TEMPO in a METAR

[ranklein]

Hi,

Is it normal to see a TEMPO in a METAR?
I know a METAR basically is an observation of what's outside right now.
A TEMPO is like giving some kind of a forecast for the coming hour.

Here's an Ex:

METAR LLBG 260650Z 23006KT 9999 SCT020TCU BKN050 OVC100 15/12 Q1005
RERA TEMPO 24020G35KT 3000 TS SHRA SCT005CB=

Thanks!

[Wingswinger]

Yes. It's a trend forecast and it is valid for the next two hours from the time of the METAR. More usually there will be NOSIG(NS) or BECMG to indicate a change happening or not as the case may be. TEMPO means that there is definitely a change about to happen and it will be those conditions (in this case TS SHRA) for at least half of the two hour period from the time of issue of the METAR.

That's my understanding without going to look it up, anyway. HTH.

[Capn Bloggs]

In my part of the world, a METAR is just that; a Report. If there is any forecasting going on, then it would have to be in a TTF METAR, being a Trend Type Forecast (METAR+Trend), which overrules the TAF for the validity of the TTF ie 3 hours.

We would never see a forecast component, as shown in the first post, in a METAR.

[Der_dk.]

Hi

Over here in euroland (at least in Denmark) it is as Wingswinger mentioned.
So just one comment to that: A trend can only be put on a METAR if you have a meteorologist on the mentioned airfield.

regards

[sleeve of wizard]

Capn Bloggs,

Things are done differently in AUS, if memory serves correctly a METAR in AUS is valid for 3 hours.

As per JAR OPS a METAR is only valid for 2 hours and will have a trend attached, ie NOSIG etc

[bfisk]

As others have mentioned, this is a met observation with an appended short forecast, ie a trend. It should be interpreted as valid for 2 hours, and as per normal interpretation the TEMPO indicates a condition likely to occur for less than 1 hour at a time, and for less than 50% of the time totally.

[Capn Bloggs]

if memory serves correctly a METAR in AUS is valid for 3 hours.

Wrong, Sleeve.

[9.G]

I agree with wingswinger on this one as well as trend does overrule the forecast.
Little note one can still dispatch despite the trend being below the applicable minima for destination provided additional fuel for 1 hour is on board. That 1 hour fuel covers 1 hour of adverse weather.

[mssandvik]

I too agree with Wings. The TEMPO, BECMG and NOSIG explains the tendency at the time of the METAR.

The METAR reports the weather at the specific time, and if any significant change are to be expected the next hour, this will be presented as TEMPO or BECMG.

The TAF are issued only once every 3 hours, and I think we can all agree on weather often changing much quicker than this.

[AerocatS2A]

Things are done differently in AUS, if memory serves correctly a METAR in AUS is valid for 3 hours.

A METAR in Aus is just a report and has no validity period, it's simply a statement of conditions at a particular time. A TTF METAR on the other hand is a METAR with a trend attached, the trend is valid for three hours and supersedes the TAF.

The met report/forecast in the op is the equivalent of an Australian TTF METAR.

[seilfly]

In what publication will I find rules'n'regs for MET-messages? The respective national AIPs?

[AerocatS2A]

In what publication will I find rules'n'regs for MET-messages? The respective national AIPs

Yes, or the Jeppesen Manual or whatever other third party publication you may use.

[Checkboard]

The met report/forecast in the op is the equivalent of an Australian TTF METAR.

Not quite. In Europe, when a statement of trend is attached to a METAR, that trend forecast is valid for two hours, not the three of a TTF. The TREND is a forecast, and as such is valid for determining weather for the "one hour before and one hour after" requirement for the selection of alternates and the like.

UK AIP GEN 3.5 - 32

10.13 TREND

10.13.1 For selected aerodromes, this is a forecast of significant changes in conditions during the two hours after the observation time: a. Change Indicator: BECMG (becoming) or TEMPO (temporary), which may be followed by a time group (hours and minutes UTC) preceded by one of the letter indicators FM (from), TL (until), AT (at); b. Weather: Standard codes are used. NOSIG replaces the trend group when no significant changes are forecast to occur during the trend forecast period. Examples: BECMG FM1100 25035G50KT; TEMPO FM0630 TL0830 3000 SHRA.

[sleeve of wizard]

my memory is a bit hazy, haven't flown in AUS for a number of years, I do recall now that as mentioned TTF METAR were only valid for 3 hours.

[Col. James Braddock]

great interesting thread...

[AerocatS2A]

Not quite. In Europe, when a statement of trend is attached to a METAR, that trend forecast is valid for two hours, not the three of a TTF. The TREND is a forecast, and as such is valid for determining weather for the "one hour before and one hour after" requirement for the selection of alternates and the like.

Ah yes, by "equivalent" I didn't mean to imply exact equality. But the idea of a TREND and a TTF (TREND TYPE FORECAST) is the same even if the validity periods differ.

[CitationsRock4me]

is there any publication online to get info on international metar abbreviations n stuff?

[Henry VIII]

Europe - MetOffice
See electronic page 20 about Metar.
US - NOAA

Years ago I found a WMO Metar & TAF decoder in pdf format. It's in my laptop but I don't know how to attach it and url address doesn't work anymore.

[selfin]

Seilfly,

WMO Manual on Codes (pub. no. 306).

ManualCodes

(FM-15 = METAR; FM-16 = SPECI; FM-51 = TAF)

[Dekka]

The part I dont understand is if a METAR which is a report issued every 30 or 60 mins, is issued with a TTF, which in AUS is valid for 3 hours, what happens to the validity of that same TTF when the metar is updated in 30 mins time?