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NEXRAD Level III products

Available since v0.15 as noaa:nexrad-level3. The public unidata-nexrad-level3 bucket holds derived single-radar products as flat keys SITE_PRODUCT_YYYY_MM_DD_HH_MM_SS, one object per product per volume scan. The site is the radar's ICAO id without its first letter (KTLX is TLX, PABC is ABC); the adapter maps ids for you, so queries still use KTLX. The bucket begins on 2020-03-30 and keeps everything since. Provide both timestamps, a radar or geographic query, and the products you want:

usdata fetch noaa:nexrad-level3 -p site=KTLX -p products=N0B,NMD \
  --start 2024-05-06T20:00Z --end 2024-05-06T20:30Z --dry-run

Site selection follows Level II: site or sites, radars inside a bounding rectangle, or nearest. UTC bounds include both endpoints and span at most 31 days per query. A window that starts before 2020-03-30 is rejected before any request and names the NCEI archive, which this adapter does not reach.

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.

Products

products is required, case-insensitive, and validated against the codes below; an unknown code is rejected by name before any request. Each code selects distinct whole files; it is a parameter rather than a variables filter, so the adapter rejects variables and the entry declares variable_subset: false. Ask in an issue to extend the list.

For the moment products the digit or letter after N selects the elevation slot: 0 is the lowest tilt, and 1, 2, 3, A, and B are higher slots whose exact angles depend on the volume coverage pattern in use.

Code Product Typical size (KTLX, 2026-09)
N?B Base reflectivity, super-resolution (since 2022-02-18) 240 kB at N0B, smaller aloft
N?G Base velocity, super-resolution (since 2022-02-18) 190 kB at N0G
N?Q Base reflectivity, 256 levels (retired 2022-09-08; use B) 37 kB
N?U Base velocity, 256 levels (retired 2022-09-08; use G) 114 kB
N?S Storm-relative mean radial velocity 27 kB
N?C Correlation coefficient 157 kB
N?X Differential reflectivity 144 kB
N?K Specific differential phase 11 kB
N?H Hydrometeor classification 15 kB
NCR Composite reflectivity 37 kB
EET Enhanced echo tops 1.5 kB
DVL Digital vertically integrated liquid 7 kB
NMD Mesocyclone detection 150 B when empty, 2 kB with detections
NST Storm tracking information 10 kB
NTV Tornado vortex signature (retired 2022-05-24) 2 kB
NVW VAD wind profile 9 kB
DHR Digital hybrid-scan reflectivity varies
HHC Hybrid hydrometeor classification varies
DAA Digital one-hour precipitation accumulation 224 B when dry
DTA Digital storm-total precipitation accumulation 1.8 kB
DSP Digital storm-total precipitation varies
OHA One-hour precipitation accumulation varies

Retired codes remain in the list so 2020–2022 requests can still name them; requesting one for a later date lists nothing. Sizes are medians from one clear-air day and grow with weather. A radar produces roughly 120 to 390 files per product per day depending on its scan strategy, so a day of one product is one listing request and up to a few hundred small downloads.

The bucket holds what the Unidata feed captured, and an empty or short listing inside the archive period is not an error; the adapter does not fill it from NCEI. A short listing is not always a feed gap. On 2024-05-06 KTLX's echo-top files run from 20:34 UTC, while its mesocyclone and storm-track files begin at 20:42:46, the scan whose header shows the radar leaving clear-air VCP 35 for precipitation VCP 212 (walkthrough). Check the volume coverage pattern before reading missing files as lost ones.

No reader

Level III is a separate binary format from Level II, and this release ships no reader for it. FetchedAsset.open() raises UnsupportedFormat naming fetched.path. Decode the cached file with Py-ART or another Level III decoder:

import pyart

radar = pyart.io.read_nexrad_level3(item.path)

Provenance, checksums, lockfiles, and restoration work as for every other dataset; only decoding is external.

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.

  • Temporal resolution and updates: the file counts and feed gaps documented above, measured from the bucket; the bucket holds what the Unidata feed captured.
  • Citation and terms: the NODD registry entry and the NOAA Open Data Dissemination statement it quotes.
  • Variables: the product-code table above, which is the exact list this adapter accepts.
  • Longest query window: MAX_WINDOW in usdata.providers.noaa.nexrad_level3.
  • Spatial resolution and latency are empty: no upstream page states a per-product grid spacing or a lag for this bucket.

All NOAA datasets.

Reference

noaa:nexrad-level3 · Released · Included since usdata 0.15. NEXRAD Level III Products.

At a glance

  • Files: NEXRAD Level III (no reader)
  • Selection: Whole product files by site, product code, and inclusive UTC scan time since 2020-03-30
  • Required inputs: Both timestamps; product codes; radar IDs or a geographic query
  • Open locally: Local files; no bundled reader for this format
  • On usdata.dev: NEXRAD derived radar products, 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
nearest Take the N radars nearest the query centre instead of naming sites.
products Required Level III product codes, comma-separated or a list, for example N0B,NMD.
site One radar ICAO id, for example KTLX.
sites Several radar ICAO ids, comma-separated or a list.

Variables

Variable Units Meaning
N?B — Base reflectivity, super-resolution (since 2022-02-18)
N?G — Base velocity, super-resolution (since 2022-02-18)
N?Q — Base reflectivity, 256 levels (retired 2022-09-08)
N?U — Base velocity, 256 levels (retired 2022-09-08)
N?S — Storm-relative mean radial velocity
N?C — Correlation coefficient
N?X — Differential reflectivity
N?K — Specific differential phase
N?H — Hydrometeor classification
NCR — Composite reflectivity
EET — Enhanced echo tops
DVL — Digital vertically integrated liquid
NMD — Mesocyclone detection
NST — Storm tracking information
NTV — Tornado vortex signature (retired 2022-05-24)
NVW — VAD wind profile
DHR — Digital hybrid-scan reflectivity
HHC — Hybrid hydrometeor classification
DAA — Digital one-hour precipitation accumulation
DTA — Digital storm-total precipitation accumulation
DSP — Digital storm-total precipitation
OHA — One-hour precipitation accumulation

Catalog facts

  • Availability: since 0.15
  • Domain: Weather radar
  • Temporal resolution: One file per product per volume scan; roughly 120 to 390 per product per day
  • Updates: Files appear as the Unidata feed captures them, and coverage has gaps
  • Longest query window: 31 days
  • Terms of use: https://www.noaa.gov/information-technology/open-data-dissemination
  • Citation: NEXRAD on AWS was accessed on [date] from https://registry.opendata.aws/noaa-nexrad
  • Geographic bounds (WGS84): west -180°, south 15°, east -60°, north 72°
  • Catalog date range: 2020-03-30 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.nexrad_level3:NexradLevel3