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    Description of weather overlays

    Frequently Asked Questions
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    • 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
                                • Gkikas LGPZG
                                  Gkikas LGPZ Moderator @idefix37
                                  last edited by

                                  @idefix37
                                  What is "wind accumulation" ?
                                  I can not find any definition here
                                  http://glossary.ametsoc.org/index.php?title=Special:AllPages/W

                                  I've (also) just discovered this parameter and I see that is not changing
                                  for the whole forecast period.

                                  It reffers to the max wind for the forecast period?
                                  or to mean direction and wind speed for the forecast period?

                                  We can accumulate rain or snow, but ... wind? Is not stacked !

                                  TZT 1 Reply Last reply Reply Quote 1
                                  • TZT
                                    TZ Administrator @Gkikas LGPZ
                                    last edited by

                                    @gkikas-lgpz It is maximum intensity projection - means that maximal value of the forecast period is taken for each point.

                                    idefix37I 2 Replies Last reply Reply Quote 5
                                    • idefix37I
                                      idefix37 Sailor Moderator @TZ
                                      last edited by

                                      @tz
                                      @Gkikas-LGPZ
                                      Thanks, but strange that there has been no announcement and explanation for this new layer.
                                      It’s a way to predict the track of a strong and localised storm that’s OK. Is « Wind accumulation » the best name for this layer? But I’ve not another name to propose.

                                      TZT 1 Reply Last reply Reply Quote 0
                                      • TZT
                                        TZ Administrator @idefix37
                                        last edited by

                                        @idefix37 It was released quickly because of the current hurricanes and typhoons. Probably some adjustments will be made and we will also add the description.

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

                                          @tz
                                          Sorry the announcement was in the next post !

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

                                            @TZ
                                            Today there are 2 storm tracks in the North Atlantic:
                                            One is the track of Helene. The second one, it seems impossible to identify what makes it
                                            (Note that the tracks are black on my screen because I changed the wind colour settings: strong winds are black for me)

                                            0_1537039405024_234DA710-0391-46DD-A285-B224D5F1904E.jpeg

                                            On this track there is e.g. 154km/h at this point: N 57º16’ W16º36’.
                                            If the time slider is moved over the 10 days there are only 2 maximum at the same point: 95km/h on Wednesday and 104km/h on Sunday.
                                            So, how is it possible to have 154km/h and what is the explanation of this narrow track when there is no localised storm?

                                            TZT 1 Reply Last reply Reply Quote 0
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