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Gazer75

TAFs, and how AS use them

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Hi..Been looking at how AS read and use the TAF when I enable dynamic taf element.The following TAF is just one of many I have tested. I used online updates and using fs time instead of system time.HUEN 092150Z 100024 36004 8000 FEW021 FEW023CB BECMG 0406 VRB06KT BKN120 BECMG 0912 18010KT 7000 SCT120 BECMG 2124 36005KT CAVOKOnly metar close at this time is:HKEL 092100Z 17003KT CAVOK 13/08 Q1023Now if we sort the TAF a bit it becomes:HUEN 092150Z 100024 36004 8000 FEW021 FEW023CBBECMG 0406 VRB06KT BKN120BECMG 0912 18010KT 7000 SCT120BECMG 2124 36005KT CAVOKThis is what AS display as metar during different times I selected using FS Real Time. Also on the ground at the airport.At around 0100Z:HUEN 092100Z 04003KT 9999 SCT020 18/14 Q1021 NOSIG RMK AUTOGEN AS2004.5Then:HUEN 100139Z 04003KT BKN120 18/14 Q1021 RMK DYNAMIC TAF ELEMENTHUEN 100240Z 04003KT BKN120 18/14 Q1021 RMK DYNAMIC TAF ELEMENTHUEN 100341Z 04003KT BKN120 18/14 Q1021 RMK DYNAMIC TAF ELEMENTHUEN 100442Z 04003KT BKN120 18/14 Q1021 RMK DYNAMIC TAF ELEMENTHUEN 100543Z 04003KT BKN120 18/14 Q1021 RMK DYNAMIC TAF ELEMENTHUEN 100644Z 04003KT 7000 SCT120 18/14 Q1021 RMK DYNAMIC TAF ELEMENTHUEN 100846Z 04003KT 7000 SCT120 18/14 Q1021 RMK DYNAMIC TAF ELEMENTHUEN 101347Z 04003KT 7000 SCT120 18/14 Q1021 RMK DYNAMIC TAF ELEMENTThen another hour later in time:HUEN 092100Z 04003KT 9999 SCT020 18/14 Q1021 NOSIG RMK AUTOGEN AS2004.5Lets break it down into the TAF parts and see what AS do.HUEN 092150Z 100024 36004 8000 FEW021 FEW023CBThis part seems to be used only to figure out when the taf is valid. Wind, visibility and clouds are not used. Problem is that AS dont use the taf before its been over an hour into its time.BECMG 0406 VRB06KT BKN120Here AS use the clouds, but as you can see above the BNK120 part is used as soon as the taf becomes valid, and not 0406 as the taf indicates.BECMG 0912 18010KT 7000 SCT120In this part AS use the 7000 meter visibility and the scattered 12000ft clouds, but again to early as the above tests show.BECMG 2124 36005KT CAVOKNever used. AS revert back to the autogen metar.Hope I made everything as clear as possible :)I guess what I'm trying to show is that TAFs are only half way working at this time. There are many places in the world that dont issue metar during the night, and very rarely at day. But they still give tafs every now and then.My question would be if Damian can have a look at this and come up with a better solution?I have every confidence in your abilities and look forward to more updates :)Keep up the good work!JT

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Hi JT,It seems things are working correctly, this is how AS decides what to use:1) Only TAF ELEMENTS are considered, not the TAF valid time/surface observation.2) When the valid time of the TAF ELEMENT is CLOSER to the METAR valid time (as compared with current time via system or FS clock depending on your settings), AND the METAR is more than 1.5 hours old, also compared to current time, the TAF ELEMENT will engage. So even though it may say valid 04 to 06Z, if this is closer than the METAR valid time (2100Z) you're going to get the TAF. This happens at about 01:30 as you have noted.So what happens is the wx morphs early to the relevant TAF element when the METAR is considered out of date. In our experience this is more realistic than waiting until the exact time of the valid time (04:00Z in the example).What we will consider doing is adding an option in a future revision which enables "absolute TAF time computation" and will only activate such element when it is indeed within the valid time. Does this make sense, and do you feel this is the right approach?Thanks for your feedback!

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Thanks for the reply Damian.I feel stupid here now :) Guess I just expected something different. I am no real pilot so I wouldn't know how this work. Someone else will have to say if using absolute taf would be correct or not.Have one question though. The first part of the taf, do that tell the weather at the time of the report?Thank you.JT

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Just another thing I forgot to note in the first post.The wind never changes when using taf. Is that the way it should be? From what I can remember the wind was 04004 during the whole time.JT

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