ArWen

Explore weather, create regional forecasts, and run them on your own hardware.

ArWen combines a native desktop application, a terminal workspace, and a CUDA-based atmospheric modeling engine. Use the desktop to inspect weather maps, choose a forecast area or cyclone, review the setup, and follow your results. Run the model on a local NVIDIA GPU or a Linux computer connected over SSH.

The Linux desktop displaying a real ERA5 field. Windows uses the same interface.

Get ArWen

Download	Requirements
Windows desktop: GUI and TUI	x86-64 Windows; compatible NVIDIA GPU and driver; internet for first setup
Linux desktop: GUI and TUI	x86-64 Linux, glibc 2.39 or newer, such as Ubuntu 24.04; Python 3.11 or newer; X11 or Wayland with working OpenGL
Integration kit	Developer guide, CLI/plan examples, catalogs, and client design notes

The desktop archives contain the applications, native map library and map assets. Windows includes a graphical setup launcher that downloads a private Python and CUDA runtime on first use. Linux uses the manual setup below. No Rust or C++ compiler is needed for these binary packages.

The Python package is named gpuwm. Its Windows and Linux platform wheels include the engine, native processing tools, and TUI. The desktop GUI is the separate download above. Check release notes and checksums for the exact artifacts and qualification records.

Install the desktop for forecasts on your PC

Windows

1. Download the Windows desktop ZIP and extract it into its own folder.
2. Open ArWen.exe. The setup window installs the matching engine and GPU dependencies, shows progress, and checks the local GPU.
3. When the workspace opens, choose Create forecast, draw an area, review the configuration, and run it on Local computer.

Python and the user-space CUDA components are managed by the application. A compatible NVIDIA driver must already be installed. Keep the resources folder beside ArWen.exe. Setup errors remain visible with retry and repair controls; setup does not require terminal commands.

First setup also prepares the physics tables and global geography needed for regional forecasts. Allow several gigabytes of downloads and at least 25 GB of free disk space, plus space for weather inputs and forecast output.

Linux

python3 -m venv ~/.local/share/arwen/venvs/2.7.5
~/.local/share/arwen/venvs/2.7.5/bin/python -m pip install 'gpuwm[all-cu12]==2.7.5'
~/.local/share/arwen/venvs/2.7.5/bin/python -m gpuwm.cli fetch-tables
~/.local/share/arwen/venvs/2.7.5/bin/python -m gpuwm.cli doctor

Extract the complete Linux tarball. From its application folder:

./Start\ ArWen.sh --python ~/.local/share/arwen/venvs/2.7.5/bin/python

If your distribution does not include Python's venv module, install its venv package first; Ubuntu provides python3-venv.

The Linux launchers open the connected GUI and TUI. Use Start ArWen Terminal.sh for the terminal alone. After activating a Python environment, gpuwm tui also opens the terminal.

Settings and run caches live outside the application folder. Keep the application files and notices together when moving or updating the desktop.

GPU requirements and forecast data

The normal desktop installation above already includes the GPU dependencies. Local forecasting requires a compatible NVIDIA GPU and driver. A card's VRAM capacity alone does not establish driver or CUDA compatibility.

For a manual Python installation on a supported CUDA 13 GPU and driver, replace all-cu12 with all-cu13 in the installation command. Install only one CuPy/CUDA major in each environment. A driver reporting CUDA 13 support can also run CUDA 12 applications; that display does not require switching a working CUDA 12 installation. See NVIDIA's compatibility guidance.

gpuwm doctor reports each remedy as a command or a # comment explaining the manual step.

The GPU extra installs CuPy and the required user-space NVIDIA CUDA components through their dependency packages. It does not install Python or the NVIDIA device driver. Install one CuPy/CUDA major per environment. See the CuPy installation guide and ArWen hardware guidance.

Most scientific lookup data arrives with the automatically installed gpuwm-data package. gpuwm fetch-tables obtains and hash-checks two additional Thompson tables, about 314 MiB combined. Geography and forecast inputs are separate: configure an existing geography installation or use gpuwm fetch-geog. ERA5 requires the user's CDS configuration and dataset access. Remote operation requires an SSH client and a configured, reachable forecast computer.

Local forecast integration runs on CUDA; it has no CPU fallback. The desktop, terminal, native weather processing, and remote-control workflows can run on a computer without a local CUDA installation.

Only an intentionally viewer-only or remote-control installation should use gpuwm[render]==2.7.5 without a GPU extra. It cannot execute local forecasts.

Work with weather

• Explore: choose a supported source, field, area, and valid time; load a weather map and play available UTC frames.
• Create forecast: start from an area, an Explore map, a saved configuration, or a cyclone setup. Choose the forecast computer and inputs, review the resolved physics and memory requirements, then launch.
• My forecasts: return to active or saved runs, inspect domains and output times, view native fields and plots, and play the forecast history.
• Terminal and CLI: use gpuwm tui for an interactive workspace or the command interfaces for scripts and automation.

Forecast and cyclone setup use the shared preparation source catalog, with geographic coverage, available times and required fields determined by the source. The installed source catalog is available through gpuwm sources --json. Forecast-input support and Explore preview support are separate; some registered forcing sources do not yet have an Explore preview route.

Local data assimilation is experimental and hidden in the ordinary desktop. Advanced users can enable its entry point with gpuwm tui --enable-local-da. A local DA run scores its own forecast against the MRMS composite, and gpuwm local-da --continuous cycles a regional analysis window after window, with a durable stop and a resume. A score is a measurement of that run: it masks a 9 km rim, scores one member, and is not a skill claim for the release. Continuous cycling is qualified as a door and a state machine; analysis quality is not part of that qualification.

Offline downscaling can retain the parent's physics or change the child's microphysics scheme. A child of a different scheme is converted by the same transition the live nest edge runs, on the parent archive before interpolation, between any two of Kessler, WSM6, WDM6, Thompson, aerosol-aware Thompson, Morrison, Milbrandt-Yau, NSSL and P3; WDM6 archives are read like every other scheme's. The one edge without a contract is a microphysics-off parent or child, which the review refuses by name.

For a configuration already prepared for your computer and inputs:

gpuwm go forecast.toml --dry-run
gpuwm go forecast.toml

The first command reviews the route; the second executes it. See the CLI manual and TUI manual for the complete workflows.

Integrate ArWen into another application

The integration guide and downloadable kit describe the CLI, run-plan documents, catalogs, and companion bridge boundaries. The kit contains an example subprocess client and tests. It is a documented integration surface, not a separate simulation engine or a replacement for runtime validation.

Use the installed catalogs and validated plans when building another interface. Preserve request identity, selected source/time/domain, cancellation, and the distinction between a preview and an executing forecast.

Science, compatibility, and current limits

ArWen independently implements a WRF-ARW-class regional atmospheric model and WRF-derived physics on the GPU. Its numerical comparisons and qualification apply to documented configurations and test cases. They do not establish universal equivalence with WRF or validate every combination of physics, input dataset, and hardware. Read the verification record, physics documentation, and 2.7 changes.

2.7.5 adds ICON global forcing, a score beside every local DA forecast, continuous local cycling, offline microphysics transitions for every ported scheme, ensemble products in the shared product tree, cyclone quick forecasts that start at any lead and grow their following nest to a memory budget, and remote retrieval of a run's whole output set, and it makes MYNN, the shortwave chain and the RUC land surface cheaper on the same card. What this release qualifies is its artifact and startup checks, a short GPU forecast, and the scoped component evidence the verification records name. Outside that qualification: general forecast skill, whole-model parity, and the quality of a forecast initialised from ICON global. Two gaps are known and named rather than qualified: the standalone rw-wps bundle does not carry the gdt101_remap remapper, which gpuwm doctor reports, and the desktop weather map cannot draw ICON global fields, which does not affect the forecast.

• Checkpoints: 2.7 writes format 6. Format-5 checkpoints from older releases and previews are not compatible. Finish those runs with the version that created them, or start again from the original configuration and inputs.
• Noah-MP memory basis: sf_surface_physics = 4 is priced from the per-thread frames its kernels compile to, which are readings of a compile platform (target architecture and NVRTC build). The NVRTC build is set by the cuda-toolkit release the package's [ctk] extra resolves to when pip runs, not by the machine. The desktop runtime is a CUDA-12 install. This release carries readings on both CUDA majors: sm_120 and sm_86 on NVRTC 12.9.86, the build a CUDA-12 install resolves (gpu-cu12, gpu, all, and the desktop runtime), and sm_120 on the two builds the gpu-cu13 extra has resolved to, 13.4.59 (what pip install gpuwm[gpu-cu13] installs today) and 13.3.33. On a recorded platform the estimate prices Noah-MP from that platform's own reading. On any other card the Noah-MP frames are priced the way every other kernel is priced on an unrecorded platform, from the ceiling over the recorded platforms, and gpuwm check states that basis beside the verdict ("Noah-MP local frames priced from the ceiling over the recorded platforms ...; not measured on this card"). Either way gpuwm check and gpuwm run admit Noah-MP with no flag; tools/measure_noahmp_frames.py measure, run on a card in its own environment, produces the row that makes its price a reading.
• Playback: the first pass may wait while remote frames enter the local cache. Startup compilation and input preparation also affect reported overall simulation speed.
• Known interface issues: some preview sources remain unavailable, exported dateline-crossing outlines can show a seam, and a background compact-store worker can report an error during the forecast-completion transition. The release qualification documents the retained limits.

ArWen is research and educational software. Use official meteorological services for forecasts and safety warnings. The project is not affiliated with or endorsed by NCAR or UCAR.

Report an issue

Include the version, platform, what you attempted, and the relevant error. gpuwm report RUN_DIRECTORY --output diagnostics.zip collects a diagnostic report with recognized sensitive patterns redacted. Review it before sharing: raw copied logs can contain local paths, usernames, hosts, and configuration details, and no redaction tool guarantees anonymity. Never post credential files or private keys. See reporting a problem.

Development and licensing

Development combines human direction, AI-assisted implementation, and numerical and runtime verification. The source, scientific provenance, tests, and release qualification records are available for inspection.

For a developer installation from a source checkout, use bash install.sh on Linux or powershell -File install.ps1 on Windows. Source installations build the native components and need the corresponding build tools. The explicit bash install.sh invocation also works when an extracted source archive has lost executable permission bits; use it if ./install.sh reports Permission denied.

The engine is licensed under the Apache License 2.0. The desktop application and its dependencies carry their own licenses and notices in the desktop archives. Third-party code, tables, and datasets retain their respective terms; see NOTICE and scientific provenance.