Weather Routing preferences can be set in the PredictWind App on the Sail Routing page by tapping on the Settings wheel.

You can also set Routing Preferences within the Sail Routing page on the Forecast website. Click on Sail Routing, then click on Routing Preferences.

For information about Powerboat Routing, please see the PowerBoat Routing collection.

This will optimize the route for the quickest possible time.

Comfort Routing is based on boat motion modelling, which evaluates roll, vertical acceleration and slamming.

The default comfort thresholds are set to avoid roll (RMS) greater than 4.0°, avoid vertical acceleration greater than 0.2 g, and avoid slamming incidence greater than 50%. Whilst these recommended default settings may not be comfortable, the router will, where possible, avoid unsafe and very uncomfortable conditions. It is very important that you select the best departure day using the departure planning tool first.

When you request a route, the router will first attempt to calculate a route that stays within these comfort limits. If it cannot complete the route within those parameters, it will automatically rerun the route without comfort limits so you still receive a result.

You can also modify the comfort settings or turn Comfort Routing off entirely in any route request to suit your boat, crew and conditions.

It is important to set up Wave Polars for your boat so the motion modelling works correctly. In your routing preferences, you should enable Wave Polar and enter your boat dimensions, including the type of boat, displacement, LWL (waterline length), beam and draught. These parameters allow PredictWind to model roll, acceleration and slamming more accurately for your specific vessel.

Polars define the performance of your sailboat in different wind/wave conditions. It is essential to define this accurately so the optimal route is correct. You have the option to adjust the speed and apply penalties for tacking and gybing:

A list of popular sailboats are listed as predefined. Select the closest yacht from the drop-down list.

Similarly, this lets you define a basic polar curve for a sailboat. Simply fill in the boat speeds for the different conditions, and the performance curve will be calculated.

It allows you to edit and save your custom polar curve to match the performance of your boat. You will need to do this from a PC/Mac computer. Once logged into your account via a PC/Mac, you can change the numbers, being careful to keep the same format and spacing. Please use spaces, not tabs. The polar will be automatically saved after you perform a route.

Selecting AI Polars uses your boat's latest stored polar on PredictWind's servers to provide polar data for calculating the best route. To use AI Polars requires a DataHub and PredictWind Professional Forecast subscription. To learn more about it, please see this article: AI Polars - DataHub Automatic Polar Generation.

When this setting is enabled, the route calculated will assume that you will motor at a set speed when the wind is insufficient to achieve a particular sailing speed.

This can be set to Land, 2 metres, 5 metres, up to 30 metres. Please check all your waypoints are in clear open ocean for best results. If you find the router cannot calculate a route or the routing calculated is odd, please try adjusting this setting to the lowest safe setting for your boat or add waypoints to your course in deeper water.

The routing algorithm uses ocean/tidal current data if this option is selected. You can choose tidal and ocean currents based on the Mercator or RTOFS models. Mercator is recommended and set by default.

These optional settings allow you to scale True Wind Speed and True Wind Direction.

TWS Scale Factor - True Wind Speed Scale Factor applies a scale factor to the Wind speeds used for weather routing. This is useful if the forecasts generally predict higher or lower wind speeds than the onboard wind gear. This is a percentage, so as an example, setting it at 95% means you believe the actual wind speed is 5% less than the forecasts.

TWD Adjustment - True Wind Direction Adjustment applies an adjustment to the Wind Direction used in weather routing. This is useful if the forecasts generally predict an offset wind direction compared with the onboard wind gear. This is a change in degrees, so as an example, setting it to -5 means you believe the actual wind direction is 5 degrees more to port. Top navigators rarely use the TWD adjustment, so we do not recommend changing this value.

The TWD adjustment and TWS scale factor are predominately racing navigator tools, running several weather routes daily during a race with well-calibrated wind instrumentation.