SCT020 <- The general overall picture at the start of the period, so at 16Z. Anything in here that's not superseded later on will remain valid throughout the period.

TEMPO 1620 7000 SHRA BKN010TCU <- Temporary condition between 16Z and 20Z, after which, if nothing else mentioned, it reverts back to 15010KT 9999 SCT020

PROB30 TEMPO 1620 4000 +SHRA +TSRA BKN008CB <- But within this same period it might get worse.

BECMG 1720 24006KT <- Ah, between 17Z and 20Z the wind will become 240/6. But for the rest the previous still applies. So theoretically, if the forecast holds true, at 20Z the conditions are 24006KT 9999 SCT020

BECMG 2023 7000 BKN008 <- And this is what's going to get established from 20Z to 23Z. So at 23Z the conditions should be 24006KT 7000 BKN008.

TEMPO 2301 3000 BR BKN003 <- And from 23Z onwards it will worsen once again.

Oh, and all times are UTC, not local.

[BackPacker]

Pretty cool

I just find it confusing. They put the original TAF text in, suggesting that what comes next is an interpretation of that bit of text. But what they actually do is take the whole TAF into account. That's why you see things like:

Text: EGNM 061810Z 061904 24006KT 9999 SCT020
Forecast period: 1900 to 2000 UTC 06 July 2008

Where does the 2000 UTC comes from? This bit applies to 0400 UTC, doesn't it? Oh no, later on, you'll find

BECMG 2023 7000 BKN008

So that's where the 2000 UTC comes from.

So... Pretty smart analysis algorithm, lousy presentation of the results.

This is the site I like better:

MET'MAP - ORBIFLY FLIGHT SCHOOL - IFR ET CPL AMERICAIN EN EUROPE - FAA IFR AND CPL IN EUROPE (http://www.orbifly.com/ORBITEST/metmap.php?region_choose=GEN&mode=metar&icao_choose=EHAM&lang=ENG)

Mouse over a site to see the METAR and its interpretation. Click on a site to make it your personal center of the universe, then bookmark whatever URL is listed for next time. They don't interpret TAFs though, only METARS. But they do give access to both the short and long term TAFs and I also like the color coding to get a glance of flight conditions. Especially if you combine that with rainfall radar or something like that.

[Papa Charlie]

I was taught that the longer the TAF, the worse it is to fly...! ;)

[frontlefthamster]

Well, I just got proper training so that I could read and understand them the same way I read and understand a book. Oh, and proper training in meteorology, climatology, forecasting, modelling, and so forth too.

How little I knew, eh?

[Irv]

If the TAF is:

1 line - you can pretty well go
2 lines - Only people with IMC ratings are going anywhere
3 lines - no one's goin' anywhere

You'll be seeing 4 lines soon... they are going to 36 hour tafs at some places later this year - all the 'times' will extend to be 'day/time', and you can be sure they'll cover every possible option with 'prob30 this and that' within the 36 hours. The decode sites will have to change, wonder how fast that will happen?

[BackPacker]

Been looking at that ADDS thing a bit more. There's something seriously wrong with that algorithm. The interpretation is done correctly, as is the presentation. But then the wrong bits of TAF are associated with the presentation bits. Everything is well (excellent, actually) up to the PROB30 bit.

Then comes the following line:
Text: PROB30
And some text suggesting it interprets that line. But what that piece of text actually interprets is
Text: PROB30 TEMPO 1920 4000 +SHRA +TSRA BKN008CB
which is correct, as this is one "block".

The next "block" then seems to interpret the line
Text: BECMG 2023 7000 BKN008
But this line is listed after the block it interprets. Because the line preceding it is the "TEMPO 1920 ..." line which should have been on the PROB30 line.

So past the PROB30 bit, all the content of the "Text:" lines need to be shifted up one block to make things fit. And even then the interpretation block doesn't neatly interprets what's on the "Text:" line, since the interpretation also looks through the rest of the TAF for anything that precedes or supersedes this bit of "Text:" line.

Just guessing what happened: A smart programmer wrote an algorithm to make a linear interpretation of a TAF, from hour to hour, and present it in text form. Which worked flawlessly. And this is no mean feat, because to interpret what the weather is going to be at the end of the period may mean going backwards in the TAF a few "blocks", and to interpret how long the initial weather is going to last may mean going forward in the TAF.

Then a customer request comes along to have the actual TAF text inbetween the interpretation. Which isn't possible in this case since a TAF isn't necessary linear, but the algorithm linearizes the results. So the smart programmer refuses, tries to explain this to his non-understanding management or non-understanding customers, and moves on.

Anyway, request persists, so a less intelligent programmer comes along, willing to take the job (after all, a TAF is in ALL CAPS so it can't be difficult), finds he doesn't understand the code programmer #1 has written so he writes his own algoritm that breaks the TAF into blocks. And then injects these blocks into the blocks that the original algorithm spews out. A quick test by management finds no flaws with this so the thing goes into production.

And the worst thing is that that second programmer probably made a lot of money. First for taking on a job that everybody said was impossible, and secondly for getting it through acceptance testing. In less time than expected.

(Is it true you turn into a cynic after working in the same field for 10 years?:*)

[DX Wombat]

30% chance that temporarily between 4 in the afternoon and 8 in the evening it will deteriate to visibility of 4000m in heavy showers of rains and heavy thunderstorms and rain, cloud lowering to broken at 800ft cumulonimbus 30%? Make that 100% :( I was with friends at Hebden all day and at 17:00hrs we had all of that - TS, heavy rain, low cloud etc. Driving home with the temperature at 11.5C we had radiation fog forming :uhoh: it looked quite pretty floating gently about 6" above the fields and between the trees. It also poured down whilst we spent a couple of hours at Brimham Rocks.
For anyone who may not be too familiar with the geography of the UK, Hebden and Brimham Rocks are places in the Yorkshire Dales National Park. :)

[XL319]

wx is always crap at LBA :}

[Duchess_Driver]

most accurate forecast I've heard recently...

The Weather is PANTs........Poor Actuals and Naff TAFs

[bookworm]

Been looking at that ADDS thing a bit more. There's something seriously wrong with that algorithm. The interpretation is done correctly, as is the presentation. But then the wrong bits of TAF are associated with the presentation bits. Everything is well (excellent, actually) up to the PROB30 bit.

Well spotted. I think the key issue is that "PROB30 TEMPO" is fairly rare in US TAFs. If you speak SQL, here's the difference between the US and UK interpretations of the WMO's "TAFs for Dummies".


avbrief=# select count(*) from taf where icao ~~ 'K%' and text ~ 'PROB30';
count
-------
349
(1 row)

avbrief=# select count(*) from taf where icao ~~ 'K%' and text ~ 'PROB30 TEMPO';
count
-------
0
(1 row)

avbrief=# select count(*) from taf where icao ~~ 'EG%' and text ~ 'PROB30';
count
-------
205
(1 row)

avbrief=# select count(*) from taf where icao ~~ 'EG%' and text ~ 'PROB30 TEMPO';
count
-------
200
(1 row)



Looking at some of the examples, TEMPO seems to be implied by PROB30 in some cases.

Thus my guess is that the algorithm was not tested on cases where two change words like "PROB30 TEMPO" appear consecutively.

[BackPacker]

Come to think of it, I like the US system better. I mean PROB30 would imply a TEMPO condition, wouldn't it? In what sort of situations would you have a PROB30 BECMG?

[bookworm]

Come to think of it, I like the US system better. I mean PROB30 would imply a TEMPO condition, wouldn't it?

No. There's a big difference between "3000 BKN006 PROB30 0710 0200 FG OVC000" and "3000 BKN006 PROB30 TEMPO 0710 0200 FG OVC000".

In the first case, the airport might well be fogged out for the entire period. In the second case, there should be an opportunity to make an approach at some stage. Don't bet your life on it though.

[liam548]

Thanks for all the replies and discussion.

Great thing t'nternet aint it :)

[avonflyer]

dont you just hate PROB50 +SHRA

it might rain it might not ..... I can do that type of forecast for free...

[bern444]

There's a big difference between "3000 BKN006 PROB30 0710 0200 FG OVC000" and "3000 BKN006 PROB30 TEMPO 0710 0200 FG OVC000".

It took me a while to work through section by section to work out the difference, and I have the feeling I might not be the only one. A question we (a group from our club) always ask at exhibitions is - why not print it in English too? We know there are international standards and all that, and certainly if it has FG in it I won't be leaving home, but nevertheless the potential for getting it wrong when you can easily transpose two groups in a complex code seems very high.

We've put the question at several AeroExpos and other exhibitions now, and not had a good answer. I know there are decoder sites around the place, but they aren't the official word, and it seems to us it would be easly to have a computer decode alongside the TAF or METAR. NOAA seems to manage it automatically on their ftp site, so why can't we?

Bernie

[PompeyPaul]

why not print it in English too?Because that would start to make flying accessable to all, and after spending £10k on a license I want to be special and able to decode those archaic runes.

Could you imagine if johnny public knew how to respond if fired at with a green flare, given a flare gun and a red and green charge in the cockpit ? There would be a bloody stampede.

[bookworm]

A question we (a group from our club) always ask at exhibitions is - why not print it in English too?

I think this case is actually a good example of why printing it in English is not the answer. It would be trivial to transcribe the symbol TEMPO into the word "temporarily". However the subtlety and difficulty is in the interpretation of the word, however written, which means "for periods not exceeding 1 hour duration in each instance, and not exceeding half of the period in aggregate". If you write that in full every time you end up with information that is so long it's impossible to digest. If you don't, you might as well write "TEMPO".

[batninth]

XL319

wx is always crap at LBA

Rubbish, I've lived here for over 20 years and I can recall three or four occassions when it has been fine :). Actually I can recall a couple of times when it's been good (ie flyable) weather in Leeds but not up at the airfield further North.

I was up at Durham Tees Valley Airport the other day & one of the ATCOs said that they treat a PROB30 as "It might..." & a PROB40 as "It most likely will...". Not sure how much that was based on fact & how much was an interpretation. Anyone care to comment?

[whitehorse]

.......and don't forget that the wind direction is true not magnetic. For those of you who fly a little further a field, it makes quite a differance to the cross wind at the airport when considering landing/take-off. We don't all fly in areas with nearly zero variation. Ours can be up to nearly 60 degrees of variation.:}

[BackPacker]

......and don't forget that the wind direction is true not magnetic.

Wasn't it so that in METARs and TAFs the wind direction is true, while on the ATIS and whatever the TWR reports is magnetic, since runway headings are also magnetic?

After all, METARs and TAFs are used in flight planning, while you are still using true bearings and so forth. But in operating the flight you use magnetic headings so ATC gives the wind in magnetic too.

What about VOLMET?

[whitehorse]

Yes BP but it's usefull to remember when planning the flight, thats when you use the TAFs and METARS's. Volmets I'm sure are "true" .
WH

[Them thar hills]

Put more simply, if you can't see the windsock, it's raining.
If you can see the windsock it's going to rain !
I too was around Hebden Bridge helping to get the lights back on !
It was quite grimy in parts.
:hmm:

[Lasiorhinus]

If you get the winds in written form, TAFs, ARFORs, RSWTs, and so forth, the wind is given in degrees true.

If you get the winds in spoken form, ATIS, AWIS, Bloke in Tower, and so forth, the wind is given in degrees magnetic.

[bookworm]

If you get the winds in spoken form, ATIS, AWIS, Bloke in Tower, and so forth, the wind is given in degrees magnetic.

Not so generally. VOLMET is spoken and referenced to true north (verbatim METARs).

[bjornhall]

Because that would start to make flying accessable to all, and after spending £10k on a license I want to be special and able to decode those archaic runes.

Really tho', maybe that's not all that far off...? The type of short term, local and highly accurate (well... ;)) weather reports provided for free to pilots would be quite expensive if you wanted to order them from the met providers...

Ergo, the METAR/TAF codes are actually a form of encryption. Bet most PPL students would agree... :ooh:

[Chuck Ellsworth]

Why can't they just give the weather in plain English?

Is modern technology not capable of something that simple?

[whitehorse]

"Why can't they just give the weather in plain English?"

Chuck and others, maybe its because the whole world does not speak English. First the problem with translating it and secondly what does it mean in that region? At least with TAFs and METARs there are definitions of what each group means, which are available, translated into the local language.
It just takes application, practice and clarifying what it means with an instructor/experienced pilot, until you get the hang of it.

On the other hand they seem to have dummed the TV weather down so I supose a print out of pretty pictures would be OK!:E

WH

[Sepp]

A little-known group that you may see will go something like

TX30/14Z TN20/04Z

That would be max temp expected 30degC at 1400utc, min 20 at 0400

[Chuck Ellsworth]

Chuck and others, maybe its because the whole world does not speak English.

Hmmmm...

.....I thought that English was the international language of aviation.

Oh well, I guess it's back to reading the weather in code. :E

[bern444]

Chuck - if you go to ftp://tgftp.nws.noaa.gov/data/observations/metar/decoded/ you'll find that a rather unimportant tiny little weather organisation called NOAA thinks it is possible to give out decoded METARs on an offical site. No TAFs as yet though.

B

[bern444]

Excellent - thank you, I'll add a link to my site.


...so, basically NOAA, a not insignifcant player in the weather forecasting world, can manage to translate that which the British Met Office says they can't do. And NOAA is free at the point of use. Mmmm.


Bernie

[bookworm]

Hmm.

Aviation Digital Data Service (ADDS)
Output produced by METARs form (1812 UTC 10 July 2008)
found at ADDS - METARs (http://adds.aviationweather.gov/metars/index.php)

METAR text: EGSS 101750Z 22018KT 9999 FEW035 18/11 Q1005
Conditions at: EGSS (STANSTED AIRPORT, GB) observed 1750 UTC 10 July 2008
Temperature: 18.0°C (64°F)
Dewpoint: 11.0°C (52°F) [RH = 64%]
Pressure (altimeter): 29.68 inches Hg (1005.0 mb)
Winds: from the SW (220 degrees) at 21 MPH (18 knots; 9.4 m/s)
Visibility: 6 or more miles (10+ km)
Ceiling: at least 12,000 feet AGL
Clouds: few clouds at 3500 feet AGL
Weather: no significant weather observed at this time

If it's so easy, why does this translator make a patently invalid claim about the ceiling? :E

[NeuterCane]

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

[bern444]

Yes - something I hadn't quite grasped....the code which has to be a code because it's international, means different things in different countries.


Mmmmmm - again.

B

[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...:ok:

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] ([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 (http://secure.metoffice.com/aviation/taf_decode.jsp)
Metar decode; http://secure.metoffice.com/aviation/metar_decode.jsp (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 (http://www.nats-uk.ead-it.com/aip/current/gen/EG_GEN_3_5_en.pdf) para 12

[liam548]

UK GEN 3.5.10 (http://www.nats-uk.ead-it.com/aip/current/gen/EG_GEN_3_5_en.pdf) 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>