GRIB Atlas

Where to get GRIB files, which model to pick, and how to read them.

Pick a model first

Model	Run freq	Horizon	Resolution	Best for
GFS (NCEP)	6 h (00/06/12/18Z)	384 h	0.25°	Free baseline, global, longest view
ECMWF HRES	12 h	240 h	0.1°	Best mid-latitude skill; often paid
ICON (DWD)	6 h	180 h	0.125°	Free, solid in Europe/Atlantic
NAM / HRRR	hourly	18–84 h	3–12 km	US coastal/short range
WW3 / NWW3	6 h	180 h	0.25°	Wind waves + swell (sig wave height, period, direction)
RTOFS / HYCOM	daily	192 h	~1/12°	Ocean currents + SST

Rule of thumb: compare GFS + ECMWF. If they disagree at 72h, trust the pattern both agree on and widen your safety margin.

Full playbook (Saildocs + ftpmail, subscriptions, recipes): Email Request Playbook.

Email query@saildocs.com with body:

send GFS:35N,50N,135W,120W|0.5,0.5|0,6..72|WIND,PRMSL,WAVES

GFS: model. Also ECMWF:, ICON:, NAM:, WW3:.
Area: N lat, S lat, W lon, E lon.
Grid: lat step, lon step (use 1,1 to keep file small).
Hours: start..end with optional step (0,6..72 = 0, 6, 12, …, 72).
Params: WIND, PRMSL, PRESS, TMP, RH, GUST, WAVES, HGT500, CAPE, CLOUDS, PRECIP.

MSLP + wind at 10 m — the primary picture.
Gusts — add 30–40% to mean wind in unstable air; check gust field directly.
Significant wave height + period — long period (>10s) = swell, short (<7s) = local wind sea.
500 mb height — steering flow, watch for troughing upstream.
Precip + CAPE — squall potential.