wmo4677

WMO4677 describes the present weather as reported from a manned weather station using numeric codes ranging 00 to 99.

Working with these codes can sometimes be a bit of a pain since while the codes are broken down into loose continuous blocks (like range 00-49 denoting no current precipitation) knowing the type of precipitation, or its possible severity often involves defining your own lookup tables / metadata.

This library aims to provide:

• Lookup objects for retrieving the WMO4677 code number from a human-readable name
• Metadata about each WMO4677 code number including
  • Is there any current precipitation? And if so:
    • What possible precipitation types are involved? (A given code number may include several possible precipitation types, e.g. code 69 which refers to rain, drizzle, and snow)
    • What is the primary type of precipitation associated with this code number? (e.g. the above example for code 69, the primary type is rain)
    • How severe could this precipitation type be? (Code numbers may refer to multiple possible severities)
  • Is a dust or sandstorm currently occurring?
  • Is fog or mist currently occurring?
  • Is a thunderstorm currently occurring?
• Support for the canonical WMO4677 code table, as well as openmeteo's own interpretations of the WMO present weather codes. While you likely don't strictly need this library to deal with openmeteo as its representation is a much reduced subset you may find some value in the categorisations included.

Installation

npm i --save-exact wmo4677

Samples

Finding the code number for a given human-readable name

Depending on your use-case, you'll want either the wmo4677 codes, or the openmeteo codes.

import { openmeteo, wmo4677 } from 'wmo4677';

// 66
const openmeteoCodeNumber = openmeteo.codes.FREEZING_RAIN_LIGHT;
const wmo4677CodeNumber = wmo4677.codes.RAIN_FREEZING_SLIGHT;

Finding the metadata for a given code number

As above, this depends on whether you're using wmo4677 directly, or the openmeteo codes.

Metadata is indexed by the code number - if you already have the code number e.g. from an API, you can use that - otherwise you can still look up the code number using its human-readable name.

import { openmeteo, wmo4677 } from 'wmo4677';

/*
  {
    code: 66,
    description: 'Light freezing rain',
    dustOrSandstorm: false,
    fogOrMist: false,
    key: 'FREEZING_RAIN_LIGHT',
    possiblePrecipitationSeverities: ['slight'],
    possiblePrecipitationTypes: ['rain'],
    precipitation: 'current',
    primaryPrecipitationType: 'rain',
    thunderstorm: false,
  }
*/
openmeteo.metadata[66];
openmeteo.metadata[openmeteo.codes.FREEZING_RAIN_LIGHT];

/*
  {
    code: 66,
    description: 'Rain, freezing, slight',
    dustOrSandstorm: false,
    fogOrMist: false,
    key: 'RAIN_FREEZING_SLIGHT',
    possiblePrecipitationSeverities: ['slight'],
    possiblePrecipitationTypes: ['rain'],
    precipitation: 'current',
    primaryPrecipitationType: 'rain',
    thunderstorm: false,
  }
*/
wmo4677.metadata[66];
openmeteo.metadata[wmo4677.codes.RAIN_FREEZING_SLIGHT];

Getting precipitation severities

A given code number may (when dealing with WMO4677) correspond to several potential severities. The library currently returns an array of all possible severities, but includes helper functions for getting the highest (i.e. worst) possible severity as well as the lowest (i.e. least bad) severity for a given weather code's metadata.

(You may not need this when dealing with openmeteo as none of its code points contain this ambiguity.)

import {
  highestPossiblePrecipitationSeverity,
  lowestPossiblePrecipitationSeverity,
  wmo4677,
} from 'wmo4677';

const wmo4677Metadata =
  wmo4677.metadata[wmo4677.codes.RAIN_OR_DRIZZLE_AND_SNOW_MODERATE_OR_HEAVY];

// ['moderate', 'heavy']
wmo4677Metadata.possiblePrecipitationSeverities;

// 'heavy'
highestPossiblePrecipitationSeverity(wmo4677Metadata);

// 'moderate'
lowestPossiblePrecipitationSeverity(wmo4677Metadata);

Rendering an appropriate weather icon for openmeteo

N.B. If using the full WMO4677 code space rather than openmeteo you may need to handle additional precipitation types like hail or ice, and the codes relating to cloud cover may have different interpretations.

import {
  highestPossiblePrecipitationSeverity,
  openmeteo,
} from 'wmo4677';

// See https://www.npmjs.com/package/openmeteo for `openmeteo` API package / info
const { currentWeatherCode } = await getWeatherCodeFromOpenmeteo({ lat, long });

const weatherCodeMetadata = openmeteo.metadata[currentWeatherCode];

if (weatherCodeMetadata.thunderstorm) {
  return <ThunderstormIcon />;
}

if (weatherCodeMetadata.dustOrSandstorm) {
  return <DustStormIcon />;
}

if (weatherCodeMetadata.fogOrMist) {
  return <FogIcon />;
}

if (weatherCodeMetadata.precipitation === 'current') {
  const { primaryPrecipitationType } = weatherCodeMetadata;
  const highestPossibleSeverity = highestPossiblePrecipitationSeverity(weatherCodeMetadata);

  switch (primaryPrecipitationType) {
    case 'drizzle':
      return <DrizzleIcon severity={highestPossibleSeverity} />;
    case 'rain':
      return <RainIcon severity={highestPossibleSeverity} />;
    case 'snow':
      return <SnowIcon severity={highestPossibleSeverity} />;
  }
}

if (
  weatherCodeMetadata.code === openmeteo.codes.OVERCAST
    || weatherCodeMetadata.code === openmeteo.codes.PARTLY_CLOUDY
    || weatherCodeMetadata.code === openmeteo.codes.MAINLY_CLEAR
) {
  return <CloudyIcon />;
}

return <ClearSkyIcon />;

Contributing

While contributions are appreciated, they may be rejected if not in line with the intended project direction. It's recommended to check before undertaking a major piece of work and/or refactoring.

Contributions should be based off the develop branch, and any pull requests made into develop.

Pull requests should include a corresponding entry in CHANGELOG.md.

Feedback and Support

For suggestions, issues, and/or support raise a GitHub issue!