dispatch weather requirements

[captain coldfront]

Quick question, cos it's much easier asking the combined knowledge of this data base than it is to plough through the books.

What weather conditions can be disregarded in the planning stage, in the TAF?

ie. prob30/40, tempo with limits and with no limits, gusts etc.

thank you

[PNY]

None of it can be disregarded for disptach planning purposes.

Even if the probability was as low as just 1% you would have to apply it (ie. the 1 - 2 -3 rule = 1 hour before to hour after the ETA, 2,000 foot ceiling and 3 s.m visibility)

I hope that helps. Good luck!

[SNS3Guppy]

What weather conditions can be disregarded in the planning stage, in the TAF?

None of it. You should consider all the weather when planning a flight.

However, when we look at the weather, we note the winds and the anticipated runway, and the expected visibility--can we fly the approach? I look at the ceiling...it's not controlling, but it may affect what we can do, and it's a factor in selecting an alternate, too. Any temporary (Tempo) should also be considered.

I'm interested in forecasts of convective activity, and the area weather, too.

[BOAC]

Not sure where you are 'coming from', CC, but the above info is incorrect under EU OPS which allow Probs of <40% to be 'ignored' as can gusts - 'mean wind' only required. TEMPO/BCMG must be considered.

HOWEVER - having been 3 times badly 'burnt' by crap met forecasts in my 40+ years, this Captain may choose to do otherwise.

[Ringi]

There is a table in JAR OPS 1.297 titled application of aerodrome forecasts to pre-flight planning. It includes details for destination, take-off alternate, etc. At a glance an example of something to disregard comes under the tempo and prob column. You may disregard forecast improvements in this category. It makes sense and errs on the side of caution not to anticipate an improvement in conditions if they only have a prob30 chance of occurring.

[Henry VIII]

If you operate under EU-OPS rules, HERE are the details, electronic page 40.

[Ringi]

Thanks Henry, that is the table I was referring to.

[Henry VIII]

There are "nice" details on that table...
Bye

[captain coldfront]

Maybe I didn't phrase the question as well as I could have.
It was the legal dispatch requirements I was looking at not the practical piloting aspects.
BOAC has some of the answers there I think, Thanks.

[Boingboingdriver]

Yes tempo/bcg must be taken into account for planning.
My dispatch is taking in account ceilings ALONG WITH vis to chose wether a second alternate should be used.ie 1500m vis and 200ft ceiling at alternate..a second alternate is added for fuel planning.
However it is up to the pilots to disregard the second alternate fuel uplift since only the visibility is affecting us.
Yes some airports start low vis procedures due to ceiling but thats another debate:-)

Capt std

[Henry VIII]

Hi CC, my be I misunderstanded your request, but in EU-OPS environment the above link table IS the legal dispatch requirements.

So, it is normal to receive OFP (or whatever you call it) according that considerations. It's up to the crew (to the Cpt) to apply more conservative consideration(s).
To be justified against the flt ops dept.

Ciao

[Wilton Shagpile]

OK, so if you look at that table, it implies that FOR LEGAL PLANNING PURPOSES you can disregard a TEMPO at the planning stage if it is connected to a condition such as a CB....however, not for a situation related to poor vis. etc.

Is that correct?

So. for example if you have vis. of say 1500m with a TEMPO of 300m then you need to consider it right??

But you can (for legal purposes) ignore a PROB TEMPO all the time right?