skewt

Interactive Skew-T Log-P diagram for atmospheric sounding data, built with D3.js.

Install

npm install skewt

Quick Start

ES Modules

import { SkewT } from 'skewt';
import 'skewt/style.css';

const chart = new SkewT('#diagram');
chart.plot(soundingData);

CommonJS

const { SkewT } = require('skewt');

Script Tag (CDN)

<link rel="stylesheet" href="https://unpkg.com/skewt/dist/skewt.css" />
<script src="https://unpkg.com/skewt/dist/index.iife.js"></script>
<script>
  var chart = new skewt.SkewT('#diagram');
  chart.plot(soundingData);
</script>

Data Format

Input data follows the GSD Sounding Format. Each object in the array represents one pressure level:

const sounding = [
  {
    press: 1000.0, // pressure in millibars (hPa)
    hght: 173.0,   // height in meters
    temp: 14.1,    // temperature in °C
    dwpt: 6.5,     // dew point in °C
    wdir: 8.0,     // wind direction in degrees
    wspd: 6.173,   // wind speed in m/s
  },
  {
    press: 975.0,
    hght: 386.0,
    temp: 12.1,
    dwpt: 5.6,
    wdir: 10.0,
    wspd: 7.716,
  },
  // ...
];

All wind speeds must be provided in meters per second (m/s). The unit option controls the display unit only.

API

new SkewT(selector, options?)

Creates a new Skew-T diagram inside the given container.

| Parameter | Type | Description | |-----------|------|-------------| | selector | string \| Element | CSS selector or DOM element for the container | | options | object | Optional configuration (see below) |

Options

| Option | Type | Default | Description | |--------|------|---------|-------------| | unit | 'kt' \| 'kmh' \| 'ms' | 'kt' | Wind speed display unit | | margin | { top, right, bottom, left } | { top: 30, right: 40, bottom: 20, left: 35 } | Chart margins in pixels |

const chart = new SkewT('#diagram', {
  unit: 'kmh',
  margin: { top: 30, right: 50, bottom: 20, left: 40 },
});

chart.plot(data)

Plot sounding data onto the diagram. Draws temperature line, dew point line, and wind barbs.

chart.plot(soundingData);

chart.clear()

Clear plotted data (lines, barbs, tooltips) while keeping the background grid.

chart.destroy()

Remove the diagram from the DOM and release all resources (ResizeObserver, SVG elements).

convert(value, unit)

Utility function to convert wind speed from m/s.

import { convert } from 'skewt';

convert(10, 'kt');  // 19.4384
convert(10, 'kmh'); // 36
convert(10, 'ms');  // 10

Theming

The diagram uses CSS custom properties for easy theming. Override them on the .skewt-container element:

.skewt-container {
  --skewt-temp-color: #e74c3c;
  --skewt-dwpt-color: #2ecc71;
  --skewt-grid-color: #ddd;
  --skewt-zero-color: #aaa;
  --skewt-axis-color: #333;
  --skewt-barb-color: #333;
  --skewt-font-size: 11px;
  --skewt-tooltip-font-size: 10px;
}

Features

• Responsive — automatically redraws on container resize
• Multiple instances — each diagram has isolated SVG IDs
• Interactive tooltips — hover to see temperature, dew point, height, and wind speed
• Wind barbs — standard meteorological barbs (5–100 kt)
• Themeable — CSS custom properties for all colors and sizes
• Tree-shakeable — modular D3.js v7 imports
• Typed — ships TypeScript declarations (.d.ts)
• Dual format — ESM and CommonJS builds

Browser Support

Requires a browser with ES2022 support (private class fields). All modern browsers are supported.

License

MIT