HWS provides wave climate statistics across 104 ocean areas, derived from ECMWF ERA5 hindcast reanalysis. Scatter diagrams, directional analysis, and seasonal breakdowns · free for the maritime community.
Hs–Tz Scatter Diagram
Area 15 · North Atlantic
Significant Wave Height (Hs) vs Zero-Crossing Period (Tz)
About HWS
HWS uses ECMWF ERA5 reanalysis · one of the most comprehensive atmospheric and ocean wave datasets ever produced · to generate wave climate statistics across 104 ocean areas widely used in the maritime industry.
ERA5 computes wave fields at every ocean grid point at 0.5° resolution, hourly. All 104 areas are covered uniformly: open ocean, coastal zones, polar regions, and the Southern Ocean alike.
Significant wave height and zero-crossing period are derived from the ECMWF spectral wave model. Physically modelled rather than visually estimated, ensuring consistent and reliable scatter diagrams.
ERA5 wave data is continuously validated against satellite altimetry (Jason, Sentinel) and in-situ wave buoy networks, with documented accuracy within 0.3 m RMSE for significant wave height globally.
Physics-based numerical models capture the full spectrum of sea states including extreme events. The hindcast data reflects the actual physics of the ocean as it happened, validated against buoy and satellite records.
Select and analyse multiple ocean zones simultaneously. Zones are displayed on an interactive map and results are combined into a single scatter diagram with a clear analysis summary.
HWS is built on open Copernicus data and provided free of charge. We believe high-quality wave statistics should be accessible to every naval architect, engineer, and researcher who needs them.
Capabilities
HWS provides a focused set of wave climate tools designed for practical maritime engineering use: select zones, filter by season and direction, and get scatter diagrams instantly.
Wave scatter diagrams showing occurrence counts of significant wave height vs zero-crossing period for all 104 ocean areas. Standard 1 m and 1-second binning with row and column sums.
Select one or more ocean zones directly on an interactive world map. Zones are numbered 1–104 and can be searched, multi-selected, or cleared with a single click.
Filter scatter diagrams by 8 compass directions (North, Northeast, East, Southeast, South, Southwest, West, Northwest) or view all directions combined.
Select any combination of months to analyse seasonal wave patterns. Choose individual months, winter/summer seasons, or any custom grouping to match your operational needs.
Extract raw hindcast wave data for selected zones and time periods. Access the underlying ERA5 wave fields directly for custom analysis and processing.
Download scatter diagrams and extracted wave data as Excel files. Ready for use in loading computers, seakeeping tools, structural design software, or your own analysis workflows.
How It Works
HWS is free to use. Create an account, select your zones and time range, and download your results. No credit card required.
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Pick one or more zones on the interactive map, set the hindcast year range (1995–2026), and select which months to include.
View Hs–Tz scatter diagrams with directional filtering online, or export directly to Excel for use in your own tools and workflows.
Applications
From hull structural design to cargo lashing calculations, HWS serves every discipline that relies on long-term wave climate statistics.
01
Scatter diagrams feed directly into spectral fatigue analysis and long-term load calculations per classification society rules. Export to Excel and use in your existing design workflows.
02
Zone-specific and seasonal wave data enables refined acceleration calculations for cargo lashing, supporting both standard CSS Code calculations and route-specific approaches.
03
Combine vessel RAOs with HWS scatter diagrams to compute operability indices, motion sickness incidence, and slamming probability across global trade routes.
04
Use seasonal and directional wave data to assess operational weather windows for offshore lifts, towing, and marine transport. Filter by month to understand conditions during planned operations.
05
A freely accessible wave climate reference for university courses, academic research, and student projects in naval architecture, ocean engineering, and coastal science.
06
Quick lookup of wave conditions in any ocean area. Useful for preliminary feasibility studies, proposal writing, and understanding wave environments along planned shipping routes.
Data Source
ERA5 is the fifth-generation atmospheric reanalysis produced by ECMWF for the Copernicus Climate Change Service, one of the most widely used and extensively validated environmental datasets in the world.
ERA5 uses a state-of-the-art 4D-Var data assimilation system to blend observations from thousands of sources (weather stations, radiosondes, ocean buoys, aircraft, satellites) into a physically consistent gridded dataset spanning the globe at 0.5° horizontal resolution.
For wave climate, ERA5 employs the ECWAM third-generation spectral wave model, which explicitly resolves wave generation by wind, swell propagation, and wave-wave interactions. Output is produced hourly from 1940 to near-real-time, providing a continuous record of sea state at every ocean grid point.
The ERA5 wave dataset has been extensively validated against both in-situ buoy networks and satellite altimetry (Jason-2, Jason-3, Sentinel-6), achieving documented RMSE of approximately 0.3 m for significant wave height globally.
| Dataset | ECMWF ERA5 Reanalysis |
| Coverage | Global, 1995 to present |
| Spatial Res. | 0.5° (~30 km at equator) |
| Temporal Res. | Hourly output |
| Wave Model | ECWAM (spectral, 3rd gen.) |
| Assimilation | Satellite altimetry + SAR spectra |
| Validation | ~0.3 m RMSE vs. buoys globally |
| Licence | Copernicus CC-BY (free use) |
Contains modified Copernicus Climate Change Service information (2026). Neither the European Commission nor ECMWF is responsible for any use that may be made of the information it contains.
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