GFS Explorer

The Global Forecast System is NOAA's flagship global model, run four times a day out to sixteen days. This page carries the first ten: hourly to F120, then three-hourly to F240 — 161 frames, which is the model's own publishing cadence rather than a limit imposed here.

These charts are drawn from the GFS surface-flux files, not the more commonly used 0.25° product files. That is a resolution decision: the flux files sit on the model's own 3072×1536 Gaussian grid at 0.117° — about 13 km — where the 0.25° product is an interpolation of the same forecast onto a grid twice as coarse. A 13 km rain core really is more intense than the 25 km field that smooths it.

The price is that two fields have to be derived, because the flux files carry neither. Dewpoint is computed from 2-metre specific humidity and surface pressure; checked against the GFS's own published dewpoint it agrees to within a fifth of a degree over 92% of the planet. Precipitation is integrated from the model's mean precipitation rate, whose averaging window restarts every six hours — both the per-step and the run-total fields come out within a few tenths of a percent of the GFS's own accumulations.

Wind direction rides on its own overlay — barbs, arrows or animated streamlines — and can be shown over any field, so you can watch the flow that is driving the moisture rather than guessing at it. Because this is a global field, the flow crosses the antimeridian instead of stopping at it, which over the Pacific is most of the picture.

Data from NOAA/NCEP via the AWS Open Data bucket noaa-gfs-bdp-pds. U.S. government work, in the public domain. Forecast Eagle is not affiliated with NOAA or the National Weather Service.