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    Description of weather overlays

    Frequently Asked Questions
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    • IgorXXXmirror
      IgorXXXmirror @TZ last edited by

      @TZ Thanks

      IXMfoxPrower^_^;;

      1 Reply Last reply Reply Quote 1
      • Rani
        Rani @ivo | Premium last edited by

        @ivo

        When using wave overlay, I see a color key indicating wave height and also boxes with values in them with either- or~ before the value. These numbers never match the color key .

        Please explain.

        1 Reply Last reply Reply Quote 2
        • Atalantia
          Atalantia last edited by

          What means the 330 before 64km/h? 0_1507996931412_WindyScreen.png

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

            @Atalantia
            wind direction 330 degrees (coming from NorthWest)

            M 1 Reply Last reply Reply Quote 4
            • jmds
              jmds last edited by

              @ivo said in Description of weather overlays:

              Rain rate:

              I cannot see RAIN RATE in the settings ....

              1 Reply Last reply Reply Quote 2
              • alecloudenback
                alecloudenback | Premium last edited by

                Is there an overview of the meteograms that Windy displays for the forecasts? I am not sure of what some of the background colors and charts mean.

                sonnigekerstin 1 Reply Last reply Reply Quote 10
                • sonnigekerstin
                  sonnigekerstin @alecloudenback | Premium last edited by

                  @alecloudenback Me neither. I was searching for a manual to find out about the meaning of the different colors,graphs,pictograms etc....

                  edneff 1 Reply Last reply Reply Quote 12
                  • J
                    joalb @TZ last edited by

                    @tz What height does surface refer to? There would technically be no wind at the surface, so it must be some standard height above the ground (whatever the common reading instrument height is). What is that height? (i.e. 2m, 10m, 20m?). I'd like to use the data to estimate wind shear at a given location and using surface (0m) is not valid.

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

                      @joalb
                      Surface wind refers to 10m above model's surface.
                      Surface temperature refers to 2m.

                      For ECMWF datasets, see https://www.ecmwf.int/en/forecasts/datasets/set-i
                      For ICON, see chapter 6 (Global output fields) in
                      "Database Reference Manual for ICON"
                      https://www.dwd.de/SharedDocs/downloads/DE/modelldokumentationen/nwv/icon/icon_dbbeschr_aktuell.html

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

                        .... or scroll on top of this page

                        1 Reply Last reply Reply Quote 2
                        • J
                          jwh @ivo last edited by

                          @ivo From Leilani Estates Big Island Hawaii: what is the source of SO2 data? Satellite only? Any way to include data from ground monitors such as: http://weather.hawaii.edu/vmap/hysplit/ ?

                          Gkikas LGPZ 2 Replies Last reply Reply Quote 1
                          • Gkikas LGPZ
                            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 LGPZ
                              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
                              • IgorXXXmirror
                                IgorXXXmirror last edited by

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

                                IXMfoxPrower^_^;;

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

                                  @igorxxxmirror
                                  lightnings per square kilometer.

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

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

                                    idefix37 1 Reply Last reply Reply Quote 1
                                    • idefix37
                                      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 LGPZ 1 Reply Last reply Reply Quote 1
                                      • Gkikas LGPZ
                                        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.

                                        idefix37 1 Reply Last reply Reply Quote 2
                                        • idefix37
                                          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 LGPZ 1 Reply Last reply Reply Quote 0
                                          • Gkikas LGPZ
                                            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.

                                            idefix37 1 Reply Last reply Reply Quote 1
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