MRMS Renderer

MRMS Renderer is an open-source tool for retrieving, rendering, and visualizing NOAA Multi-Radar/Multi-Sensor (MRMS) radar data locally.

It turns recent NOAA ReflectivityAtLowestAltitude GRIB2 files into transparent PNG frames, writes a chronological frame manifest, and animates the sequence over an OpenStreetMap-based interactive map in the browser.

Requirements

• Python 3.11+
• ecCodes (with Python bindings installed via pip install eccodes or your package manager)
• NumPy and Pillow (installed automatically)

Setup

python3 -m venv .venv
source .venv/bin/activate
python -m pip install -e ".[dev]"

Usage

The CLI runs the full local workflow and never touches a hosted radar service — every byte is fetched from NOAA/NCEP.

Command	What it does
mrms-renderer discover	Lists up to 30 recent MRMS frames from the NOAA/NCEP index, newest first.
mrms-renderer frames	Full pipeline: download → decompress → decode (ecCodes) → render (NumPy/Pillow) → output/frames.json.
mrms-renderer view	Serves output/ and opens the browser viewer.
mrms-renderer demo	Runs frames then view: complete 30-frame pipeline + animated map.

Common options are --count N (default 30) and --output/-o PATH (default ./output).

The happy path

mrms-renderer demo

This downloads up to 30 recent reflectivity frames, decompresses and decodes them with ecCodes, renders transparent RGBA PNGs with NumPy and Pillow, writes the chronological manifest, and opens a local interactive map. Press play/pause, scrub the timeline, and change playback speed.

Output is written to the git-ignored output/ directory:

output/
  download/         *.grib2.gz
  decompressed/     *.grib2
  frames/           frame_YYYYMMDD-HHMMSS.png
  frames.json       chronological manifest
  index.html        local viewer (installed automatically)

Demo

Products

The v0.1 release is scoped to NOAA's ReflectivityAtLowestAltitude product. Frames are discovered from https://mrms.ncep.noaa.gov/2D/ReflectivityAtLowestAltitude/, which lists MRMS_ReflectivityAtLowestAltitude_00.50_YYYYMMDD-HHMMSS.grib2.gz files.

Reflectivity palette

The palette is centralized in src/mrms_renderer/palette.py and preserved unchanged from the prototype pipeline. dBZ values below 5.0 are fully transparent.

dBZ	RGBA
≥ 5.0	(80, 180, 255, 150)
≥ 10.0	(0, 220, 120, 180)
≥ 20.0	(0, 170, 0, 200)
≥ 30.0	(255, 200, 0, 220)
≥ 40.0	(255, 80, 0, 230)
≥ 50.0	(255, 0, 0, 240)

Any future palette or opacity change must be made in palette.py, covered by tests/test_color.py, and documented here.

Testing and linting

pytest
ruff check src tests

Tests cover the palette bands, frame discovery/parsing, grid decoding (including bounds derivation from GRIB metadata), rendering output, and manifest ordering.

Architecture

NOAA MRMS index
    ↓
discover  (mrms_renderer/discovery.py)
    ↓
download + decompress  (mrms_renderer/download.py)
    ↓
ecCodes decode  (mrms_renderer/decode.py)
    ↓
NumPy → RGBA → Pillow PNG  (mrms_renderer/render.py)
    ↓
frames.json manifest  (mrms_renderer/manifest.py)
    ↓
JavaScript viewer animation  (web/)

What this project is not

MRMS Renderer is not a hosted radar service, processed radar feed, commercial API, weather forecast service, or production framework. It includes none of Taylor Creative Development's private production infrastructure: no scheduling, cloud deployment, WeatherKit integration, CDN, databases, or authentication. Users retrieve and process NOAA data themselves.

Data attribution

Radar data is provided by NOAA through the Multi-Radar/Multi-Sensor (MRMS) system. Map tiles are © OpenStreetMap contributors (ODbL).

License

Apache License 2.0. See LICENSE.

MRMS Renderer is developed by Taylor Creative Development.