# Fog Atlas

> Fog climatology and verified fog forecasts for 3497 airports worldwide,
> built for EFVS flight operations and anyone asking "will it be foggy tomorrow?".
> Climatology: hourly METAR observations 2016-01-01 to 2026-08-15
> (Iowa Environmental Mesonet). Forecasts: NOAA/NWS National Blend of Models,
> recalibrated per airport and verified against live observations. Forecast
> percentages are published ONLY for airports whose calibrated model beat that
> airport's own climatology on live verification (215 airports currently);
> all issued forecasts are logged and scored — receipts at /fog/scorecard/.

Updated 2026-08-16. Pages rebuild daily; the forecast API updates hourly.
Citation: link the airport page. Not for operational use.

## Per-airport pages (start here)
- [Airport index](/fog/): all airports, linked
- Page pattern: /fog/{icao_lowercase}/ — e.g. /fog/ksfo/ — the first block is
  the current answer in plain language; a facts box carries climatology numbers
- Machine data: /fog/{icao_lowercase}/data.json — stable JSON per airport:
  identity (icao/lat/lon/tz), climatology (hours/yr, monthly hours, fog season,
  median event duration), the current baked forecast answer, and API links

## City pages
- [City index](/fog/city/): every city with a measuring station
- Page pattern: /fog/city/{slug}/ — US/CA/AU slugs carry a region suffix
  (/fog/city/san-francisco-ca/); each page names its measuring stations and
  takes its answer from the city's primary station
- Machine data: /fog/city/{slug}/data.json — stations list with per-station
  fog hours and forecast status, plus the same baked answer contract

## Live APIs (JSON unless noted)
- [/api/forecast](/api/forecast): hourly calibrated issuance, all covered
  airports — meta.cycle, meta.publicAirports (the verified list), per-airport
  fhrs + p rows [P(vis<1mi), P(<0.5), P(<0.25), P(below CAT I)] in percent
- [/api/metar?ids=ICAO](/api/metar): latest observations (NOAA AWC passthrough)
- [/api/scorecard](/api/scorecard): live verification — Brier skill vs
  climatology, pooled and per passed airport

## Reference
- [Verification & the publication bar](/fog/scorecard/)
- [Methodology](/#methodology) (in-app section; band definitions, honesty ledger)
- [Hourly climatology detail](/data/detail/KSFO.json): 12x24 month-by-hour grids per airport
- [Sitemap](/sitemap.xml)