Modern web mapping technologies implement web standards that make the visualization of geoscience data on the web possible using various methods, offering a high degree of customizability for creating web maps. In meteorology, synoptic surface weather charts serve as crucial products to communicate observed surface weather at a point in time. To convey such information, these maps implement complex symbology, such as a multi-element surface station model symbol to indicate station data, isobars, and special line symbology to visualize weather fronts. Synoptic messages (SYNOP standard numerical code by WMO) are periodic meteorological reports of weather observations, exchanged by national meteorological services around the globe. This study focuses on visualizing surface weather data decoded from SYNOP reports. The paper introduces an open-source JavaScript module, which handles data decoding and dynamic symbol generation, using a WMO-compliant method for creating station model vector symbols for observational GeoJSON data on the client-side, in an interactive web mapping environment. Its output is compatible with popular, open-source web mapping libraries. It runs Python in the browser with Pyodide and makes use of the Web Workers API for parallelization, speeding up the decoding and visualization process without blocking the user interface thread. The developed module intends to help with easy representation of surface weather observations on web maps used in meteorology, which can also be implemented in a dynamically updated server–client architecture. The code is presented with a ready-to-use wrapper for Leaflet.
Balla et al. (2026) studied this question.