# 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

## References
- AWS S3: `s3://noaa-rrfs-pds/`
- NOAA RRFS: https://gsl.noaa.gov/focus-areas/unified_forecast_system/rrfs
- NOAA EMC RRFS: https://github.com/NOAA-EMC/rrfs-workflow