The Passage Planner plugin adds professional routing functions for sailors to the popular Windy weather app, at least according to the description. Unlike the established competition from Navimetrix, PredictWind or Squid Mobile, Windy weather routing is integrated directly into the app interface and utilises its extensive range of global weather models. The plugin is part of the Windy Premium subscription, which costs 19 euros per year. The routing function is only available after registration and can be installed via the Windy app or the browser version.
Installation and first steps
After installation, a new button for the Passage Planner appears in the top right-hand corner of the Windy interface. Operation follows the usual pattern: In the settings, you select which of the weather models offered by Windy is to be used. Several models can also be selected; this automatically creates a multi-routing. The boat type must also be specified. The database currently only contains 23 polar diagrams, but can be easily expanded. Finally, at least the start and end points of the trip are set on the map and the calculation is started. Depending on the number of weather models selected and the length of the route, however, the calculation may take longer or even much longer: If there are several models, they are calculated one after the other, which significantly increases the waiting time. The calculated routes are displayed in different colours.
Practical test on the Baltic Sea: implausible route suggestions
We tested Windy weather routing on the Baltic Sea. The test route from Flensburg Fjord to Ystad in Sweden - around 141 nautical miles as the crow flies - delivered mediocre results. The route suggestions calculated by the plugin sometimes showed very unusual courses: In several cases, the system suggested sailing back a bit, although this diversions could not be plausibly explained from the underlying weather data. When manually comparing the wind directions and strengths in the Windy charts, the suggested course appeared incomprehensible.
A direct comparison with Navimetrix revealed clear differences: the same route with identical settings - the same boat type, the same weather models and the same start and destination coordinates - was calculated much faster by Navimetrix and looked much more realistic. The Navimetrix route followed a more logical course without the strange backward movements suggested by the Passage Planner.
Multi-planning with a good overview
The multi-planning function of Windy Weather Routing was a positive surprise: it checks different departure times at freely selectable intervals - for example every six hours - and calculates the respective route for each start time. The results are displayed clearly and concisely: Route length, journey duration and average speed, each broken down by weather model. Compact bar charts show wind speeds, wind angles of incidence or the speed over ground during the route at a glance. This makes it easy to see whether a particular starting window is particularly favourable or not.
The problem: Even with multi-planning, strange routes with loops, loops and figure eights that don't make sense in practice can be seen. The good preparation of the data is of little help if the underlying routes are not plausible. The interface and the presentation of the multi-planning are successful - but they cannot make up for the weaknesses of the routing algorithm.
Limits of the Windy map
A fundamental problem with Windy weather routing is that the app does not work with nautical charts, but with a simple map. Depth contours, fairways, buoys and other nautically relevant information are completely missing. This means that the calculated routes must be compared with a real nautical chart in order to recognise shallows, restricted areas or other obstacles. It is questionable how useful the route calculation is if it leads through a wind farm or a traffic separation scheme. It may be sufficient for long offshore stretches.
CONCLUSIONS:
Windy Weather Routing with the Passage Planner plugin is an interesting attempt to integrate professional routing functions into an already widely used weather app. The integration into Windy, the low price of 19 euros per year (including all premium functions) and the well-implemented multi-planning function are clear advantages. The large selection of weather models is also impressive.
In practice, however, the calculated routes showed implausible courses with loops and figure eights that could not be explained by the weather data. This fundamental problem runs through all functions - including the otherwise successful multi-planning function. In a direct comparison with Navimetrix, the competition was significantly faster and provided more comprehensible route suggestions. The lack of nautical chart material in Windy is a further disadvantage: the routes have to be compared with a real nautical chart.
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Hauke Schmidt
Test & Technology editor
