METAR and TAF-differences please?

[Lump Jockey]

What's the differences between these two? And when would you check them during your flight: prior take off or prior landing?
LJ

[jayteeto]

I'm not sure that you have thought much about finding the answer for yourself. Check the met office website and also get hold of an excellent free booklet called 'Get Met'. It explains everything and even tells you how to decode. We issue it to trainee police observers and they pick things up pretty quickly.
The simple answer to your question is:
TAF is a forecast for a set number of hours ahead and a Metar is actual weather at the time of issue.
You can check all of them before and during flight using methods shown in the GetMet booklet. Not much fun getting airborne and finding that you cant get back down!!

[Astra driver]

A METAR is a french acronymn for "Aviation routine weather report" and can be thought of as a report of what is happening now at the airport. The reports are usually taken every hour unless changing conditions dictate a special report. Metars are broadcast on the ATIS along with other pertinent airfield info such as runways and approaches in use.

A TAF is the french acronymn for "Aerodrome forecast" and is a forecast created every 6 hours for conditions expected during the following 24 hours at the airport.

Most pilots use both reports together to get a completete picture.

Obviously the Metar is most relavent for the departure airport as it tells you what is happening now, and its information is used in take off performance calculations. The departure TAF is also going to be refered to in order to be aware of any approaching conditions that may have an impact.

For the destination, the TAF is more relavent and is the deciding fractor in wether or not an alternate is required and if so, the alternate's TAF (along with that airports' facilities) will determine if it is a suitable alternate. Metars also play a factor here; by looking at a series of them and comparing them with the TAF one can see if the TAF is "telling the truth". Making this comparison enables us to see if the forecast weather is changing faster, slower or, in some cases is completely different from the forecast.

Timing is everything, it makes the most sense to check the Metars just after the hour, in order to get the most up to date as they are usually published shortly before or on the hour. TAFs are published at 0000z, 0600z, 1200z and 1800z.

Once airborne, a check of the destination weather is definitely in order during longer flights, or any time the TAF indicated rapidly changing conditions were possible.

This is just my personal technique but I think most of us use something like this along with checking the wealth of additional information and charts that are available.

[Spitoon]

Dunno about the French origin but I always thought that TAF stood for Terminal Area Forecast.

[Keygrip]

MET eorological A ctual R eport

T erminal A rea F orecast.

Curious to know what they would be in French.

Astra Driver - it would have been more acurate to say that IN THE USA the Metars are done every hour. There are lands outside the USA (honest) that don't do them hourly.

If LumpJockey had told us where his Tardis was parked, we might have been able to help more. Funny thing, humour (forgive the pun).

[Astra driver]

Key grip;

"There are lands outside the USA (honest) that don't do them hourly"

That's why I said "Usually taken on the hour". It's not uncommon for the Metars not to be updated if there are no significant changes.

As for the French origin of the names I may be mistaken, If I can find any info on that I will post it. I may just be I'm thinking of other abreviations such as BR (mist) and FU (smoke) which are French contractions and assumed it applied to the Taf and Metar.

[selfin]

http://www.wmo.ch/web/www/documents.html#CodeTables

'Get Met' is not exhaustive. Refer to above for complete analysis.

[Dusty_B]

In the UK METARs are generally issued every 30 minutes (obs are made at hr+20 and hr+50 so that they can be issued on the hour and half hour). If there is little change, or the finances aren't available(!), then this may decrease to hourly.

TAFs come in three forecast periods: 9hrs, 18hrs and 24hrs - but there is only one station in the UK (that I know of) that issues 24hr TAFs: RAF Brize Norton. The most common is the 9hr TAF. only selected larger stations will produce 18hr TAFs.

Civvie stations tend to issue for periods 1000hrs-1900hrs, 1300-2200 etc. Military stations issue 0900-1800, 1200-2100 etc.

[Evil J]

(Talking as a met observer)

METARs are done every half an hour as previuosly mentioned, but if nothing has changed then all that is required is to change the time in the METAR. I think most of the large places (we do where I work) have an automatic METAR dispatch so its not forgotten, but without that when we're busy it would be very easy to forget to dispatch the METAR which would mean that it would appear the weather is out of date-but if it hasn't changed much it doesn't make much odds...if that makes sense....

Now would someone like to discuss SPECI's!!!!

[Whipping Boy's SATCO]

No.

UK AIP GEN 3.5.4 para 7.1 (a) refers.

[PPRuNeUser0172]

Yeah mate check em after you land as it is totally useless to know what the weather is doing before you take off???!

Possibly the most rediculous question I have ever come across on PPrune..............

[Astra driver]

Keygrip;

From the NOAA website;

METAR is the international standard code format for hourly surface weather observations which is analogous to the SA coding currently used in the US. The acronym roughly translates from French as Aviation Routine Weather Report. SPECI is merely the code name given to METAR formatted products which are issued on a special non-routine basis as dictated by changing meteorological conditions. The SPECI acronym roughly translates as Aviation Selected Special Weather Report.

A2. TAF is the international standard code format for terminal forecasts issued for airports. The acronym translates to Terminal Aerodrome Forecast , and is analogous to the terminal forecast (FT) coding format currently used in the US.


I knew those Frenchies were involved in this somehow!

Astra.

(I'm working with one of my frog pilot pals as to the exact french wording, bet you can't wait...)

[ww2flyer]

I hope the other responders appreciate the wisdom and knowledge of astradriver! What he has stated is correct and it is quite obvious that a little more education is needed.:ok:

[Taildragger]

Lump Jockey... Looking at your profile, I think you may be winding us up.

[Whirlybird]

Yeah mate check em after you land as it is totally useless to know what the weather is doing before you take off???!


Dirty Sanchez,

The question was actually would you check them prior takeoff or prior landing. Checking a METAR before you land doesn't sound that stupid to me. I don't do it, but it makes sense logically. Maybe you should RTFQ before you criticise.

Wind-up or not, this has generated some useful stuff in what was becoming a totally yawn-inducing forum, at least some of the time.

[Dusty_B]

Astra driver, ww2flyer,

I'm afraid the NOAA has got it wrong then! I assure you that METAR does actually stand for METeorological Actual Report. This is where the other abrieviation "Actuals" comes from.

Don't tell the brits about weather: we invented it :}

[Kolibear]

Have you noticed how todays TAF is never the same as tomorrows METAR?

[Whipping Boy's SATCO]

kolibear, but it is. You must always take into account the ubiquitous "TEMPO PROB 30"

[PPRuNeUser0172]

Whirly one

My point was, why would you want to check the weather for your destination after you have taken off. IMHO bad airmanship, en route divs?, poor practice all round, but then again this is a private flying forum so anything seems to go........


I thankyou for pointing out the error of my ways however,

Yours

DS;)

[Astra driver]

"Why would you want to check destination weather after you have taken off?"

I dunno, maybe a small detail like the weather at the destination has gone below minimums, or the only runway has been notam'd closed because somebody landed one gear up. Usefull stuff to know I'd say....

By the way, shouldn't it be;

T erminal
A erodrome
F orecast

as opposed to

T erminal
A rea (?)
F orecast

I think some people are confusing the TAF with an A rea F orecast
(FA)

[The Ugly Fend Off]

Something that is probably of more interest to all aviators now is the change in the way that forecasters/observers now report met visibilityand changes therein. Could catch many folks out unfortunately. You may find that reported vis is far different from actual vis.

[DOC.400]

OK, so what's listening to VOLMET en route, if it isn't METAR prior to landing but after take off????

And isn't an ATIS a METAR?

DOC
PS I wish they'd go back to Octas.....

[Astra driver]

TUFO;

I would like to learn more about the differences between reported and actual vis. Would you care to post or offer a link?
Thanks! AD



The weather portion of an ATIS is from a METAR.

Who would have thought a thread on TAF/METARs would last this long!

[Chilli Monster]

Doc
OK, so what's listening to VOLMET en route, if it isn't TAF prior to landing but after take off????

And isn't an ATIS a TAF?
Both VOLMET and ATIS broadcasts are Actuals (METAR) - Not TAFs

Astra Driver

Have a read of this (http://www.caa.co.uk/docs/33/CAP493Amdt63.pdf) - the relevant reading is Supplementary instruction 3 / 2004

[DOC.400]

Ah Chilli -you spotted my deliberate error.......top of the class......mumble, mumble......:rolleyes:

:slapselfaroundface: :O

DOC

[Astra driver]

chili,

Thanks.

I guess you could say that link is a case of, "Be carefull what you wish for"!

Thanks again, AD

[Lump Jockey]

Taildragger, I don't think this is this first time I've been accused for something of this nature! BTW, what is a taildragger?!
LJ.

[vintage ATCO]

Wait until you get onto Prevailing Visibility (AIC 84/04) . . . :rolleyes: