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How to use Weather Routing on the website
How to use Weather Routing on the website

How to use Sail Routing on the Forecast Website

Jon Bilger avatar
Written by Jon Bilger
Updated over a week ago

The PredictWind Weather router 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 Weather router for Sail routing on the PredictWind forecast Website. For Powerboat Routing, please see the PowerBoat Routing collection.

Sail Routing on the Forecast Website

This quick animation video briefly overviews how to access and use Sail Routing.

Get started with Sail Routing on the Forecast Website

To get started with Sail Routing:

Routing Preferences

Optimize Route for

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

If you select Comfort, you must specify the additional conditions you wish the router to avoid. The route will still try to optimise for speed but will avoid the specified conditions.

Fastest Time

This will optimize the route for the quickest possible time.


This will optimise the route for the fastest time but avoid high wind/wave regions in the forecast. You set your criteria for high wind and wave areas to avoid when you select Comfort. The minimum values for Wind Speed and Swell are 25knots and 2.5m. This is set as lower values can result in optimal routes that are very long, trying to avoid these conditions.

These are critical settings. If you find a route can't be calculated, or an odd route is suggested, please adjust these settings upwards to increase the range of conditions available for the optimized route to follow. We recommend using the defaults or higher settings if you're comfortable with those.

Set your Boat Polar

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.

Sail Polars

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

Advanced Polars

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.

AI Polars

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.

Will motor at x knots when boat speed is less than y knots

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.

Depth Avoidance

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.

Ocean and Tidal Currents

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

Advanced Routing Adjustments

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.

Run a Sail Route

Now your boat parameters, dimensions and routing preferences are configured, select the Sail Routing tab. Drag and drop the green Start Waypoint and the red Finish Waypoint to your desired locations.

Routing Options

You may also position these using GPS coordinates by clicking on the Waypoint icon to reveal the Latitude/Longitude of our start & finish positions for editing. You can also add port and starboard rounding waypoints if desired. Please make sure all your waypoints are well in the water. To add Waypoints:

  • Click on the Waypoints icon.

  • Click on Waypoints.

  • Click the + symbol to add Waypoints.

  • Drag and drop your Waypoints to the desired locations.

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

To add a Boundary:

  • Click on the Waypoints icon.

  • Click on Boundaries, then Create Boundary.

  • Click on the map where you want to add a boundary and sufficient points to make it a closed shape. Once you have the points on the map, you can move each point and add a lat/long if you wish to be specific.

  • To delete the boundary, click on the centre and delete.

Run a Sail Route

You can now calculate your sail route route; click the Download button. Your route will be calculated using your Sail routing parameters and show six routes related to the six weather models, wave and currents.

When you click on the weather model from the bottom right, a control panel will pop out; you can change the display here. Click on Extreme weather warnings to read GMDSS forecast alerts.

Forecast Options

  • ECMWF is Black

  • UKMO is Yellow

  • Spire is Orange

  • PWG is blue

  • PWE is Red

  • GFS is Green

Display Controls

These include map display types:

  • Streamlines

  • Wind barbs with colour contours

  • Wind arrows with colour contours

Display Parameters

Parameter selections which you can select here include:

  • Wind

  • Currents

  • Rain

  • Cloud

  • Air temperature

  • Gust

  • Cape

  • Wave

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

Route Display & Use

Wind Maps

The displayed wind maps relate to that model and the associated route. For example, selecting the PWE model corresponds to the red track, and the boat is displayed on the active route.

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. Click x to close.

Animate the route

Press the play button or control the display with the time slider ball or the forward and back arrows.

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

Routing Tables

At the top of the screen, click on Tables. The tables include detailed data about your routes for all models. We have Graphs with many important details along our route, including the Roll, Vertical Acceleration and Boat Slamming.

We also have the Export function, which allows you to export the weather route in several digital formats for Navigation software.

Click on the Map button to go back to the routing Map.

Congratulations! You are now ready to use the PredictWind Sail routing!

PredictWind Weather routing video

Please note that this video is old, and some of the website layout has changed; however, the information explained is relevant and accurate. Current website screenshots are above.

Related Articles

Click below to read more articles about Weather Routing:

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