PredictWind Weather Routing is a powerful tool that can help you safely and efficiently navigate the weather using the world's best weather modelling technology.

This article explains how to use the Sail Routing on the PredictWind Forecast Website.

Log into your account using a laptop or computer at https://forecast.predictwind.com/

At the top of the page, select Fastest Time or Comfort.

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.

We have a large selection of sailboat designs with their own complete set of performance polars; you can select your sailboat from the list or one that you know has a similar performance to your sailboat. This method is preferred over Sail Polars.

Sail Polars are very simple to set up and are suitable for cruising boats, where you cannot select a Predefined Polar. Enter your boat speed at 50. 90. And 160 degrees true wind angle in average 15-knot wind speed conditions. We assume this is the max speed for the vessel, and the boat speed decreases as the wind drops.

It allows you to edit and save your boat polars to match the performance of your boat. Once logged into your account via a PC/Mac, you can change the numbers, being careful to keep the same format.

The boat polar will be automatically saved after you perform a weather route.

To use AI Polars, you must have a DataHub or DataHub Pro and a PredictWind Professional Forecast subscription. Select AI Polar on the Routing Preferences page, then select Use my latest AI Polar to run future routes from DataHub collected Polar Data.. 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 your boat speed drops below 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.

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.

You may also position your green start and red finish waypoints using GPS coordinates by clicking on the Waypoint icon to reveal the Latitude/Longitude of your start & finish positions for editing. Go To and port and starboard rounding waypoints can be added if desired. Please make sure all your waypoints are well in the water. Please note waypoints are generally not required, let the router do it's job.

You can add an exclusion boundary if you wish all routes to avoid a defined area.

You can add an exclusion boundary if you wish all routes to avoid a defined area.

Your route will be calculated using your Sail routing parameters and show eight routes related to the eight weather models, wave and currents.

When you click on the weather model icon bottom right, the Forecast Options Box will open

You are able to change the Forecast Model being shown on the Map page.

Turn on and off GMDSS information.

These include map display types:

Parameters include:

The animation play speed is also adjustable in this pop-out.

The displayed map relate to that model and the associated route. For example, selecting the PWE forecast model corresponds to the red track, and the boat is displayed on the active route. A white dot is shown on the other route as you animate the route forward.

You can turn off one or more of the displayed routes by clicking on toggle routes and clicking on the tick box to turn on or off.

Press the play button or control the display with the time slider or the forward and back arrows at the bottom of the Map.

By clicking on any point on a route line, we get details for that point on the route.

This can also be animated forward and back. Pop up box details below:

This is a detailed set of data and should be analysised.

At the top of the screen, click on Tables. The Wind tables include detailed data along the route for all forecast models. Graphs include many important details along the route, including Wave output data > Roll, Vertical Acceleration and Boat Slamming. Take your time to explore this data set.

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