STF-DIR 3 Posted March 11, 2021 Share Posted March 11, 2021 Hello, i have planned a testflight LOWW-EDDE. During the preflight i try to calculate the T/O Performance in PFPX ( Topcat is also available ) During that i see some differences in the Weather forecast. The sources are Online ( NOAA ) in both , PFPX and also Topcat. What can be the reason for that ? See attached picture Edit: I hold the Mouse over the Header of LOWW bottom of the PFPX Takeoff calc Window and also there the Wind is different between the Tooltip Window and the Calculation Window. See another attached Picture Matthias Please login to display this image. Please login to display this image. Link to comment Share on other sites More sharing options...
srcooke 422 Posted March 11, 2021 Share Posted March 11, 2021 Hello Matthias, Firstly performance calculation within PFPX will use TAF data for your planned departure time therefor different to the metar string. You haven't shown the Topcat downloaded weather, at 0750Z this became 150/12 which is what you are seeing. Link to comment Share on other sites More sharing options...
STF-DIR 3 Posted March 11, 2021 Author Share Posted March 11, 2021 Hello, but i did a weather update in TOPCAT and PFPX hav always the actual weather, i mean there is no update to do. Forecast: Ahh, the Weater in the bottom of the PFPX Window is the Forecast ? .. ok, but where is that weather ? In Topcat i could not find it also not in the Weather windwo. I dont understand that i think. Matthias Please login to display this image. Link to comment Share on other sites More sharing options...
srcooke 422 Posted March 11, 2021 Share Posted March 11, 2021 3 minutes ago, STF-DIR said: Forecast: Ahh, the Weater in the bottom of the PFPX Window is the Forecast ? Yes, so the winds displayed in the PFPX performance calculator should be broadly inline with that of your departure time. Link to comment Share on other sites More sharing options...
STF-DIR 3 Posted March 11, 2021 Author Share Posted March 11, 2021 Hmm, but i am still confused with that ... sorry. So, the weather strings in RED is the actual wether in LOWW, left in PFPX and right in Topcat, bot atual. Must they not be the same, because both of them are wether and Taf ( if iam right ). But there are differences. The one in BLUE should be the Takeoff Weather because it it the T/O Calculation in Topcat ( or am i wrong ? ) I am confused... Matthias Please login to display this image. Link to comment Share on other sites More sharing options...
srcooke 422 Posted March 11, 2021 Share Posted March 11, 2021 LOWW 110750Z 15012KT CAVOK 03/M01 Q1016 NOSIG LOWW 110515Z 1106/1212 15008KT CAVOK TX12/1212Z TNM01/1106Z TEMPO 1111/1116 16015G25KT -RA TEMPO 1120/1124 -SHRA BKN050 FM120000 27012KT 9999 BKN040 TEMPO 1200/1204 28015G25KT -SHRA FM120400 28020G30KT 9999 SCT045 The blue entry is the current reported weather 'METAR' issued at 0750Z The red entry issued at 0515Z is the 'forecast' 'TAF' for the stated period with date and time ranges. First line from 11th 0600Z to 12th 1200Z There are then variations in that forecast period again denoted by date/time. Your performance calculation will be based on that expected as per your planned departure time. Personally I would be inclined to run the takeoff calculation as you prepare for departure. An OFP could be generated many hours prior to your flight and the weather may well differ to that of a forecast. Link to comment Share on other sites More sharing options...
STF-DIR 3 Posted March 11, 2021 Author Share Posted March 11, 2021 ahh, i see my mistake, sorry. The STD from the FPL was 1400 and now its 1000. So PFPX calculated correct. I changed that and now its equal. Thanks for explaining that !! Matthias Link to comment Share on other sites More sharing options...
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