isd_synop

NOAA Global Hourly (ISD) station observations via the anon S3 CSV mirror. ``s3://noaa-global-hourly-pds/<year>/<station>.csv`` — one CSV per station-year, keyed by USAF+WBAN id (default ``16741099999`` = Athens Eleftherios Venizelos). The file used to be handed to ``cfgrib``, which cannot read CSV, so every run fell back to synthetic data. Emits ``isd_t2m`` (°C, from ``TMP``) and ``isd_wind_speed`` (m/s, from ``WND``), hourly, dropping missing sentinels and suspect/erroneous QC codes. Each station-year file is ~1 MB (capped at :py:attr:`max_file_bytes`). The mirror lags: as checked on 2026-09-30 the newest year is 2025, ending 2025-08-24 (NCEI's own access service returns nothing later either). A missing year file is logged and reported in ``missing_years``. Recent-window fallback: hours inside the last :py:attr:`metar_days` days that ISD does not cover are filled from the station's routine METARs via the public aviationweather.gov API (NWS, no key; it serves 30 days only). Those are the same observations ISD ingests as ``FM-15``, but at METAR precision — whole °C and whole knots — and they are counted in ``metar_hours``. Hours older than that and missing from ISD stay empty. Needs the station's ICAO code (``icao``; known for the default station, ``""`` disables the fallback).