Weather Forecast Controls
The panel that drives how weather is drawn on the map: wind, pressure, waves, currents and sea level, with a choice of visual styles, a day selector, an hour slider and a play-back animation.
Where to find it
On the map, click the Forecast button (sun/cloud icon) overlaid on the chart. The panel opens with two tabs at the top: OpenMeteo (online forecast) and GRIB (loaded weather file).
For the visualizations to actually appear on the chart, the Forecast layer must also be enabled in the Overlays panel. If it isn't, the panel shows the reminder: "Enable "Forecast" in Overlays to display on map".
Hierarchy
Forecast (map panel)
├── OpenMeteo tab
│ ├── Zone source: Route | Zone
│ │ ├── Route → Load forecast for route / Clear forecast zone
│ │ └── Zone → Draw zone on map
│ ├── View mode: Wind | Pressure | Waves
│ │ ├── (Wind) Styles: Barbs · Arrows · Heatmap · Flow · WebGL · Waves
│ │ └── (Waves) Sub-modes: Height · Decomp. · Cross Sea · Wave Flow
│ ├── Marine data: Current Forecast | Sea Level
│ ├── Day selector: Today · Tom. · +2 … +6
│ └── Hour slider: 0–23 h or All day
└── GRIB tab
├── (same display controls as above, on a loaded GRIB)
├── Day selector (grouped from the GRIB time steps)
└── Time-step slider with Play / Pause (animation)
Note: downloading and importing GRIB files is covered on a dedicated page. This page documents only the display controls shared by both tabs.
Zone source
Route / Zone
What it does: defines the geographic area for which forecasts are fetched. While online, forecasts are loaded only for an explicit zone, to save the API call quota. Without a zone, nothing is displayed.
How to use it: 1. Pick Route to cover the extent of your active route, or Zone to draw a free rectangle. 2. In Route mode, click Load forecast for route (needs at least 2 waypoints). The computed extent is shown as coordinates (South–North N · West–East E). 3. In Zone mode, click Draw zone on map, then click-and-drag on the chart to draw the rectangle. While drawing, the button blinks and reads "Click & drag on map...". 4. To remove the zone, click Clear forecast zone (Route mode) or the small cross next to the draw button (Zone mode).
Options & settings:
| Control | Role |
|---|---|
| Route | Fetches forecasts over the active route's extent. |
| Zone | Enables drawing a free rectangle on the map. |
| Load forecast for route | Computes the extent from waypoints and starts fetching. Disabled with fewer than 2 waypoints. |
| Draw zone on map | Switches to draw mode; click-and-drag to set the zone. |
| Clear forecast zone / cross | Removes the zone and clears the displayed forecast. |
Tips & limits: - While online, no zone = no data. This is deliberate, so panning the map does not burn API quota. - Once the zone is drawn, panning or zooming does not trigger new calls: everything is loaded for the zone. - Offline, the app falls back to the visible map extent and serves whatever is cached.
View mode
Wind / Pressure / Waves
What it does: selects which weather parameter is rendered on the map. Only one mode is active at a time.
How to use it: 1. Click Wind, Pressure or Waves. 2. Depending on the mode, a row of styles (Wind) or sub-modes (Waves) appears just below.
Options & settings:
| Mode | What it shows | How to read it |
|---|---|---|
| Wind | Surface wind (speed, direction, gusts). | Then pick one or more styles (see below). Hover a symbol for the detailed tooltip: speed in knots, cardinal direction, Beaufort force, gust, pressure, cloud cover, precipitation. |
| Pressure | Mean sea-level pressure + 3-hour barometric tendency. | Each tag shows pressure (hPa) and the /3 h change, with a colored arrow (rising/falling). A fast drop shows a pulsing ring: a heads-up for squalls or a blow. |
| Waves | Sea state (height, swell, period). | Then pick one or more sub-modes (see below). The tooltip details total height, period, energy/power, wind sea, primary and secondary swell, cross sea, comfort score and sea-surface temperature. |
Tips & limits: - In Pressure mode, the icon switches from the "pressure" color to the "tendency" color as soon as the barometer moves: a quick visual cue for deteriorating areas. - The wave color scale runs from calm (cool tones) to heavy weather (warm tones). Always hover a symbol for the exact figures.
Wind visual styles (Wind mode)
Barbs · Arrows · Heatmap · Flow · WebGL · Waves
What it does: chooses one or more representations of the wind field. Several styles can be active at the same time (they stack).
How to use it: 1. Switch to Wind mode. 2. Click one or more style buttons; an active style is highlighted. Click again to turn it off.
Options & settings:
| Style | Button label | How to read it |
|---|---|---|
| Barbs | Barbs | Classic weather barbs. Each half-feather = 5 knots, full feather = 10 knots, pennant = 50 knots. The shaft points to where the wind comes from. Color by force. The most precise read for a sailor. |
| Arrows | Arrows | Simple arrows colored by force, pointing in the direction the wind is going. Quick read of the general direction. |
| Heatmap | Heatmap | A continuous color gradient (heatmap) of wind intensity. Ideal to spot strong and light areas at a glance. |
| Flow | Flow | Animated particles following the wind flow (trails). Conveys motion and direction. |
| WebGL | WebGL | High-density GPU-accelerated animated particle field (WebGL). Smooth rendering of thousands of particles, denser than Flow. |
| Waves | Waves | Animated particles following the wave direction (not the wind), to visualize the sea flow even in Wind mode. |
Tips & limits: - Barbs is the reference style for judging a point of sail; Heatmap + Barbs combines the big picture with local precision. - Animated styles (Flow, WebGL, Waves) are heavy: over a large zone or on a modest machine, prefer Barbs or Heatmap. - Styles only appear in Wind mode.
Wave sub-modes (Waves mode)
Height · Decomp. · Cross Sea · Wave Flow
What it does: breaks the sea state into several complementary reads. Several sub-modes can be active at once.
How to use it: 1. Switch to Waves mode. 2. Enable one or more sub-modes; an active sub-mode is highlighted.
Options & settings:
| Sub-mode | Button label | How to read it |
|---|---|---|
| Height | Height | Wave symbols (concentric arcs + direction arrow + meter label) and a colored heatmap by significant height. A pulsing ring flags the presence of swell; the longer the period, the slower the pulse. |
| Decomp. | Decomp. | Swell decomposition: separates the wind sea from the swell(s) so you can read their respective directions and heights. Useful to make sense of a confused sea. |
| Cross Sea | Cross Sea | Highlights cross-sea areas (swell and wind sea crossing at a wide angle). Color by angle; warns of uncomfortable, even dangerous conditions. |
| Wave Flow | Wave Flow | Animated particle field (WebGL) following wave propagation. Dynamically shows the direction and speed of swell propagation. |
Tips & limits: - A wave symbol's tooltip also gives the comfort score /100 and a numeric cross-sea warning (angle + risk level). - Decomp. and Cross Sea are valuable on an ocean passage to anticipate awkward seas even in moderate wind. - Sub-modes only appear in Waves mode.
Marine data
Current Forecast / Sea Level
What it does: overlays two oceanographic layers, independent of the chosen view mode.
How to use it: 1. Click Current Forecast to show forecast currents, and/or Sea Level for sea level. 2. Click again to hide.
Options & settings:
| Toggle | Role |
|---|---|
| Current Forecast | Shows the forecast surface current field. |
| Sea Level | Shows the sea-level variation. |
Tips & limits: - Both toggles are available from both tabs (OpenMeteo and GRIB). - Current can add or cost several knots over the ground: cross-reference it with the wind to optimize your course.
Day selector
Today · Tom. · +2 … +6
What it does: chooses the displayed lead time, from today out to +6 days.
How to use it: 1. Click the desired day: Today, Tom., then the abbreviations of the following days (up to 6 days). 2. Selecting Today automatically snaps the hour slider to the current hour; selecting another day switches to the All day (aggregate) view.
Options & settings: - 7 buttons: today (Today) and the next 6 days, labeled with the weekday abbreviation.
Tips & limits: - In the GRIB tab, the offered days are derived from the time steps actually present in the file: there may be fewer than 7 depending on the GRIB's lead time. - Beyond a few days, trust the ensembles (spaghetti) more than the deterministic value.
Hour slider
What it does: narrows the display to a specific hour of the day, or returns to the daily aggregate.
How to use it:
1. Drag the slider from 0 to 23 to choose the hour (shown as HH:00).
2. Drag all the way right (position 24) to return to All day mode: the forecast then shows the day's aggregated values.
Options & settings: - Range 0–23 h; far-right position = All day (aggregate). - The clock icon on the left signals that this is the time control.
Tips & limits: - In All day mode, pressure shows the worst tendency of the day (handy to spot a deepening risk), whereas in hourly mode it shows the live 3-hour tendency. - An "Updated … ago" indicator (pulsing green dot) and the source "Source: Open-Meteo (ECMWF/GFS)" appear at the bottom in the OpenMeteo tab.
Animation (Play / Pause) — GRIB tab
Animated time-step slider
What it does: automatically steps through the time steps of a loaded GRIB file, like a weather animation loop.
How to use it: 1. In the GRIB tab, once a multi-step file is loaded, the time-step slider appears, preceded by a Play button. 2. Click Play (triangle) to start the animation: the slider advances one step every 1.5 s and loops back to the start after the last step. 3. Click Pause (two bars) to stop; touching the slider also pauses the animation.
Options & settings: - Play / Pause button (green when active). - Time-step slider: each position is a lead time, whose label (date/time) is shown under the slider. - The day selector above jumps directly to the first step of each day.
Tips & limits: - The animation only exists in the GRIB tab (it animates the file's time steps). The OpenMeteo tab offers the day selector and hour slider, but no auto play-back. - While a step is changing, a loading indicator briefly replaces the clock icon.
Boat-conditions compass
"Conditions as seen from the boat" compass
What it's for: a floating card over the chart with a compass dial (north up) and the boat hull rotated to its course. It shows the conditions at the boat's position for the chosen forecast time — wind, waves, current — plus your point of sail and the recommended sails, and updates live as you scrub the timeline. Perfect for "seeing" what awaits the boat along the track before you leave.
How to use it: 1. Prerequisite: an active route — the isochrone-optimized route if you computed one, otherwise simply your active saved route. No need to run routing or turn on the Isochrone overlay. 2. The card is open by default. If closed, click the round compass button at the top-right of the map ("Boussole conditions bateau"). 3. Scrub the forecast time slider: the boat's position along the route, its heading, speed, remaining distance, and the wind / wave / current arrows all update to that moment (in step with the animated boat marker on the map). 4. Move the card by dragging it (grip in the header); its position is remembered between sessions. 5. Close it with the X: the card collapses back to the round button.
Options & settings:
| Element | What it shows |
|---|---|
| Header | Title Conditions vues du bateau + date/time in UTC (e.g. Wed 22 Jul · 14:30 UTC). |
| Wind arrow | True wind direction + speed in knots. |
| Waves arrow | Direction + significant wave height in metres (shown when there is any sea). |
| Current arrow | Speed in knots, colour-coded by effect on your course: green = favourable, orange = against, blue = beam. |
| Points-of-sail ring | Colour bands around the dial (close-hauled · close reach · beam reach · broad reach · running), rotated with the wind and mirrored on both tacks. The current point of sail is highlighted (brighter fill, larger label). |
| Sails on the hull | Mainsail + headsail drawn, heeled to leeward by the wind angle; reef lines shown; headsail type coloured (spinnaker/gennaker purple, genoa green, staysail orange, storm jib red). Motoring: sails hidden, a small M behind the transom. |
| Recommended sails | Row under the KPIs: colour dot + label of the recommended sail combination for the current leg. |
| Vitesse (Speed) | Boat speed (kn). |
| Cap (Heading) | Course over ground (°). |
| Restant (Remaining) | Distance remaining to arrival (nm). |
| Leg sélectionné (optional) | Appears when you highlight a leg in the sail-plan table: leg avg wind (kn), distance (nm) and duration (Hh MM). |
Tips & limits: - The card appears as soon as there is an active route (optimized or simply saved) and a forecast time — no isochrone needed and no Isochrone overlay. It only disappears when there is no active route. - It is tied to the forecast scrubber, not the real-time clock: it's a planning tool, not a live instrument. - Tip: clicking a route waypoint snaps the forecast scrubber to that point's estimated time of passage; clicking a sail-plan leg snaps it to the leg's mid-time and highlights it (the "Leg sélectionné" block). - The points-of-sail ring uses the same bins as the sail-plan table, so the compass and the plan never disagree. - Its labels are in French whatever the app language (not yet translated). - The Leg sélectionné block requires selecting a leg in the sail-plan table.
Meteogram (right-click)
Meteogram
What it's for: show a multi-day time series (up to 6 days) of the forecast at one exact map point: wind, gusts, direction, pressure and precipitation.
How to use it: 1. Right-click the map where you want it → context menu. 2. Choose Meteogram here. 3. The chart opens for that point (the menu also offers Add waypoint / POI).
Options & settings:
| Element | What it shows |
|---|---|
| Wind | Wind speed (cyan area). |
| Gust | Amber line. |
| Dir | Direction arrows every 6 h. |
| Pressure | Purple line (hPa). |
| Precip | Blue bars (mm). |
| Hover | Reads values at the hovered hour: time, wind, gust, direction (° + cardinal), pressure, precip. |
Tips & limits: day gridlines/labels + a wind scale (every 10 kt). The meteogram fetches its own forecast for the point (independent of any loaded GRIB): "Loading forecast…" while fetching, "Forecast unavailable for this point." on failure. Close with the X, the backdrop, or Esc.