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RRFS (Rapid Refresh Forecast System) Data Assessment

Overview

RRFS is NOAA's next-generation convection-allowing ensemble forecast system, intended to replace HRRR, RAP, NAM-NEST, and HREF. As of March 2026, RRFS is in operational evaluation — the ensemble post-processing products are publicly available on AWS S3, but the full deterministic model output with pressure-level fields is not yet publicly distributed.

Data Availability

AWS S3 Bucket: noaa-rrfs-pds

Two public prefixes with identical content:

  • rrfs_a/refs.YYYYMMDD/HH/enspost/ (primary)
  • rrfs_public/refs.YYYYMMDD/HH/enspost/ (mirror)

Run Schedule

  • 4x daily: 00Z, 06Z, 12Z, 18Z
  • Data available ~2 hours after init time
  • Recent data goes back about 10 days before being pruned

Available Products (CONUS)

Product File Pattern Contents Usefulness for Propagation
avrg refs.tHHz.avrg.fNN.conus.grib2 Ensemble mean Only APCP (precipitation accumulation). Not useful — missing temp, dewpoint, wind, pressure, refractivity profile
eas refs.tHHz.eas.fNN.conus.grib2 Exceedance probability APCP/ASNOW exceedance probabilities. Not useful for propagation scoring
ffri refs.tHHz.ffri.fNN.conus.grib2 Flash flood risk index PPFFG exceedance. Not useful
lpmm refs.tHHz.lpmm.fNN.conus.grib2 Ensemble mean (alternate) APCP only. Same limitation as avrg

Forecast Hours

  • f01 through f07 (1-7 hour forecasts)
  • ~1.5MB per file for ensemble mean CONUS

Grid

  • 3km CONUS domain (same as HRRR)
  • Lambert Conformal projection
  • GRIB2 format with standard .idx files

Key Finding: RRFS Public Data is NOT Sufficient for Propagation Scoring

The publicly available RRFS data on S3 contains only ensemble post-processing products — primarily precipitation statistics. It does NOT include:

  • Surface temperature (TMP:2m)
  • Dewpoint temperature (DPT:2m)
  • Surface pressure (PRES:surface)
  • Boundary layer height (HPBL)
  • Precipitable water (PWAT)
  • Wind speed/direction (UGRD/VGRD:10m)
  • Cloud cover (TCDC)
  • Pressure-level profiles (TMP/DPT/HGT at 1000-700mb) for refractivity gradient computation

These fields are essential for propagation scoring (all 9 factors). HRRR provides all of them.

RRFS vs HRRR Comparison

Feature HRRR RRFS (Public)
Resolution 3km 3km
Update frequency Hourly 4x daily (00/06/12/18Z)
Forecast range 18h (48h from 00/06/12/18Z) 7h (from public data)
Surface fields Full (TMP, DPT, PRES, wind, cloud, precip) APCP only
Pressure levels 8 standard levels (1000-700mb) Not available publicly
Refractivity profile Derivable from pressure-level T/Td/P Not possible
S3 bucket noaa-hrrr-bdp-pds noaa-rrfs-pds
Byte-range requests Yes (.idx files) Yes (.idx files)
Historical depth ~2 days on S3 ~10 days on S3

Recommendation

Continue using HRRR as the primary data source. RRFS public data is not yet suitable for propagation scoring due to missing atmospheric profile and surface fields.

Monitor for:

  1. NOAA making full RRFS deterministic output public (likely when RRFS becomes the operational replacement for HRRR)
  2. Additional fields being added to the ensemble post-processing products
  3. NOMADS distribution of full RRFS output (currently returns 403)

When RRFS full output becomes available, key advantages would be:

  • Ensemble spread information (confidence intervals on propagation scores)
  • Potentially improved boundary layer and moisture forecasts from the FV3 dynamic core
  • Longer forecast horizon for propagation prediction

Meteorologist Feedback (March 2026)

From a meteorologist familiar with Gulf region propagation:

Model choice validation:

  • HRRR is confirmed as the best short-term (0-48h) choice for low-level inversions and water vapor content. Higher vertical resolution in the boundary layer and tighter grid spacing give it the best handle on moisture — critical since humidity is our highest-weighted scoring factor (20%).
  • NAM should be avoided — substantially over-estimates low-level water content, especially in the western Gulf region. Over-does fog and water vapor discontinuities. Would produce false-positive ducting predictions in exactly the areas where ducting matters most.
  • GFS is better for days 2-5 forecasts, with a more pessimistic (and more correct) stance on moisture. Worth considering if we add a multi-day propagation forecast view.

RRFS transition notes:

  • HRRR will be operationally replaced by RRFS in the next few years
  • The meteorologist expects RRFS files may use netCDF format (current experimental output on S3 is GRIB2 — the full operational output format may differ)
  • The transition should be "fairly straightforward" — the scoring algorithm itself won't change, only the data ingestion layer
  • RRFS is already available experimentally but (as documented above) the public output lacks the fields we need

Implications for our architecture:

  • Keep HRRR as primary source — validated by domain expert
  • Don't use NAM for anything moisture-related
  • The Propagation.Scorer module is data-source-agnostic by design — when RRFS becomes available, only the fetch/extraction layer needs to change
  • If we add forecast beyond 48h, consider GFS as a supplementary source for days 2-5

References