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    Description of weather overlays

    Frequently Asked Questions
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    • Gkikas LGPZG
      Gkikas LGPZ Moderator @jwh
      last edited by

      @jwh
      For the source of SO2 data ....click ...
      0_1527573931458_69a4c7f2-385d-472b-a661-fe6d2ca57ea3-εικόνα.png

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

        @jwh
        https://community.windy.com/topic/5982/so2-actual-time-or-predicted

        1 Reply Last reply Reply Quote 0
        • IgorXXXmirrorI
          IgorXXXmirror
          last edited by

          What does it mean in lightning l / km ^ 2?

          IXMfoxPrower^_^;;

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

            @igorxxxmirror
            lightnings per square kilometer.

            1 Reply Last reply Reply Quote 3
            • T
              TomSlavkovsky API developers | Premium
              last edited by

              @Gkikas-LGPZ @IgorXXXmirror There is a mistake pointed out by ECMWF - it should be flash/km2/day.

              idefix37I 1 Reply Last reply Reply Quote 1
              • idefix37I
                idefix37 Sailor Moderator @TomSlavkovsky
                last edited by

                @tomslavkovsky
                If the unit is flash/km2/day, why does the map changes every 3 hours? Is it a sliding average over 24 hours? Looking to the way how thunderstorms move on the map every 3 hours, it seems surprising

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

                  @idefix37
                  ECMWF definitions:
                  https://software.ecmwf.int/wiki/display/FCST/45r1+new+parameters%3A+lightning+flash+density

                  I think windy uses "Averaged total lightning flash density in the last 3 hours (litota3)"
                  with unit conversions.

                  P.S. as the model's grid is 9x9 km, I propose to keep the original ECMWF density
                  (units of flashes per 100 sq. km per hour).
                  Windy converted values down to 1 sq. km,
                  but this is a "very small" area for lightning forecast
                  and maybe it is prone to larger errors.

                  idefix37I 1 Reply Last reply Reply Quote 2
                  • idefix37I
                    idefix37 Sailor Moderator @Gkikas LGPZ
                    last edited by

                    @gkikas-lgpz
                    Thanks for this information. However, I still can’t understand how the thunderstorm maps can change every 3 hours step if the parameter used is « per day » (which is the case of the 4 parameters described in the ECMWF document). These parameters are probably useful for statistical comparisons, but not for forecast.
                    And it’s what is explained in this document :

                    0_1530607573507_57905F25-5384-441D-A09E-CB90F43D6D74.jpeg

                    So the ECMWF provide probably data to Windy in [ flashes / 100km2 / hour].... to be confirmed

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

                      @idefix37
                      I don't know how windy computes the lightnings parameters provided on the picker.
                      Maybe is "flashes / 100km2 / hour", multiplied by 100 (to provide flashes per sq. km),
                      multiplied by 3 (to provide flashes in 3 hr timesteps).
                      Windy's developers know!

                      I have also to mention that flashes per sq. km per day, is a UNIT, not a parameter.
                      Think about "rain rate" (or intensity):
                      in a stormy day we may have (for a small time period) a "rain rate" of 500 mm/hr
                      but the total rainfall may be only 50 mm /24 hrs.

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

                        @gkikas-lgpz
                        I understand perfectly what does mean a rate of rain, or flashes density, per hour, or per day, or per 3 hours per day...
                        What bother me is the discrepancy between map displays and units supposed to be used.
                        In the screenshots below the weather picker (for the same place) shows:
                        At 17h, 0.04 l/km2
                        At 20h, 2.22 l/km2
                        At 23h, 0 l/km2

                        0_1530721438639_C6BDB437-8D54-4117-B23E-820862FC5B14.jpeg

                        Showing such a variation, I can’t imagine that these values are expressed per day.

                        And as you said, Windy’s Developers must know which units are really used.

                        Gkikas LGPZG 1 Reply Last reply Reply Quote 2
                        • Gkikas LGPZG
                          Gkikas LGPZ Moderator @idefix37
                          last edited by

                          @idefix37
                          This is a new product and we don't know much about it.
                          Personaly, I use it as an "light-moderate-heavy" indication
                          rather than arithmetic values.

                          1 Reply Last reply Reply Quote 2
                          • katesiscoK
                            katesisco @Gkikas LGPZ
                            last edited by

                            @gkikas-lgpz
                            I have trouble using Windy.com
                            I was able to just click on carbon monoxide and see but that ceases as the choice for CO is no longer there. What happened or what am i doing wrong?
                            katesisco@yahoo.com

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

                              @katesisco
                              Press "more layers"
                              0_1531834033951_87158022-a15e-4bc2-84a9-44e7e8797408-εικόνα.png

                              and then activate "CO concentration".
                              0_1531834169952_02844908-7363-4cb0-9f8f-5489a54a8c23-εικόνα.png

                              1 Reply Last reply Reply Quote 0
                              • M
                                Meridies @Eand
                                last edited by

                                @eand said in Description of weather overlays:

                                @ivo

                                Could you explain difference between:

                                • wawes
                                • swell 1
                                • swell 2
                                • swell 3
                                idefix37I V 2 Replies Last reply Reply Quote 0
                                • idefix37I
                                  idefix37 Sailor Moderator @Meridies
                                  last edited by idefix37

                                  @meridies
                                  @Eand

                                  As you probably know the shape of waves, in a given place, is a mix of different kind of waves:

                                  • The windsea (also called wind waves) is produced by the local wind.

                                  • The main swell is produced by a strong wind far away.

                                  • Secondary swells are produced also by winds far away but in other places.

                                  All of them have different heights, come from different directions and show different periodes (which is the time between 2 wave crests)
                                  Swell 1 is the main swell, swell 2 and 3 are secondary swells (the swell classification 1, 2, 3 depends on their respective heights)
                                  In this example below, Wind gives the direction of windsea. Swell 1 has a height of 0.6m and a period of 9 seconds.

                                  0_1532433836586_C4D96B18-4CD9-49E4-8BCE-75D80F835ACE.jpeg

                                  The best surf conditions correspond to a strong swell with weak windsea and secondary swells.

                                  A cross sea thrown up by a strong wind and a strong swell whose directions make an angle close to 90º gives hard conditions for navigation.

                                  1 Reply Last reply Reply Quote 5
                                  • W
                                    Windysky
                                    last edited by

                                    Also it would be appropriate to post a legend up on the main page about what each of the layer icons represent. In this list of descriptions there are no corresponding icons. The names of the layers did not appear in the version of Firefox I was using.

                                    1 Reply Last reply Reply Quote 5
                                    • MarienkaM
                                      Marienka @Gkikas LGPZ
                                      last edited by Marienka

                                      @gkikas-lgpz I am just working on it. Coming soon both in this post and on windy.com >> "about these data" section ("clock" icon).

                                      Best wishes
                                      ~ Marie

                                      1 Reply Last reply Reply Quote 28
                                      • B
                                        bhanudeepthi
                                        last edited by

                                        Hi ,
                                        I am trying to get data related to weather overlays()wind,wave height,current,current direction) in my application. My input parameters would be lat,long and datetime. Can anyone please advise how to implement using windy api

                                        1 Reply Last reply Reply Quote 0
                                        • Elmo19E
                                          Elmo19
                                          last edited by

                                          Is there a description of Wind Accumulation? Seems like it would follow this description from above

                                          "Rain accumulation: Total rain accumulation in the next hours or days."

                                          But I am seeing it change for the path of Hurricane Florence southward along the South Carolina and Georgia coasts, which matches the spaghetti model's adjustments I've seen as well.

                                          Is Wind Accumulation an indicating factor in those models I guess? Also is there a plan to add those as a layer to the Windy interface?

                                          Just added the app and started recommending to friends - very much enjoying it so far!

                                          idefix37I 1 Reply Last reply Reply Quote 1
                                          • idefix37I
                                            idefix37 Sailor Moderator @Elmo19
                                            last edited by idefix37

                                            @elmo19
                                            I’ve just discovered the Wind accumulation today, thank to your question !
                                            I don’t know if I’m right, but for me this layer is the wind accumulation on 10 days (?) for the model you have selected, nothing to do with «Spaghetti models » (that I prefer calling Multimodels forecast). It is probably not either the Ensemble Model, but just the standard Deterministic Model that is selected i.e. ECMWF, GFS or NAM. But this is to be confirmed.

                                            Gkikas LGPZG 1 Reply Last reply Reply Quote 1
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