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RAP model output

Available since v0.20.0 as noaa:rap. The Rapid Refresh is NOAA's hourly-cycled 13 km North American model, the parent HRRR nests inside. Its GRIB2 output lives in the anonymous noaa-rap-pds S3 bucket as rap.YYYYMMDD/rap.tHHz.<family>fNN.grib2, one whole file per run, forecast hour, and grid family, each beside a .grib2.idx sidecar. No AWS credentials or SDK are needed. The adapter shares its run selection with HRRR; read that page's explanation of runs, cycles, and valid times first.

Runs, cycles, and valid times

RAP runs every hour; cycle (required) names the run's UTC hour, 0 to 23. The query window selects runs by initialization time, inclusive, and spans at most one day; a bare date as both bounds is that whole day and selects its cycle run. A window containing no cycle initialization is rejected before any request.

Times are UTC

Timestamps without a timezone are treated as UTC, including queries built directly in Python; explicit offsets are converted to UTC. Both bounds are inclusive. A date alone as the end means the last instant of that UTC day, so a window from 2024-05-07 to 2024-05-07 is that whole day; give the end a time to stop earlier. See time and place.

forecast_hour (required) is an integer, a list, or a comma-separated string. The 03, 09, 15, and 21 UTC runs extend to 51 hours; every other run stops at 21. Hours outside the run's range are rejected before any request; an hour the archive lacks for an existing run is reported by name after the listing. Asset times record each file's valid time, initialization plus forecast hour.

File families and sizes

file Object name Content Size (2024-05-06 20Z, f00)
awp130 (default) awp130pgrbf 13 km CONUS Lambert grid, 451 × 337 points, pressure levels plus surface and derived fields: CAPE, CIN, helicity, reflectivity, 2 m and 10 m fields 18 MB
awp130b awp130bgrbf The remaining, less common fields on the same grid 41 MB
prs wrfprsf Pressure-level fields on the model's native rotated grid 228 MB
nat wrfnatf Native hybrid-level fields on the native grid 305 MB

The 20 km, 32 km, and 40 km families (awp252, awip32, awp236), the wrfmsl files, and the BUFR soundings are out of scope. Every file is a whole grid of hundreds of fields; the 13 km analysis holds 355 messages. variables, text, and geographic constraints are rejected because the server cannot subset the files. Check what a query will download before fetching:

uv run usdata fetch noaa:rap \
  --start 2024-05-06T20:00Z --end 2024-05-06T20:00Z \
  -p cycle=20 -p forecast_hour=0,1 --dry-run

Fetching selected messages

messages fetches only the GRIB2 messages you name, as byte ranges of the object, exactly as the HRRR guide describes. The sidecar is the key plus .idx. Selectors observed in the 2024-05-06 20Z awp130pgrb analysis:

Field messages
Surface-based CAPE and CIN CAPE:surface, CIN:surface
0–1 km and 0–3 km storm-relative helicity HLCY:1000-0 m above ground, HLCY:3000-0 m above ground
Mixed-layer CAPE (lowest 90 hPa) CAPE:90-0 mb above ground
Most-unstable CAPE (lowest 180 hPa) CAPE:180-0 mb above ground
Composite reflectivity REFC:entire atmosphere
2 m temperature and dewpoint TMP:2 m above ground, DPT:2 m above ground 
uv run usdata fetch noaa:rap \
  --start 2024-05-06T20:00Z --end 2024-05-06T20:00Z \
  -p cycle=20 -p forecast_hour=0 \
  -p messages="CAPE:surface,HLCY:3000-0 m above ground" --dry-run

Those two fields are about 80 KB of the 18 MB file. RAP packs the wind components of each level into one GRIB2 message holding two fields, which the index numbers 12.1 and 12.2 at one offset; naming either fetches the message whole, and the reader opens both. The fetched file is the messages concatenated, which is itself a valid GRIB2 file, and its lockfile entry pins the byte ranges and the object's ETag (ADR 0028).

Reading fields

The grib extra opens a file with FetchedAsset.open_grib2(select=...) as an xarray Dataset; a file fetched with messages is already a selection and opens without select. The awp130 grid is Lambert conformal, so the reader attaches two-dimensional latitude and longitude coordinates of shape (337, 451); longitudes use the 0–360 convention. See the HRRR guide for the select keys, which are the same ecCodes names, and the reader reference for the extra's platform support.

Archive coverage

The bucket's rap. day prefixes begin on 2021-02-22, whose 00 UTC run holds awp130pgrbf00; earlier day prefixes hold only NARRE files. Windows before that run are rejected before any request. The NODD registry entry documents public cloud access, and the RAP product page describes the model.

See the service research notes for dated upstream probes.

Metadata sources

Every value in the catalog entry's resolution, cadence, citation, terms, variables, and limits comes from one of these pages. A field the agency does not publish is left empty rather than estimated.

  • Resolution: the 451 × 337 Lambert grid at 13.545 km, read from a fetched awp130pgrb message with ecCodes on 2026-09-16, and the RAP product page.
  • Updates, citation, and terms: the NODD registry entry and the NOAA Open Data Dissemination statement it quotes.
  • Forecast-hour schedule: bounded listings of every cycle of rap.20240506/ on 2026-09-16, 22 files for most cycles and 52 for 03, 09, 15, and 21 UTC.
  • Variables: the messages table above. A file holds several hundred fields, so the entry lists only the ones this guide and the example use.
  • Longest query window: MAX_WINDOW in usdata.providers.noaa.hrrr, which this adapter shares through ModelRuns.
  • Latency is empty: NODD states no lag between a run's initialization and its appearance.

All NOAA datasets.

Reference

noaa:rap · Released · Included since usdata 0.20. RAP Model Output.

At a glance

  • Files: GRIB2
  • Selection: Files, whole or by named GRIB2 message, chosen by run initialization window, cycle hour, forecast hours, and file family
  • Required inputs: Both timestamps, cycle, and forecast_hour
  • Open locally: usdata[grib] · Reader guide
  • On usdata.dev: RAP model output, with a walkthrough

Parameters

Pass these as --param name=value to the CLI, as params: entries in a manifest, or as keyword arguments to build_query.

Parameter Meaning
cycle Required UTC initialization hour of the run, 0 to 23.
file File family: awp130 (default, 13 km CONUS pressure levels), awp130b (its secondary fields), prs (native-grid pressure levels), or nat (native levels).
forecast_hour Required forecast hour(s): an integer, list, or comma-separated string; 0 to 21, or 0 to 51 for the 03, 09, 15, and 21 UTC runs.
messages Optional GRIB2 messages to fetch instead of the whole file, spelled as the object's wgrib2 .idx sidecar spells them: 'SHORTNAME:level text', such as 'TMP:2 m above ground', with an optional ':step text'; one value, a list, or a comma-separated string. Short names are upper case and both fields match exactly.

Variables

Variable Units Meaning
cape J/kg Convective available potential energy, surface or a ground layer
cin J/kg Convective inhibition, surface or a ground layer
hlcy m2/s2 Storm-relative helicity over the 0-1 km and 0-3 km layers
refc dBZ Composite reflectivity
2t K 2 m temperature
2d K 2 m dewpoint temperature

Catalog facts

  • Availability: since 0.20
  • Domain: Weather models
  • Spatial resolution: 13 km Lambert conformal CONUS grid, 451 x 337 points, for the awp130 family
  • Temporal resolution: Hourly runs; forecast hours to 21, or to 51 from the 03, 09, 15, and 21 UTC runs
  • Updates: Hourly
  • Longest query window: 1 day
  • Terms of use: https://www.noaa.gov/information-technology/open-data-dissemination
  • Citation: NOAA Rapid Refresh (RAP) was accessed on [date] from https://registry.opendata.aws/noaa-rap
  • Catalog date range: 2021-02-22 to open-ended
  • Coverage varies by station, product, and date; the range above does not guarantee observations.
  • Upstream documentation
  • License: US Government Work (public domain)
  • Transport: s3
  • Adapter: usdata.providers.noaa.rap:Rap