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    "Surface" temperature/wind doesnt show earth's surface values

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    • S
      sPhoenix @idefix37 | Premium
      last edited by

      @idefix37

      Hi,
      sorry i didnt mention that i also selected the NEMS4 model at windy. And i made the observation that it shows completely different surface values than other weather websited that use the same models - in alpine areas.

      This was very evident during the past days with strong winds. The windity map just didnt show these high gusts speed that you'd expect on mountains - while other weather websites with same models delivered far better results.

      The Airgram helps here - like the elevation slider, but it doenst show the elevation of the model data for this position. In fact, it seems that the pressure scale is hard coded? Otherwise it wouldnt make sense that the air pressure scale f.e. at Mont-Blanc starts at 1000hpa. I'd first need to calculate the current air pressure at the real surface level there.

      I just felt the urge to give this feedback. Because despite the really nice frontend, the great usability of windy.com and the state-of-the-art weather models this is quite a weakness if you look for forecasts in mountain areas.

      Regards,
      Simon

      idefix37I 1 Reply Last reply Reply Quote 0
      • S
        sPhoenix @Gkikas LGPZ | Premium
        last edited by idefix37

        @Gkikas-LGPZ

        Thanks for the link. That's exactly the same issue in fact

        1 Reply Last reply Reply Quote 0
        • Gkikas LGPZG
          Gkikas LGPZ Moderator Meteorologist @sPhoenix
          last edited by

          @sphoenix
          The actual altitude for Garmisch is 707m, but the ECMWF's reference altitude for G-P is 1369 m !
          0_1516538698852_5b78575a-800a-4bba-b110-616060444413-εικόνα.png

          Also for Zugspitze (actual=2962 m , model's reference alt.=1700m).
          Difference 1262m, temp. adjustment - 4 C (aprox).

          S Gkikas LGPZG idefix37I 3 Replies Last reply Reply Quote 1
          • S
            sPhoenix @Gkikas LGPZ | Premium
            last edited by idefix37

            @Gkikas-LGPZ
            Thanks for this info.
            It would be great if these adjustment (model - actual) would be included at windy.com

            1 Reply Last reply Reply Quote 1
            • Gkikas LGPZG
              Gkikas LGPZ Moderator Meteorologist @Gkikas LGPZ
              last edited by

              I correct:
              Also for Zugspitze (actual altitude=2962 m , model's reference alt.=1700m).
              Difference 1262m, temp. adjustment - 8,2 C
              (as 6.5/1000 = 8.2/1262)

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              • idefix37I
                idefix37 Sailor Moderator @Gkikas LGPZ
                last edited by idefix37

                @Gkikas-LGPZ
                Hi,
                Could we know where do you find these graphics ?

                Gkikas LGPZG 1 Reply Last reply Reply Quote 0
                • idefix37I
                  idefix37 Sailor Moderator @sPhoenix
                  last edited by

                  @sphoenix
                  Yes it is a weakness in mountain areas, but ECMWF and GFS are global models designed to provide weather forecasts covering the globe, difficult to ask them for a better resolution. At least NEMS-4 must be more precise in alpine area... as claim Meteoblue. But difficult to see a difference with ICON-7. The best should be COSMO-1 (1.1km) covering the alpine arc, or AROME (1.3km) covering France and a little more.
                  My concern is more about the Freezing Altitude which is considered « above the ground » but not above the sea (amsl) by ECMWF and ICON. In mountain, in Germany, what is the Freezing Altitude reference, local ground or amsl?
                  Rgds
                  Alain

                  1 Reply Last reply Reply Quote 0
                  • Gkikas LGPZG
                    Gkikas LGPZ Moderator Meteorologist @idefix37
                    last edited by

                    @idefix37
                    From ECMWF's application named "Forecaster" but it is not for public use,
                    you have to log in.
                    .

                    idefix37I 1 Reply Last reply Reply Quote 0
                    • idefix37I
                      idefix37 Sailor Moderator @Gkikas LGPZ
                      last edited by idefix37

                      @Gkikas-LGPZ
                      thanks

                      1 Reply Last reply Reply Quote 0
                      • Gkikas LGPZG
                        Gkikas LGPZ Moderator Meteorologist @idefix37
                        last edited by

                        @idefix37
                        You said: "We have here the same problem, with -9ºC in Chamonix (1050m) and -11ºC on top of Mont-Blanc (4850m) !".

                        I made a small research and I provide you the data and conclusions
                        (for ECMWF model).
                        Chamonix: model's "surface" =2137m, elevation=1036m (Δ= 1101)
                        Mont-Blanc:model's "surface" =2265m, elevation=4808m (Δ= - 2543)
                        Temperature adjustment
                        Chamonix: +7,1C
                        Mont-Blanc: -16,5 C.
                        Those "adjustments" take into account Standard Atmosphere's lapse rate (6,5/1000m).
                        In the real world, the lapse rate may vary from 9,8 °C/km in dry air
                        to around 5 °C/km for moist air (into clouds).

                        Hope it helps

                        Gkikas LGPZG S idefix37I 3 Replies Last reply Reply Quote 0
                        • Gkikas LGPZG
                          Gkikas LGPZ Moderator Meteorologist @Gkikas LGPZ
                          last edited by

                          ... in the same way (adjustments in ºC) ...
                          for Vienna: +0,2 Innsbruck:+3,9 Praha: +0,4
                          Olympus Mt.peak (2917m), Greece: -10

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                          • S
                            sPhoenix @Gkikas LGPZ | Premium
                            last edited by idefix37

                            @Gkikas-LGPZ

                            Wouldn't it be even more accurate to use the result of the model for the exact elevation?

                            So for example Mont Blanc: The delta between ECMWF model elevation and real elevation:1101m:

                            So to get the estimated temperature/wind at the summit: use the closest calcuated value to 1101m above model surface. That's certainly also not 100% correct, because it doesn't take surface effects into account, but maybe more accurate than to assume ISA.
                            It don't have access to the ECMWF data, but here a snapshot from NEMS4 sounding for Mont blanc:
                            0_1516617214983_Capture.JPG
                            The NEMS4 model surface seems to be at ca 3200m according to this sounding, temperature around -5°C.
                            At 4800m it shows like -15°C. So a delta of -10°C in this case.

                            Regards,
                            Simon

                            Gkikas LGPZG 2 Replies Last reply Reply Quote 0
                            • Gkikas LGPZG
                              Gkikas LGPZ Moderator Meteorologist @sPhoenix
                              last edited by

                              @sphoenix
                              For Mont Blanc the Δ is 2543m

                              Gkikas LGPZG 1 Reply Last reply Reply Quote 0
                              • Gkikas LGPZG
                                Gkikas LGPZ Moderator Meteorologist @Gkikas LGPZ
                                last edited by

                                @sPhoenix
                                At the "sounding" :
                                3200m ... -5°C
                                4800m ... -15°C
                                4800-3200=1600m ..... ΔT=10
                                10/1600 = 6,25/1000m = ISA (almost !)

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                                • Gkikas LGPZG
                                  Gkikas LGPZ Moderator Meteorologist @sPhoenix
                                  last edited by

                                  @sphoenix
                                  Nice sounding! Is freely available ?

                                  S 1 Reply Last reply Reply Quote 0
                                  • S
                                    sPhoenix @Gkikas LGPZ | Premium
                                    last edited by idefix37

                                    @Gkikas-LGPZ

                                    Yes almost ISA in this case, but just an example. But in most cases the ISA temperature delta would be good enough problably.

                                    This graph is from meteblue, it's only available for point+ subscriber i think.

                                    Regards,
                                    Simon

                                    Gkikas LGPZG 1 Reply Last reply Reply Quote 0
                                    • Gkikas LGPZG
                                      Gkikas LGPZ Moderator Meteorologist @sPhoenix
                                      last edited by

                                      @sphoenix
                                      Thank you

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                                      • idefix37I
                                        idefix37 Sailor Moderator @Gkikas LGPZ
                                        last edited by idefix37

                                        @Gkikas-LGPZ
                                        Thank you. I took the example of Chamonix and Mont-Blanc temperatures just to underline the wrong temperature display by global models in mountain areas. You give the way to know the exact temperature, fine. But for me, just a quick look to the airgram, as you explained before, it’s enough precision.
                                        What I have found through these questions, that’s the worse terrain resolution of the global models compared to there atmospheric resolution. And this is not obvious, as Windy show a very precise terrain resolution, we expect the same precision from global models, but that’s impossible !

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