This is a sample application using Ionic 5 and Leaflet with leaflet-velocity.
Since it was a headache to implement leaflet-velocity with Ionic 5, I decided to make a new version of this plugin.
This npm package leaflet-velocity-ts is based on a typescript fork of leaflet-velocity made by Cyrille Meichel adding to it wind speed values on the map when the mouse is over a region and some other little fix.
npm i leaflet-velocity-ts --save

import 'leaflet';
import 'leaflet-velocity-ts';
declare var L: any;// Declare leaflet lib and plugin

Get it running

• Clone this repository.
• Run npm install from the project root.
• If you do not install the ionic CLI (npm install cordova ionic -g)

• Run ionic serve in a terminal from the project root.

  How to use it

  // Read JSON DATA and use it for velocity layer
  this.http.get('assets/wind-gbr.json').map(res => res.json()).subscribe(data => {
  let velocity = L.velocityLayer({
    displayValues: true,
    displayOptions: {
      velocityType: 'GBR Wind',
      position: 'bottomleft',//REQUIRED !
      emptyString: 'No velocity data', //REQUIRED !
      angleConvention: 'bearingCW',
      displayPosition: 'bottomleft',
      displayEmptyString: 'No velocity data',
      speedUnit: 'm/s'
    },
    data: data,
    maxVelocity: 10,
  });
  velocity.addTo(this.map);
  });