No color on Black Sea map

[GeoTuxMan]

I try to show currents from Black Sea on a map with streamlines.
But all streamlines are same color.
The map is here: https://syroco.rmri.ro/earth/index.html
I keep the original layer (Ocean Current -Great Barrier Reef) , to see the diference between layers.

The code from demo.js:

                                 `

                                              function initDemoMap() {
                          var Esri_WorldImagery = L.tileLayer(
                         "http://server.arcgisonline.com/ArcGIS/rest/services/World_Imagery/MapServer/tile/{z}/{y}/{x}",
                         {
                       attribution:
                       "SYROCO 2024" +
                         "NIMRD 'Grigore Antipa'"
                        }
                       );

                  var Esri_DarkGreyCanvas = L.tileLayer(
                 "http://{s}.sm.mapstack.stamen.com/" +
                 "(toner-lite,$fff[difference],$fff[@23],$fff[hsl-saturation@20])/" +
                 "{z}/{x}/{y}.png",
                {
                attribution:
                "SYROCO 2024" +
                "NIMRD 'Grigore Antipa'"
                 }
                 );

                var baseLayers = {
                 Satellite: Esri_WorldImagery,
                "Grey Canvas": Esri_DarkGreyCanvas
                };

              var map = L.map("map", {
             layers: [Esri_WorldImagery]
              });

             var layerControl = L.control.layers(baseLayers);
             layerControl.addTo(map);
             map.setView([43, 35], 7);

            return {
            map: map,
             layerControl: layerControl
             };
             }

            // demo map
            var mapStuff = initDemoMap();
            var map = mapStuff.map;
            var layerControl = mapStuff.layerControl;

             

                             $.getJSON("water-gbr.json", function(data) {
                              var velocityLayer = L.velocityLayer({
                             displayValues: true,
                             displayOptions: {
                             velocityType: "GBR Water",
                              position: "bottomleft",
                             emptyString: "No water data"
                                },
                             data: data,
                              maxVelocity: 0.6,
                             velocityScale: 0.1 // arbitrary default 0.005
                            });

                          layerControl.addOverlay(velocityLayer, "Ocean Current - Great Barrier Reef");
                           });

                            $.getJSON("currents_6Dec2024.json", function(data) {
                           var velocityLayer = L.velocityLayer({
                            displayValues: true,
                            displayOptions: {
                            velocityType: "GBR Water",
                            position: "bottomleft",
                            emptyString: "No water data"
                            },
                              data: data,
                             minVelocity: -0.5,
                             maxVelocity: 0.3,
                             velocityScale: 0.1 // arbitrary default 0.005
                           });

                             layerControl.addOverlay(velocityLayer, "Black Sea Current - Romania");
                               });

`

My current dataset: (blacksea.json)
[{"header": {"parameterUnit":"m.s-1", "parameterNumber":2, "dx":1.0, "dy":1.0, "parameterNumberName":"U_component_of_current", "la1":80, "la2":-80, "parameterCategory":2, "lo2":379.66, "nx":83, "ny":141, "refTime":"2023-11-07 13:55:00", "lo1":20}, "data":[-0.04,-0.05,-0.05,.....] {"header": {"parameterUnit":"m.s-1", "parameterNumber":3, "dx":1.0, "dy":1.0, "parameterNumberName":"V_component_of_current", "la1":80, "la2":-80, "parameterCategory":2, "lo2":379.66, "nx":83, "ny":141, "refTime":"2023-11-07 13:55:00", "lo1":20}, "data":[....]

[almamigratoria-netizen]

I only see a shortened verson of blacksea.json here in the comments, but I'm seeing a huge area (nearly global) and you're saying you're just looking at the Black Sea. I'm seeing nx,ny (which is good), but I'm not seeing any dx, dy in your JSON. windy.js isn't all that smart and (at least the version I use) doesn't create them by back calculating from la1, la2, lo1, lo2, and nx, ny. How are you generating your JSON? You probably want to use @cambecc's grib2json or check out @almamigratoria's grib2json alternatives if you have trouble running Java.

I'd also suggest you don't set a negative minVelocity (speed is always positive), and play around with the velocityScale, see if that buys you anything.

[GeoTuxMan]

I use a python script to extract data from netcdf file and save into json file.
Now the map it's ok: https://syroco.rmri.ro/earth/blacksea.html