From forecast conditions to a comfort score#
FairlySoon estimates how demanding a passage may feel from the conditions your boat is forecast to encounter along the way. It follows the boat through place and time, rather than judging the whole passage from the weather at departure.
Conditions contribute to discomfort along each part of the route. Those contributions are combined and weighted by the time spent in them. The overall comfort score expresses the average discomfort as a number from 0 to 100; higher means more comfortable under your selected preferences. It is not a probability of safety, and a high average can still contain an unpleasant stretch. The comfort graph helps you find those stretches.
The Comfort routing option balances time at sea against accumulated discomfort. A gentler detour can be worthwhile, but extra hours at sea also count. Speed prioritises passage time. See Reading your results for how the resulting passages and departure windows are compared.
Three comfort settings#
Choose a preference in Settings → Planning. All three settings use the same forecast inputs, with different parameters controlling when some conditions start adding discomfort and how quickly their contribution increases.
| Setting | What changes |
|---|---|
| Gentler | Starts adding discomfort at lower wind strengths, gustiness and wave heights, and reaches a strong penalty sooner. It also responds sooner to rain and atmospheric instability. |
| Balanced | The default, using FairlySoon's standard offshore comfort assumptions. |
| Tolerant | Allows stronger wind, greater gustiness and higher seas before adding the same discomfort. It also responds later to rain and atmospheric instability. |
For example, the same stretch of gusty weather and short, steep seas can score lower with Gentler than with Tolerant. Not every parameter changes: the treatment of wind angle, wave direction and steepness, and lightning probability is shared across the three settings.
Changing the preference can change scores, routes and departure rankings when you calculate again. Keep the same preference when comparing options. These are comfort preferences, not hard exclusion limits or a change in the boat's physical capabilities. Individual comfort parameters are not currently editable; choose the preset that best fits your crew. Boat performance and motoring are configured separately in Boat and comfort settings.
Which forecasts affect the calculation?#
| Forecast input | Movement and arrival time | Comfort calculation |
|---|---|---|
| Wind speed and direction | The boat polar gives sailing speed for the wind strength and angle to the boat. | Stronger wind and sailing upwind add discomfort. |
| Currents | Affect progress over the ground and the heading needed to hold a course. | No separate current penalty; they can change the route, duration and conditions encountered. |
| Gusts | Do not directly increase or reduce the polar’s boat speed. | Gustiness adds discomfort according to how much gusts exceed the mean wind. |
| Wave height, direction and period | Do not directly reduce the polar’s boat speed. | Higher seas, their angle to the boat and their steepness affect discomfort. Period helps distinguish a long swell from short, steep seas. |
| Rain rate | No direct speed effect. | Heavier rain adds discomfort. |
| CAPE | No direct speed effect. | Convective instability adds discomfort; CAPE is not a lightning probability. |
| Lightning probability | No direct speed effect. | The Met Office three-hour lightning probability adds discomfort where coverage is available. |
For example, a favourable current can shorten a passage under either objective. A band of short, steep waves can make the Comfort calculation choose a different route, while Speed does not detour to avoid waves. Waves can therefore change the comfortable route and its arrival time without being a direct reduction in the boat’s calculated speed. Real boats may slow in seas more than the polar predicts.
Shown for inspection, not included in the calculation#
Pressure, cloud cover, air temperature and sea temperature do not directly affect route choice, calculated boat speed or comfort scores. GMDSS marine warnings are also shown for you to read; the solver does not interpret their bulletins or route around their warning areas. For example, a pressure change or a warning on the map does not itself lower a comfort score.
The map layer you choose to display does not choose the solver’s inputs: switching to Pressure or Rain does not turn wind or currents off. To change the calculation, change the planning or boat settings and calculate again.
These inputs depend on the available forecast fields and coverage. A missing gust field cannot contribute a measured gust penalty; stretches beyond the lightning forecast are omitted from its lightning penalty. A missing field is not evidence of benign conditions. Check the coverage notes explained in Understanding the graphs, inspect hazards independently and read Safety and limitations before deciding to sail.