Weather Routing Advantages
Weather Routing consists of finding the optimum routes between 2 points. Indeed, the shortest distance will very rarely be the quickest route. This will only be the case in exceptional circumstances such as: absence of wind, currents and waves.
The calculation of the best route should integrate various data:
- Boat and sails performance
- Wind forecast
- Tide and oceanic currents
The objective of weather routing is generally to propose the quickest route to the skipper. This is the case for offshore racers. For the cruiser, objectives may be different:
- Avoid sailing in too strong winds and gusts
- Arrive at destination during daylight, when harbor lock is open or more simply be on time for a dinner with friends
- Minimize fuel consumption or engine noise
- Avoid uncomfortable points of sail such as close hauled.
- Avoid areas where sea state is difficult : high waves, choppy or crossed sea
A good piece of software is able to integrate all the required data and to suggest to the skipper the best route, taking into consideration its objectives.
The computer needs to know:
- The boat performance curve (also known as Polar or Velocity Prediction Program) that gives the speed of the boat as a function of wind speed and the angle between the wind and the boat’s course.
- Weather forecast data (wind and gusts, currents and waves)
- Cartographic data (sea or ground)
- The starting point
- The arrival point
- Optionally waypoint(s) or stopover(s)
Once the software knows your boat and its sail sets, your preferred weather data sources, and your navigation preferences that are set during software install: wave height, wind and gusts strength, speed limit below which you switch on the engine, etc.) ….
It should be able to answer a very simple order:
“I am here, I want to go there and I want to start at this time”! Tell me what is the best route!”
The routing software should indicate not only the route points (position, course, speed, wind angle, etc) but also give a clear and synthetic summary of the planned cruise: duration, sailing and motoring time, wind and sea conditions, waves, risks of storm, etc …so that the skipper can easily decide on the appropriate start.
Once the proposed route is accepted, it will be converted into a navigation route. Indeed, the router proposes a theoretical route that needs to be simplified and tuned to avoid hazards, or minimize number of tacks. The navigation should always been monitored on a precise nautical map (NOAA, SHOM, etc).
When at sea, the skipper only needs to indicate the next active point and the router will give the helmsman the necessary navigation information at any time: Course and distance to next point, speed, Time To Go, etc… It will also display the position, speed and course of all boats around that are equipped with an AIS (Automatic Identification System) beacon.
All this looks pretty simple and straightforward, but weather routing applications are only used by very few skippers, despite the safety, comfort and performance that they bring. Why?
- Most of the routers are very awkward to use and often require a PhD level to be mastered.
- The skipper does not know how to calculate his boat’s polar curve, and does not want to buy an additional piece of software to compute them.
- The skipper should not worry about getting « grib files » (standard weather forecast data format). But in fact a good software should be able to get automatically the weather data, once the start, arrival and departure time are known
As a conclusion, one should never forget that the router is only a tool to help the skipper to make the right decisions. It will never become « the only master on board after God! “
A general presentation of Avalon Offshore is available on youtube