TEMPO in WX forecast?

[bigduke6]

Was having a bit of a discussion with an Instructor Pilot the other week.

I had always considered "chance of" under the old FAA wx forecast, or "TEMPO" in the current version, to be a valid/binding condition at the destination or for choosing an alternate airport or required fuel. His position was that I had been doing it wrong for years, and chance/TEMPO was so short term, that it did not matter per the regs, and that LEGALLY (not talking about good conservative practices) no fuel had to be included to account for the condition actually happening.

My position is that if you arrive, and the "temporary" below minimums wx that was forecast has occurred, you did not take off with the legal amount of fuel.

FAA says you need fuel "considering weather reports and forecasts and weather conditions"

"TEMPO: Indicator of temporary fluctuations to forecast
meteorological conditions which are expected to last less than
1 hour in each instance and, in the aggregate, to cover less than
half of the indicated period. In general, the period of time
covered by a TEMPO group should not exceed 4 hours."

So is TEMPO a valid forecast consideration, or is it just for background info, and is not legally binding?

Not really looking for opinions, but does anybody have any references to regulations for USA, Europe, or China/Asia?

[Mansfield]

The catch phrase within the US FARs is "weather reports, forecasts, or any combination thereof".

Excerpt from FAA Order 8900.1, Flight Standards Information Management System:

3-2049. POLICY ON CONDITIONAL PHRASES IN REMARKS PORTION OF
WEATHER FORECAST.
A. Weather forecasts provided by the National Weather Service (NWS) and other
sources often have conditional phrases such as “occasional,” “intermittently,” “chance of,” or
“tempo” in the remarks portions of the forecasts. These phrases supplement the main body of the
forecast by indicating the probability of changing conditions during the forecast period. These
modifying phrases, used in the remarks portion of a terminal forecast (FT), indicate the weather
conditions for an area within five nautical miles of a runway complex. Certain regulations
concerning the selection of destination and alternate airports require that “weather reports or
forecasts, or any combination thereof, indicate that the weather conditions will be at or above...”
the minimum weather conditions specified in those regulations. The FAA Office of Chief
Counsel has consistently interpreted these regulations to mean that the worst weather condition
in any of the reports or forecasts used to control a flight movement is the controlling factor.
These interpretations make the remarks portion of a forecast as operationally significant as the
main body of the forecast. Therefore, it is FAA policy that the worst weather condition in the
main body or the remarks portion of a terminal forecast, as well as any weather report used, is
the controlling factor when selecting a destination or alternate airport.

All due respect to the instructor, this has been around for years...it was in 8400.10, the Air Carrier Inspector's Handbook, before that document was rolled into this new one. You can dig this up on the web.

Indeed, there are actually ATA exemptions designed to end run this.

[Capn Bloggs]

Geez you yanks make life complicated. :p

[Ex FSO GRIFFO]

Hey Mr Bloggs,

Maybe THIS is where RHS gets his 'dickspeak' from...??? :eek::eek:

[Capn Bloggs]

I reckon you might be right, Griffo! :{

[ggofpac]

I might be wrong but i don't think it's illegal. U got diversion fuel- so if indeed when u arrive the wx is bad u can always divert. Tea and biscuits with Fleet is another matter as to why u choose not to carry extra to cover for the tempo.
But if its a diversion airfield that u are talking about...then don't nominate it....choose another alternate.

[bigduke6]

Mansfield, Thank you.

That was what I was looking for. I had been told years back that some carriers, like American Airlines, had an exemption but that it applied to everyone without said exemption. Hate to think I had been doing it wrong for the last 20 years!:ugh:

Any idea of outside the US, ie Europe or Asia?

[Checkboard]

Europe simply states, in EU-OPS: an hour before arrival until an hour after the planned arrival time, weather must be above the minima.

ICAO ANNEX 3 contains a table, included in our Ops Manual, which states that TEMPO is not applicable for planning for transient conditions (thunderstorms, showers etc) but must be considered for persistent conditions (fog, sandstorm, continuous precipitation) and also that forecast gusts may be disregarded.

In Australia, a TREND below the minima gives you the option of carrying 60 mins weather holding, or diversion fuel. ("INTER" allows 30 mins holding, or diversion fuel.)

[plain-plane]

Here is something from euroland

Enroute alternates: I MAY disregard gust values exceeding our wind limits, and in connection with transient conditions: I.e. TS, showery I may also disregard the mean wind exceeding our wind limitations…

Transient conditions, as above, are marked as not applicable in the ops manual when it comes to interpretation of wx at BOTH destination and destination alternate... :ouch:

[Mansfield]

Transient or persistent? 60 minutes with a TEMPO but only 30 with an INTER? Did someone say that we Yanks make things complicated? :)

Not to be outdone, however, we do have the exemption. This is ATA Exemption 3385. It is available to any operator who can convince their certificate management office to issue an ops spec for it, but is most commonly found with the large carriers as BigDuke6 had mentioned. The actual language is a bit hard to find, but I have pasted it below from a 2001 Nick Sabatini letter. It almost inevitably adds one to two hours onto any ground training program!

The upshot is that with this, you can accept weather forecasts down to one half of the standard requirement, provided you tack on an extra alternate that meets all of your standard requirements. Why you wouldn't do that in the first place is clearly a discussion for the accounting department.


Each certificate holder must list one additional alternate airport in the dispatch release whenever the METAR, TAF, or any combination thereof for the destination airport or first alternate airport indicate, by the use of conditional words in the remarks section of such METAR or in one or more time increments of the TAF, that the forecast weather conditions for the destination and the first alternate airport could be less than the authorized weather minimums for those airports. However, the METAR or TAF must indicate in another time increment that the weather conditions for the destination, first alternate, and second alternate airports are forecast to be not less than the applicable authorized weather minimum values as follows:
(a) With respect to the destination airport, the forecast weather conditions must not be less than one-half of the lowest weather minimum visibility value established for the instrument approach procedure expected to be used for an instrument approach at the destination;
(b) With respect to the first alternate airport, the forecast weather conditions must not be less than one-half of the alternate weather minimum ceiling and visibility values specified in the certificate holder's operations specifications for that airport; and
(c) With respect to the second alternate airport listed in the dispatch release pursuant to this exemption, the METAR, the appropriate time increment of the TAF, or any combination thereof for that airport must indicate in the main body and remarks section of the METAR or TAF that the forecast weather conditions will be at or above the alternate airport weather minimum ceiling and visibility values specified in the certificate holder's operations specifications for that airport. :ugh:

[bfisk]

Well, to take the guesswork out of this, our ops manual include a deciphering table to see what needs to be taken into account and what doesn't, and for what conditions. With regards to a TEMPO in a TAF it essentially says the following:

For an improvement in conditions, disregard the improvement.
For a deterioration on destination, disregard if it's a shower, otherwise consider.
For a deterioration on an alternate, add 1 hour fuel if shower, otherwise consider.

This from memory and it's late, so bear with me if I mixed it up. It's in our quickref anyway ;)

[Checkboard]

To illustrate the differences, imagine an airfield with a single north/south (00/18) runway, a CAT 1 ILS with a 200' minma, and an NDB with a 600' minima.

In Australia the chart would also show an "Alternate minima" of about 1100' (about 500' above the second lowest minima)

TAF 010/15 BKN 4500 15/3 1013

In Europe, you would require a single alternate (because of the single runway).

In Australia, you could plan with just destination fuel (cloud base above the Alternate minima, no CBs)

TAF 010/15 BKN 1500 15/3 1013 TEMPO SCTCB1200 TSRA

In Europe you would still require a single alternate (not because of the TEMPO, but still because of the single runway)

In Australia, you would now require either 60 minutes holding, or an alternate (thunderstorms count, even above the alternate minima).

TAF 010/15 BKN 1500 15/3 1013 TEMPO BKN 0100
(i.e. TEMPO below the landing minima)

In Europe you may disregard this tempo, and still only carry a single alternate - of course this carries the risk that the weather is actually present on arrival, requiring a divert. Any holding is at the pilot's experience/discretion.

In Australia, 60 mins or an alternate, as above.

TAF 010/15 BKN 0100 15/3 1013
(i.e. weather continuously forecast below the minima)

In Europe you may plan to this destination, but require TWO alternates. (This means the option of two alternates on arrival - i.e. carry fuel for the second closest, rather than the closest, as opposed to flying to the alternate, then flying to the second alternate.)

In Australia, planning to this destination at all is probably not permitted under CAR 257.

In summary: the whole "disregard the TEMPOs" bit in Europe is about how many alternates you need plan to carry. In Australia most operations DON'T plan an alternate at all - so TEMPOs need to be accounted for to ensure that alternates or sufficient holding fuel IS carried when needed.

In Europe the alternate need only have a cloud base higher than the second most limiting approach (i.e. CAT 1 minima, if you are CAT 3 approved.) In Australia, the alternate needs weather above the alternate minima - a mich higher value (about 500 feet above the second approach, and without CAT 3 in Australia the second highest is invariably a non-precision approach).

In Erope destination only fuel is only permitted if the weather is VFR, and two independant runways with two independant approaches are available. In practice this is never used, and an alternate is carried on every flight - even CAVOK days. In Australia, destination fuel is the norm, and alternate fuel is only carried on the odd occaision when weather turns up.

[Wizzaird]

I think your cloud base abbreviations have gone a bit astray:} BKN at 100ft is BKN 001 not BKN 0100 (which is 10,000ft!) But we knew what you meant:)

[bfisk]

In Erope destination only fuel is only permitted if the weather is VFR, and two independant runways with two independant approaches are available. In practice this is never used, and an alternate is carried on every flight - even CAVOK days.

I beg to differ. It can be, and is, regularly used, when practicable. Like any other procedure it has it's advantages and limitations, but it is indeed used from time to time.

TAF 010/15 BKN 1500 15/3 1013 TEMPO BKN 0100
(i.e. TEMPO below the landing minima)

In Europe you may disregard this tempo, and still only carry a single alternate - of course this carries the risk that the weather is actually present on arrival, requiring a divert. Any holding is at the pilot's experience/discretion.
Assuming you mean BKN015 TEMPO BKN001, that does indeed have to be considered as BKN001, at least where I work (which is in Europe).

In Australia, planning to this destination at all is probably not permitted under CAR 257.
What if you're going A to B, and B is forecast below operating mins. Can you then file a flightplan to C with alternate D, both being above alternate mins, start out on that flight, and then change your destination enroute (to B), if the weather at B clears up to permit approach?

[Checkboard]

My bad with the heights :O I was writing that in a hotel in a hurry before departure on a foreign keyboard. Thought of it as I left, but had no time to correct it.

Should have said that in my operation the destination fuel only procedure isn't really used in practice. The only destination it is worth it is Madrid (many runways, long diversion distances, for Europe at least). The TEMPO at 100 feet as I stated above is an Ops Manual thing, other operations may differ (as yours obviously does). As our operation is in Europe, it must therefore be acceptable to disregard it - your operation doesn't, and applying a higher standard is fine. :ok:

In Aus, CAR 257 is little understood. Most would plan to fly there, and carry an alternate.

[OzExpat]

How do you manage to keep both sets of regs straight in yer head after all this time, mate? I doffs me me hat to you because I no longer have the vaguest clue about Oz requirements after all my years in PNG.

[4dogs]

Checkboard,

I would be interested in your expansion of your comments on CAR 257. :hmm:

Stay Alive...

[bookworm]

ICAO ANNEX 3 contains a table, included in our Ops Manual, which states that TEMPO is not applicable for planning for transient conditions (thunderstorms, showers etc) but must be considered for persistent conditions (fog, sandstorm, continuous precipitation) and also that forecast gusts may be disregarded.

Where is it in Annex 3 please? I've only ever seen it (and I think it's the table you're thinking of) in JAR-OPS1 AMC/IEM.