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    Windspeed and direction different heights

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    • D
      danie | Premium last edited by

      I am not too sure how to use the wind direction/speed at different altitudes. Say for instance you take a location that is 5000' amsl and use the cursor to move the height to 6400 feet....does it mean that the altitude is 6400 feet above the 5000' elevation or does it mean 6400 feet amsl, in other words 1400 feet above ground (the 5000' location)?

      Gkikas LGPZ 1 Reply Last reply Reply Quote 2
      • Gkikas LGPZ
        Gkikas LGPZ Moderator @danie last edited by Gkikas LGPZ

        @danie
        the winds aloft are amsl.
        Actually (and more precisely) are the winds on standard isobaric surfaces.
        For example the wind at 5000ft is actually the wind in a "surface" of the atmosphere where the pressure is 850 hPa.

        Over mountains those "isobaric surfaces" may intersect* (cut) the orography (land surface).
        Thus, if you point on Everest and chose wind at diferent altitudes you'll find out that wind "stays the same" at all the levels from Om (msl) up to 8.000m.
        On the airgram you'll see no wind at low levels.

        "*" Actually, models isobaric surfaces "touch" models land surface.

        Hope the following image will help.
        0_1512113432184_6f6eb6ac-bde2-4df5-ba95-79f09c5ae72a-εικόνα.png

        1 Reply Last reply Reply Quote 7
        • Referenced by  idefix37 idefix37 
        • ondrejspilka723
          ondrejspilka723 | Premium last edited by

          @Gkikas-LGPZ

          I see some issue with meteogram wind strength.
          Look at the sample, at 2700 AMSL wind is 17m/s.
          But meteogram for the spot shows 4m/s, which is for 1000hPa theoretical height (underground).

          I clicked on the spot on map to get prediction for it's location and altitude.

          So, in my opinion, basic meteogram, doesn't reflect altitude, so it provides highly inaccurate predictions. Especially for paragliding pilots it is super important to consider wind strength at takeoff altitude.

          It is pretty tricky and the only way how to get strength for altitude is use Airgram or Wind layer at height.

          I believe this shall be fixed as it leaves quite a lot of space for misleading user.

          2f0f51ea-f8b1-4953-87a7-1816dd81c7c7-image.png

          3496dfcc-3240-4f3d-9505-192475ae113c-image.png

          idefix37 1 Reply Last reply Reply Quote 1
          • idefix37
            idefix37 Sailor Moderator @ondrejspilka723 last edited by idefix37

            @ondrejspilka723
            As there is no issue, try to understand the post of @Gkikas-LGPZ above.

            And this one too:
            https://community.windy.com/topic/4831/aviation-winds-aloft-on-airgram/4?_=1681921025576

            ondrejspilka723 1 Reply Last reply Reply Quote 1
            • ondrejspilka723
              ondrejspilka723 @idefix37 | Premium last edited by

              @idefix37 well there's still an issue that model shows 4 m/s at 10m above ground while reality will be 17 m/s and more

              But I understand model limitations. Hope we can agree on that.

              Thanks.

              idefix37 1 Reply Last reply Reply Quote 2
              • idefix37
                idefix37 Sailor Moderator @ondrejspilka723 last edited by

                @ondrejspilka723
                Which model are you talking about ?

                ondrejspilka723 1 Reply Last reply Reply Quote 1
                • ondrejspilka723
                  ondrejspilka723 @idefix37 | Premium last edited by ondrejspilka723

                  @idefix37 visible on printscreens, please check them...

                  idefix37 1 Reply Last reply Reply Quote 1
                  • idefix37
                    idefix37 Sailor Moderator @ondrejspilka723 last edited by idefix37

                    @ondrejspilka723

                    ECMWF has a 9km resolution, so in mountains….
                    In the location you show, at mountain top, it could be useful to check Airgram.
                    An try ICON-EU and Meteoblue.
                    Then if you measure wind at top of a cliff or a sharp summit weather models will never predict the right speed.

                    1 Reply Last reply Reply Quote 2
                    • Referenced by  idefix37 idefix37 
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