ABOUT FORECAST EAGLE

What this is, where the data comes from, how it is made.

Forecast Eagle presents North American weather using data produced by U.S. government agencies — the National Oceanic and Atmospheric Administration, the National Weather Service, and the National Centers for Environmental Prediction. All of it is public, taxpayer-funded, and free. The problem has never been the data; it has been the presentation.

Why build this

NOAA runs some of the most sophisticated numerical weather prediction on Earth and then publishes much of it as fixed-size GIFs and static charts that have barely changed in twenty years. Meanwhile the raw GRIB2 files sit on public servers, perfectly usable, largely unexamined outside the profession.

This site takes those files and renders them honestly: real colour scales, real resolution, real timestamps. It is aimed at the whole range of people who care — the storm chaser, the pilot, the farmer, the emergency manager, and the person who simply wants to know whether the cookout is going to get rained on.

The RRFS

The Rapid Refresh Forecast System is NOAA's next-generation convection-allowing model. It runs hourly at 3 km over the continental United States, with companion domains for Alaska, Hawaii and Puerto Rico, and it is currently running in parallel with the operational HRRR it is intended to succeed. That parallel period is unusual and worth watching: it is a rare public look at a national forecast model being shaken out in real time.

Because it is experimental, RRFS output here is a research and situational-awareness tool. For watches, warnings and advisories the National Weather Service is always the authority.

How the imagery is made

Each forecast hour of RRFS CONUS output is a GRIB2 file of roughly 385 MB, and NOMADS publishes no index sidecar for RRFS — so the usual trick of reading an index and fetching only the messages you want is unavailable. Rather than download tens of gigabytes per cycle, Forecast Eagle exploits the file's fixed field ordering: every variable shown here lives in the first ~45% of the file, so a single HTTP range request retrieves a prefix, which is then trimmed to its last complete GRIB message and decoded locally.

Fields are decoded with wgrib2, warped from the model's native Lambert Conformal grid onto Web Mercator, colour-mapped against fixed absolute scales, and published as palettised PNGs. The browser then draws them on a plain canvas — there is no mapping framework on this site, because the rasters are already axis-aligned to the projection the map is drawn in.

Model: NOAA/NCEP RRFS v1 (parallel)
Domain: CONUS, 1799 × 1059 Lambert Conformal
Resolution: 3 km, hourly cycles
Source: NCEP NOMADS
Update: Hourly, roughly 40 minutes past the hour
Boundaries: U.S. Census Bureau cartographic files

Principles

Absolute colour scales. Ramps never re-fit themselves per frame, so an animation shows real intensity changes rather than a palette rescaling.
No invented resolution. Model grids are drawn at their true spacing; zooming in reveals real 3 km cells instead of a smooth interpolation the model never produced.
Traceability. Every field states its model, cycle and valid time, so any number can be traced back to the NOAA file it came from.
No surveillance. No trackers, no analytics, no cookies, no account. Static files over HTTPS.

weather.city is the companion site, covering places — cities, counties, airports, climate records and normals. Forecast Eagle covers the models and the national datasets behind them.

Credits and disclaimer