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What is the actual usefulness of TAF to an airline pilot

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What is the actual usefulness of TAF to an airline pilot

Old 21st Nov 2020, 12:47
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c52
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What is the actual usefulness of TAF to an airline pilot

I understand if the forecast is for insufficient visibility or very high winds, or storms, but the rest of the time? Does it matter if there's drizzle or heavy rain? How much brain power do you spend working out the significance to your flight if there's a 40% probability that the weather will be rather worse for less than half the time period?

I imagine that besides TAF there's another source of information telling you the runway is expected to be under water or snow, or even that half a continent is expected to be snowbound.

For myself I look at TAF to get a better idea of how much rain to expect than I get from the public Met Office forecasts which are always for the worst likely case. I've spent too many fine days at home after the forecast has been for rain.
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Old 21st Nov 2020, 16:15
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The main use is not, most of the time, to decide if we will go or not, for most airlines that is decide by the dispatcher, or ops / OCC (depending where in the world you are and what system the airline uses). The general rule is that for +/- one hour of your expected arrival time at destination or alternate the weather must be forecast to be above specified limits depending on the type of approach to be used, and that information can only come from the TAF. Having looked at that we can then look at what fuel the flight planners have chosen and decide if we want more if, for example, the wind is forecast to change giving a runway change and maybe longer routing needing more fuel, or if visibility may drop with possible delays if LVPs are going to be in force. Quite often, depending on type of aircraft and route we may have a trade off between load we can carry (passengers/bags/freight) and fuel, just like in a light aircraft. As a rule company ops will want us to carry as little fuel as possible and we will want to carry as much as we can possibly justify (unless we’re managers or training captains !! ), so the TAFs are very necessary.
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Old 21st Nov 2020, 17:09
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c52
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Thank you - if it's about your fuel as well as limits I can see the usefulness of the information. Presumably you take a probability of 30% as being as good as certain.

I know I always feel badly done-by if the 10% probability of rain actually turns into rain, just as surely as I know I have no right to.
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Old 21st Nov 2020, 17:49
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That kind of depends upon what the change is, and personal judgement. If it’s prob 30 of blowing snow, 50 knot winds and 400 metres vis I’d probably assume it was going to happen and take extra fuel. However, if the forecast was blowing snow, 50 knot winds and 400 metres RVR with a prob 30 of 10 kts CAVOK I’d probably assume it wasn’t going to happen and still take the extra fuel.

The big difference is that if I’m going flying for fun a light aircraft then if I decide not to drive to the airfield and the weather turns out nice, or the other way around it doesn’t really matter, there’s always another day. In a commercial operation if the forecast is above landing minimas and the wind below the aircraft limits then we’re going, the TAF helps us to reduce the amount of stress that we encounter during the day...
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Old 21st Nov 2020, 21:00
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Much easier than that...

One line TAF that barely covers half the sheet of paper - we're going!

Ten line TAF - flight cancelled.....
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Old 22nd Nov 2020, 07:46
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I like that!!
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Old 22nd Nov 2020, 16:21
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It often pays to remember that a 'forecast is a semi-educated guess, and NOT a guarantee'
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Old 22nd Nov 2020, 19:06
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Originally Posted by ETOPS View Post
Much easier than that...

One line TAF that barely covers half the sheet of paper - we're going!

Ten line TAF - flight cancelled.....
If only that were possible.

A very experienced captain asked me when i was a fresh FO: "Why do you check the weather? we have to fly anyway..". And of course he was right, we have to fly anyway, but it still makes sense to check.

A quick scan of the TAFs gives a pretty good picture how the weather is most likely going to develop, which runways and approaches can be used, if we have to take another alternate or dispatch without an alternate.

According to the book we have to assume whatever has a 40% probability is going to happen, while we can disregard 30%, however, as mentioned above that would depend on the kind of weather, personal experience and willingness to divert.
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Old 22nd Nov 2020, 19:47
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What is the actual usefulness of TAF to an airline pilot

Its used by the Captain to decide if he wants the leg or not......
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