About
About Meteo-Fly
Meteo-Fly is built for transparent, model-aware weather interpretation for paragliding and hang gliding. It combines an interactive map with detailed meteogram panels for wind, cloud, rain, humidity, and lifted condensation level analysis.
Why was Meteo-Fly created
I wanted a single chart that brings together all the information needed to assess a flight day: wind, cloud, rain, humidity, and the lifted condensation level, while letting me pick the forecast models I trust. That combination was missing from the tools available for paragliding and hang gliding. Additionally, most projects in this space come with some plan for monetization and transparency is limited because their code cannot be accessed. In comparison, Meteo-Fly is and will stay free and open-source. Meteo-Fly is a pet project I wanted to share, and Open-Meteo makes it possible.
Full disclosure: I work for Open-Meteo in my day job.
The meteogram panel
The meteogram panel shows a stack of charts covering wind, cloud cover, precipitation, humidity, and the lifted condensation level. You can show or hide the panel from the map view.
Wind arrows
In the wind chart, solid arrows correspond to wind data that comes directly from the model's native pressure levels. Transparent arrows are interpolated between those native levels to provide smoother vertical resolution. Treat the transparent arrows as helpful guidance rather than hard measurements.
Lifted Condensation Level (LCL)
The LCL line is calculated from surface temperature and dewpoint using Espy's approximation: LCL ≈ 125 × (T − Td) meters. The chart adds local terrain elevation to express the result as an altitude above sea level.
When is this valid?
- Best for a well-mixed boundary layer on convective days.
- Less reliable with inversions, frontal layers, or widespread stratiform cloud.
- Convective effects such as upvalley flows or thermal plumes are not captured by this estimate.
Grid cell selection
Weather models provide data on a grid. Meteo-Fly lets you decide whether to always select the closest grid cell or whether a grid cell with a similar terrain height should be selected. The resulting grid cell, the model grid elevation, and the DEM elevation will be displayed on the map. Which mode is optimal depends on various factors, such as the model's grid resolution, the local terrain variability, and the conditions on a specific day (e.g. windward vs. leeward). Experiment with both modes to see which one provides more realistic forecasts for your location and conditions.
- Terrain-aware favors land grid cells around the selected point with a similar elevation.
- Nearest always picks the closest grid cell, even if it sits over water or the elevation does not match.
Multi-model comparison
Each model has its own grid resolution, vertical levels, and physics. Use the model selector to compare trends instead of looking for exact agreement. When models converge, confidence is higher; when they diverge, expect variability in the real world.
Map tiles
Map tiles are served by two awesome projects: the base map uses OpenFreeMap, while terrain and hillshade overlays come from Mapterhorn, an open-data project hosting high-resolution terrain tiles. Go check them out.
Data source
Meteo-Fly uses meteorological data from Open-Meteo. All forecast data is fetched directly in the browser and cached locally for offline access via the service worker.
Limitations
- Mountain meteorology, valley circulations, and rotor effects are not resolved by global models.
- For some models, cloud cover is derived from model humidity profiles; thin orographic cloud can be missed.
- All forecasts are guidance only. Always combine with live observations and local knowledge.
Open source
Meteo-Fly is open source software. The source code is available on GitHub.