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NEXRAD severe weather radar — Asheville during Hurricane Helene

Find Level-II base radar volumes and Level-III processed products for a specific location and event window.

What this teaches

  • Discovering NEXRAD radar stations by location (bbox)
  • Reading the per-station coverage polygon (~230 km radar range)
  • The asset structure for NEXRAD on Google Cloud Storage
  • Combining Level-II (raw volumes) with Level-III (processed products)

Sources used: NEXRAD_L2, NEXRAD

Prompt

Hurricane Helene caused catastrophic flooding in Asheville, NC in late
September 2024. Show me the nearest NEXRAD radar stations to Asheville
and how to access their archived data for that storm window.

Transcript

1. Find radar stations near Asheville

search_datasets(
  collections = "NEXRAD_L2",
  bbox = "-83,35,-82,36",
  limit = 5
)

Real results — three stations cover Asheville's airspace:

Station ID Title Location Elevation
nexrad_l2_kmrx KMRX — Knoxville Hamblen, TN 437 m
nexrad_l2_kjkl KJKL — Jackson Breathitt, KY 445 m
nexrad_l2_kgsp KGSP — Greer Spartanburg, SC 326 m

Each station's bbox is the ~230 km radar range polygon. Variables (Level II, dual-pol since 2013): reflectivity, radial velocity, spectrum width, differential reflectivity (ZDR), correlation coefficient (CC, RhoHV), differential phase (PhiDP).

2. Get one station's asset URLs

get_item(collection = "NEXRAD_L2", item_id = "nexrad_l2_kgsp")

Asset keys: gcs_browse (Google Cloud Storage console), gcs_data (raw archive bucket path), ncei_viewer (NCEI's web viewer).

The GCS path is gs://gcp-public-data-nexrad-l2/<YYYY>/<MM>/<DD>/<STATION>/ — for KGSP on Sep 27 2024 that's gs://gcp-public-data-nexrad-l2/2024/09/27/KGSP/. Files are gzipped Level-II Archive II files, one per volume scan (~5 minutes).

Result the agent gave

"Six NEXRAD Level II stations match the Asheville bbox; the three with coverage polygons that intersect Asheville (~35.6°N, 82.6°W) are:

  • nexrad_l2_kgsp — KGSP (Greer, Spartanburg County, SC). Elevation 326 m. Bbox -84.74°W to -79.70°W, 32.82°N to 36.95°N — Asheville is well within range to the NW.
  • nexrad_l2_kmrx — KMRX (Knoxville, Hamblen County, TN). Elevation 437 m. Bbox -85.96°W to -80.84°W, 34.10°N to 38.23°N — covers Asheville from the west.
  • nexrad_l2_kjkl — KJKL (Jackson, Breathitt County, KY). Elevation 445 m. Bbox -85.92°W to -80.71°W, 35.52°N to 39.66°N — covers Asheville from the NNW.

Each station is operational since 1991 and provides the full dual-pol Level II suite: reflectivity, radial velocity, spectrum width, ZDR, correlation coefficient (RhoHV), differential phase (PhiDP).

Asset keys: gcs_browse (Google Cloud Storage console), gcs_data (raw archive bucket), ncei_viewer (NCEI web viewer).

GCS path layout: gs://gcp-public-data-nexrad-l2/<YYYY>/<MM>/<DD>/<STATION>/ — files are gzipped Archive II volume scans, ~5 min cadence per file.

For Hurricane Helene's Asheville-area window (Sep 26–27, 2024): - KGSP, Sep 27: gs://gcp-public-data-nexrad-l2/2024/09/27/KGSP/ - KMRX, Sep 27: gs://gcp-public-data-nexrad-l2/2024/09/27/KMRX/ - KJKL, Sep 27: gs://gcp-public-data-nexrad-l2/2024/09/27/KJKL/

Open the .gz files with Py-ART (pyart.io.read_nexrad_archive(...)) or GR2Analyst. AQUAVIEW is the discovery layer; storm-relative interpretation requires the actual radar volumes."

Variations

  • Different storm: change the datetime filter window. Hurricane Ian 2022 landfall day: 2022-09-28T00:00:00Z/2022-09-29T00:00:00Z.
  • Tornado event: bbox a Plains state and pull KOUN, KFWS, KTLX volumes for the affected day.
  • Level III only: switch NEXRAD_L2 → NEXRAD for processed products (precipitation accumulation, storm-relative velocity, hail index, etc.).
  • Composite: aggregate by geometry_geotile_grid_frequency to map radar coverage gaps.