NEXRAD Mosaic Access

NEXRAD Mosaic Access retrieves existing NOAA/NCEP Multi-Radar/Multi-Sensor products for regional analysis. It distinguishes an official processed mosaic from a single NEXRAD volume and from a locally assembled composite. The workflow selects an exact product, domain, time, and file, then validates the downloaded bytes and decoded grid before promoting an artifact.

Product selection checks the name and version, radar-only or multisensor basis, gauge correction, accumulation period, time semantics, cadence, latency, spatial grid, units, packed representation, and quality values. QPE is accumulated precipitation; VIL represents vertically integrated liquid; VII represents vertically integrated ice; MESH concerns maximum expected hail size for its product interval. Those quantities must retain their documented meanings rather than be relabeled from their appearance.

The request records a UTC time or bounded historical interval, timestamp policy, geographic crop, output-grid policy, lookback, file-size limit, acceptable latency, and provenance requirements. Product descriptions and the live directory determine whether the requested domain and revision exist. A directory abbreviation or color image alone is insufficient for selection.

Use this skill to obtain a completed national or regional composite for mapping, analysis, or comparison without fetching every contributing radar volume. It supports requests involving QPE, VIL, VII, and MESH while preserving their product identities. Single-site sweeps and Level II or Level III access belong to nexrad-product-access. Custom multi-radar construction also sits outside this workflow. A broad mosaic can obscure individual-site vertical or velocity structure.

Provider products have coverage, quality, latency, and algorithmic limitations. They should not be labeled ground truth or direct observations. Missing coverage remains distinct from a physical zero, and gauge-corrected analyses remain distinct from radar-only estimates.

The public 2D archive is the starting access location:

https://mrms.ncep.noaa.gov/2D/

Retrospective work selects an exact timestamped compressed GRIB2 file. A latest convenience link is resolved to its actual identity, with retrieval time, valid time, final URL, redirect target, content length, and latency recorded separately. Downloads use request-owned temporary paths. Received size and provider checksums are checked where available; otherwise a local SHA-256 records byte identity. Decompression produces a separate temporary GRIB2 file rather than overwriting a shared cache.

A format-aware decoder checks product, reference and valid times, variables, units, missing values, projection, coordinate orientation, scan mode, dimensions, cell size, and packed calibration. Cropping follows native-grid validation unless a documented range request preserves the same bytes. The access record identifies provider, product, domain, requested time, selected timestamped URL, retrieval time, compressed size and hash, decoded-grid metadata, and whether latest was used. Unknown values are omitted or null where permitted.

The workflow uses official NOAA/NCEP resources and current NOAA/NSSL product documentation. Cache identities include product, domain, timestamped URL, and checksum. Partial files stay outside accepted cache entries; publication is atomic after decoder validation. Bounded retries, service limits, disk and memory checks, and request-owned cleanup protect retrieval reliability. Remote content is decoded with explicit libraries rather than executed, and records exclude credentials or signed query strings. Product and domain inputs are validated against path traversal. Preserve NOAA/NCEP attribution and applicable data-use terms.