Location: Liverpool based Geordie, so calm down, calm down kidda!!
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!!
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.
"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.
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.
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....
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!
(I'm working with one of my frog pilot pals as to the exact french wording, bet you can't wait...)
Last edited by Astra driver; 4th Nov 2004 at 19:38.
Yeah mate check em after you land as it is totally useless to know what the weather is doing before you take off???!
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.
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,
"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