BowEcho

A fast, free, native NEXRAD Level II radar viewer.
Live super-resolution base data, dealiased velocity, dual-pol, derived severe-weather products, synced multi-pane, and vertical cross-sections — in a single small download.

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BowEcho decodes raw NEXRAD Level II data straight from the public AWS archive and live chunk feed (no account, no API key) and renders it with a fast CPU rasterizer that preserves the native super-resolution pixel pattern. It is built in Rust for speed: products switch instantly, panning stays fluid, and first pixels from a fresh volume arrive in well under a second on typical connections.

Download

Grab the latest build from the Releases page:

Platform	File
Windows x64	bowecho-windows-x64.exe (or .zip with licenses bundled)
Windows x64, CPU from ~2015+	bowecho-windows-x64-v3.exe (AVX2: ~20-30% faster radar rendering)
Windows ARM64	bowecho-windows-arm64.exe
macOS Apple Silicon	bowecho-macos-apple-silicon.zip
macOS Intel	bowecho-macos-intel.zip
Linux x64	bowecho-linux-x64
Linux ARM64	bowecho-linux-arm64

Windows: download the .exe and run it - that's it. The exe is fully self-contained (no installer, no runtime dependencies). Windows builds are not yet code-signed, so SmartScreen may show "Windows protected your PC" the first time: click More info -> Run anyway.

Antivirus false positives. Windows Defender's machine-learning heuristics sometimes flag new, unsigned Rust executables with names like Trojan:Script/Sabsik.fl.A!ml or Wacatac.B!ml — the !ml suffix means "ML guess", not a matched virus signature, and it's a well-known false positive for freshly compiled open-source binaries. Every BowEcho release is built by GitHub Actions directly from the tagged source in this repository (the full build log is public under the Actions tab), and each asset ships with a .sha256 checksum so you can verify your download is byte-identical to what CI produced: Get-FileHash bowecho-windows-x64.exe (PowerShell) and compare. If Defender quarantines it, restore + add an exclusion, or report the false positive to Microsoft at https://www.microsoft.com/en-us/wdsi/filesubmission — developer submissions of !ml detections are typically cleared within days. You can always audit and build from source instead (see below).

macOS: unzip and open BowEcho.app. Release apps are signed and notarized when the repository's Apple Developer ID secrets are available. If Gatekeeper still shows a first-run warning after a manual download, right-click the app and choose Open once (or run xattr -d com.apple.quarantine BowEcho.app in Terminal).

Linux: the download is the binary itself - chmod +x bowecho-linux-x64 && ./bowecho-linux-x64 (needs X11/Wayland + OpenGL, standard on desktops).

Trust and verification

BowEcho releases are produced by GitHub Actions from the exact tagged source in this repository. Each downloadable asset is published with a .sha256 file so users can verify that a local download matches the CI-built artifact.

Get-FileHash .\bowecho-windows-x64.exe -Algorithm SHA256

Compare the hash with the matching .sha256 file on the release page. For signing status, false-positive guidance, and responsible disclosure, see docs/SIGNING.md and SECURITY.md.

The docs/ tree also preserves curated AI-assisted engineering records: design rationale, literature checks, adversarial verification notes, and handoffs. See docs/ai-assisted-engineering-process.md for what is intentionally kept public and docs/public-docs-hygiene.md for the publication checklist.

Quick start (storm mode)

1. Launch BowEcho. Pick a radar site from the sidebar (or right-click any site marker on the map) — the latest volume loads automatically.
2. The LIVE chip means auto-refresh is on; new volumes stream in as the radar scans. ARCHIVE/STALE chips tell you when you're not looking at current data.
3. Arrow keys: ←/→ cycle products, ↑/↓ change tilt. Scroll to zoom, drag to pan.
4. Quad view: sidebar → Layout 4 for synced REF / VEL / CC / ZDR. Click any pane to focus it (blue border), then the sidebar or arrow keys retune that pane — its own product and a pinned tilt. The main (top-left) pane drives everything that isn't pinned.
5. Inspector: hover for the data card (value, range/azimuth, beam height, Vrot). Shift+click pins it to a spot — it sticks through pan/zoom and updates every volume. Velocity products draw an inbound/outbound arrow.
6. Cross-section: tick Cross-section in the sidebar, click two points, and a vertical slice (RHI) renders below the map — reflectivity, or dealiased velocity when a velocity product is selected.
7. Declutter: Hide below applies a render-time threshold (on velocity it clamps |v|, so couplets pop while the noise around zero disappears).

Products

Base / dual-pol: Reflectivity, Velocity (with region-based dealiasing), Storm-relative velocity, Spectrum Width, ZDR, CC (ρhv), PHI, KDP — each with a purpose-built color table (plus GR2-style presets, user-imported .pal tables, and a colorblind-safe velocity option).

Derived: Composite Reflectivity, Echo Tops, VIL, VIL Density, Azimuthal Shear (LLSD rotation), Radial Divergence — computed volume-locally in tens of milliseconds and selectable like any product.

Storm analysis: NSSL-style mesocyclone/TVS detection (Stumpf et al. 1998; Mitchell et al. 1998) with time-association (CPLT → MESO), SCIT storm cell tracks with motion extrapolation (Johnson et al. 1998), maximum expected hail size (Witt et al. 1998), live draggable cross-sections, and GRLevelX placefiles (icon sheets, Object blocks, auto-refresh).

Velocity dealiasing offers two engines: region-based unfolding (Jing & Wiener 1993; Feldmann et al. 2020) — validated on real derecho data at 99% residual-fold reduction — and an experimental tilt-cascade engine that branch-checks each tilt against the wind fit from the tilt above (Browning & Wexler 1968; Louf et al. 2020). Raw-velocity mode always carries a "folds possible" tag plus near-Nyquist warnings in the inspector. The algorithms and their references are documented in docs/products-guide.md.

Display: 1/2/4-pane synced grids with per-pane products and honest per-pane readouts, optional GR2-style smoothing (zero panning cost), and an azimuthal-equidistant projection so range and azimuth are true at every latitude.

Why it's fast

• Native Rust, lean CPU rasterizer, full quality at every zoom.
• Parallel block-bzip decompression pipelined with parsing — first pixels in tens of milliseconds once data arrives.
• One bounded render worker serves every pane (no thread oversubscription), with keyed moment/sample caches shared across panes.
• View-pure geometry (basemap projection, hazard tessellation) is cached per view, so idle repaints cost almost nothing.
• Honest stage timings in the status bar: lookup, fetch, decode, render, texture, cache.

Data & hazards

• NEXRAD Level II from the public unidata-nexrad-level2 S3 archive and the real-time chunk feed. No keys, no accounts, no middleman servers.
• Live NWS warnings/advisories and SPC mesoscale discussions overlay as clickable polygons with product-aware fills.
• Multi-radar overlays: load neighboring sites on the same map with independent refresh, opacity, and visibility.
• Mobile/research radars: open DOW, COW, and RaXPol data natively — DORADE sweepfiles and deployment zips decode straight to the map (transition-ray filtering, staggered-PRT Nyquist, CFAC corrections), and a GR2A-style polling URL follows field feeds live. When a FARM facility radar is deployed and plotting, BowEcho lights a LIVE chip and plays the quicklook loop (quicklooks courtesy of the FARM facility).

Build from source

git clone https://github.com/FahrenheitResearch/bowecho
cd bowecho
cargo run --release -p app_ui --bin bowecho

Rust stable (edition 2024). Linux needs pkg-config libgl1-mesa-dev libx11-dev libxi-dev libxkbcommon-dev.

Disclaimer

BowEcho is an enthusiast/analyst tool, not a warning service. Never use it as a substitute for official National Weather Service warnings and guidance. During severe weather, follow your local NWS office and emergency management.

Credits

Data sources

• NOAA / National Weather Service — NEXRAD Level II radar, MRMS, GOES imagery and GLM lightning, and SPC/WPC forecast products.
• EUMETNET OPERA and the participating national meteorological services — European weather radar via the OPERA Development Radar Data (ORD) service, including Spain's AEMET radar network (opened through ORD in June 2026). ORD radar data is licensed CC BY 4.0; BowEcho displays it with attribution to OPERA and the originating national services.
• National open-data radar feeds: SMHI (Sweden), FMI (Finland), DWD (Germany), DMI (Denmark), CHMI (Czechia), SHMÚ (Slovakia), GeoSphere Austria, the Estonian Environment Agency, Romania's ANM (Data: Administrația Națională de Meteorologie (ANM) România), JMA (Japan — radar and Himawari satellite), Italy's Dipartimento della Protezione Civile with the ARPA Piemonte and ARPA Lombardia regional services, Taiwan's Central Weather Administration, and Australia's Bureau of Meteorology (via NCI).
• Crowd-sourced weather reports from mPING (NOAA National Severe Storms Laboratory / University of Oklahoma). Convective outlooks from ESTOFEX.

Contributed work

• Annotation graphics vocabulary contributed by GBW Overlay — grayskieswx (YouTube). The map annotation tools' front glyphs, hatch fills, warning-polygon styling, and icon designs reimplement his renderer's geometry in Rust, shared by the author for this purpose.
• Research-radar color tables ("research" badge in the pickers) from GURT V3 — the Graphic Utility Radar Toolkit by ambient330 (Graphic-Utility-Radar-Toolkit-V3, MIT license), used with appreciation. The GURT reflectivity, velocity, spectrum width, CC, ZDR, and KDP ramps are ported value-for-value, tuned for DOW/COW mobile-radar (X-band) work.

License

Dual-licensed under MIT or Apache-2.0, at your option.