Why?
The 12 km NAM ran for over two decades, and forecasters were sad to see it go. NOAA retired the NAM on 3 November 2026.
FrankenNAM brings the NAM back to life — in a modified, lower-cost form. It uses the NAM’s own physics, which is a US-government work and was public, running on ordinary CPUs on AWS. By skipping the data assimilation, it costs only a few dollars a run, and we explain how to run it yourself. We run it occasionally, not on a schedule: notable events, run on demand and added as cases.
WOOF-NAM, from Recast Systems, rewrites the NAM for GPUs and runs it daily; its grids are currently free and available here. Differences between FrankenNAM and WOOF-NAM are described here.
How close is it? Over five hindcast cases, at 24 h FrankenNAM is about half as far from the archived NAM as the GFS is: 1.0 K against 2.1 K in 2 m temperature, 0.9 against 1.9 hPa in sea-level pressure (RMS difference). Near the surface it runs drier than the NAM, by about 0.9 K in 2 m dew point over the first day; the cause is not yet found. Details on the Validation page.
Validation cases
CAD ice storm
23 Jan 2026 12Z run, Georgia and the Carolinas, f39
- Freezing rain and sleet cover 295k km², the same as the NAM’s. The sub-freezing wedge covers 393k km² against the NAM’s 397k.
Snowcrete
5 Jan 2025 12Z run, Washington DC, snow to sleet, f21
- Snow, sleet and freezing rain cover 130k, 66k and 16k km² against the NAM’s 153k, 41k and 45k: the same pattern, with more sleet and less freezing rain. By f36 both are all snow.
Gulf Coast snow
21 Jan 2025 00Z run, f30
- The same snow band as the NAM’s, with a larger area: 24 h snow above 5 cm covers 255k km² against the NAM’s 201k at f30 (27 % larger), and 163k against 116k at f42 (40 % larger).
- Heaviest 24 h snow: 32.2 cm against 23.6 cm at f30, 20.9 against 23.6 cm at f42.
PNW bomb cyclone
19 Nov 2024 12Z run, with an atmospheric river, f12
- The low is 946.9 hPa at f12 and 954.1 at f24, against the NAM’s 941.0 and 950.3: about 6 and 4 hPa weaker. The track is within 0.2°; peak 10 m wind is 29.2 against 29.7 m/s.
Example maps
Pick a field, region and hour, or press play.