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How to Calculate a Departure Plan

How to calculate a Departure Plan using the PredictWind App

Nick Olson avatar
Written by Nick Olson
Updated over 2 weeks ago

Departure Planning is the perfect tool for Sailboats and Power Vessels to decide which day to depart on a trip. It is designed for trips as short as 15 Nm or for long offshore passages of 9 days or more. Using the Weather Routing algorithm, the Departure Planning Tool will perform an optimum route for different departure times. A summary table is provided so you can quickly compare the differences for leaving in the next 4 departure times. In addition you can graphically see the boats leaving on the different departure times to see how the weather situation affects your passage. You can shorten the comparison period from 1 day intervals down to 1 hour depending on your passage.

Forecast Models

Select between the global models. ECMWF, SPIRE, UKMO & GFS are generally recommended for longer term and extended passages. The PredictWind models (PWG/PWE) will perform better in short term and coastal passages due to the higher resolution.

Start Time

The start time is the time that you intend to depart on your voyage, you will be comparing the four departure days/times. You can click on the ‘Now’ button to use the current time, and ensure that you have the correct time format.

Departure Planning Steps using the PredictWind App

  • Open the PredictWind App

  • On the main menu go to Departure planning

  • Select between Sail Planning and Power Planning.

  • Open up settings using the wheel icon top right

  • Select 4 Forecast Model by opening Preferences, Select the models you wish to compare for your departure times.

  • Return to the Sail Planning or Power Planning Map page.

  • Move your green start waypoint and red destination waypoint to your desired locations, you can drag and drop the waypoints or select the waypoints icon and set the point by entering a lat and long position manually.

  • Select the start time by selecting the clock icon.

  • Here is where you select your time zone and start date for the first departure. Then you can select the spacings between departures. Return to the Map page

  • Click on the download arrow icon top right under the wheel icon.

  • Your 4 departure time routes will be calculated for each of the 4 models you selected.

  • Once your departure routes are calculated, Select Tables

  • Here you can see a summary of each departure time averaged across all 4 models, take time to analyse how each departure time affects your passage.

  • Select the detailed view which shows the breakdown of each model for each departure time allowing you to see the variation between models.

  • Return to the Map view

  • Press Play to animate the Map, each boat will leave at the designated departure spacings. This gives you an overview of the weather systems influencing the departure times.

  • You can see the routes relative to the different models.

  • Focus your departure time by hiding routes you don't want to see.

  • Once you have selected a possible departure time. You can run a weather route with that start time to further analyse the passage and the conditions you are likely to encounter.

See below the wind angles we use to define upwind/reaching/downwind.

% time upwind = True Wind Angle is 55 degrees or less.
% time reaching = True Wind Angle is between 55 degrees and 135 degrees.
% time downwind = True Wind Angle is 135 degrees or more.

Please click here for more How to use Departure Planning Results.

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