Weather Overlays
All overlays in the Weather category of the overlay panel: they layer wind patterns, hazard zones, pressure, forecast models and satellite imagery onto the chart to plan and monitor a passage.
Where to find it
Map › floating Overlays button (layers icon, top left) › Weather tab (wind icon).
Hierarchy
Overlays (floating panel)
└── Weather tab (wind icon)
├── Wind Roses
├── Ocean Zones
├── Gale Zones
├── Visibility
├── Isobars
├── Synoptic Isobars
├── Model Spread
├── Split View
├── Satellite
├── Lightning
├── Wave Confidence
├── Seasonal Forecast
└── Climate indices
The Overlays panel
What it does: groups every chart overlay by category (Weather, Ship, Routing, Navigation, Safety, Currents, Fishing, Other). Weather is the first category (wind icon).
How to use it: 1. Click the Overlays button at the top left of the map. The number badge shows how many overlays are currently active. 2. The panel opens. Stay on the Weather tab (first tab, wind icon), or click it. 3. Click an overlay name to turn it on; it gets coloured. Click again to turn it off. 4. You can enable several overlays at once.
Options & settings: - Drag handle — the panel is movable: grab the handle (horizontal bar) at the top to reposition it. - Tab badge — each tab shows a small counter of active overlays in that category. - Presets — bar at the top of the panel: the + button (bookmark plus) saves the current overlay combination under a name (e.g. Transat, Coastal); the Presets button opens the list to reload or delete a saved preset.
Tips & limits: - In climatological mode (departure more than 7 days out, with no real-time forecast or GRIB), some overlays are greyed out and not clickable: Visibility, Isobars, Synoptic Isobars, Model Spread, Wave Confidence, Lightning. The tooltip then reads: Unavailable in climatological mode (departure >7 days). Requires real-time forecast or GRIB data. - Hover over each overlay name to read its descriptive tooltip.
The Weather overlays
Overview (details in the notes below):
| Overlay | What it shows | When to use it | Prerequisite |
|---|---|---|---|
| Wind Roses | Seasonal wind patterns by ocean zone (pilot charts) | Long-haul planning, choosing a season | None (climatology) |
| Ocean Zones | 12 named ocean zones with boundaries (trade winds, westerlies, monsoons) | Understanding global wind regimes | None |
| Gale Zones | Areas with high gale probability for the selected month | Avoiding gale-prone areas by month | None (depends on selected month) |
| Visibility | Visibility / fog forecast | Approaches, coastal nav in poor visibility | Real-time forecast / GRIB |
| Isobars | Pressure isobar lines, H/L centers and fronts (local) | Reading pressure around your position | Real-time forecast / GRIB |
| Synoptic Isobars | Full-map pressure isobars with H/L centers and fronts | Big-picture synoptic view | Real-time forecast / GRIB; zoom 3-8 |
| Model Spread | Multi-model forecast uncertainty (GFS, ECMWF, ICON…) | Gauging forecast reliability | Real-time forecast / GRIB |
| Split View | Side-by-side weather comparison | Compare wind vs waves, or two dates | None (depends on loaded data) |
| Satellite | Satellite infrared imagery & precipitation radar | Spotting squalls, fronts, storm cells | Connection (RainViewer) |
| Lightning | Thunderstorm risk from CAPE convective energy | Anticipating storms and squalls | Real-time forecast / GRIB; zoom ≥ 5 |
| Wave Confidence | Wave forecast confidence (ECMWF WAM, GFS Wave, DWD GWAM) | Gauging wave forecast reliability | Real-time forecast / GRIB |
| Seasonal Forecast | SEAS5 — probabilistic wind anomaly up to 6 months ahead | Choosing a seasonal window | Connection (SEAS5 data) |
| Climate indices | ENSO / NAO / AMO / Atlantic hurricane outlook (NOAA, monthly) | Yearly climate context | Connection (NOAA) |
Wind Roses
What it does: shows seasonal wind patterns by ocean zone, drawn from pilot charts (climatology). Ideal for planning a passage by season. How to use it: 1. On the Weather tab, click Wind Roses. 2. Wind roses appear over the ocean zones. Options & settings: overlay on/off. Tips & limits: climatological data, available even without a real-time forecast. They depend on the month selected in the app.
Ocean Zones
What it does: outlines 12 named ocean zones (trade winds, westerlies, monsoons…) with their boundaries, to understand global wind regimes. How to use it: 1. On the Weather tab, click Ocean Zones. 2. Zone boundaries and names are displayed. Options & settings: overlay on/off. Tips & limits: climatological reference view, no forecast prerequisite.
Gale Zones
What it does: highlights areas with a high probability of gales for the selected month. How to use it: 1. On the Weather tab, click Gale Zones. 2. Risk areas appear in red. Options & settings: overlay on/off. Tips & limits: depends on the month chosen in the app; cross-check with your departure window.
Visibility
What it does: shows the visibility / fog forecast (mist, dense fog, etc.). How to use it: 1. On the Weather tab, click Visibility. 2. The chart is tinted by visibility class (dense fog <200 m, fog <1 km, mist <5 km, haze <10 km, good >10 km). Options & settings: overlay on/off; legend by class. Tips & limits: requires a real-time forecast or GRIB; greyed out in climatological mode.
Isobars
What it does: draws isobar lines, high (H) and low (L) pressure centers and atmospheric fronts around the displayed area. How to use it: 1. On the Weather tab, click Isobars. 2. Isobars and H/L centers appear. Options & settings: overlay on/off. Tips & limits: requires a real-time forecast or GRIB; greyed out in climatological mode. For a wider view, use Synoptic Isobars instead.
Synoptic Isobars
What it does: displays pressure isobars across the whole map, with H/L centers and fronts, for a synoptic big-picture read. How to use it: 1. On the Weather tab, click Synoptic Isobars. 2. The pressure field covers the entire map. Options & settings: overlay on/off. Tips & limits: requires a real-time forecast or GRIB; designed for zoom 3 to 8 (wide view). Greyed out in climatological mode.
Model Spread
What it does: visualizes forecast uncertainty by comparing several models (GFS, ECMWF, ICON…). The larger the spread, the less reliable the forecast. How to use it: 1. On the Weather tab, click Model Spread. 2. Areas where models diverge are displayed. Options & settings: overlay on/off. Tips & limits: requires a real-time forecast or GRIB; greyed out in climatological mode. A large spread flags a forecast to treat with caution.
Split View
What it does: compares two weather views side by side (e.g. wind vs waves, or two different dates) on a split screen. How to use it: 1. On the Weather tab, click Split View. 2. The map splits to show two weather states in parallel. Options & settings: overlay on/off. Tips & limits: handy to quickly contrast two parameters or two time steps.
Satellite
What it does: overlays satellite infrared imagery and precipitation radar (RainViewer) to spot squalls, fronts and storm cells. How to use it: 1. On the Weather tab, click Satellite. 2. Infrared imagery and/or radar appear. Options & settings: Infrared, Radar and Forecast modes; Opacity control; imagery Refresh button. Tips & limits: requires a connection (RainViewer source). A message appears if IR data is momentarily unavailable.
Lightning
What it does: estimates thunderstorm risk from convective energy (CAPE) — useful to anticipate squalls and storms. How to use it: 1. On the Weather tab, click Lightning. 2. The chart is coloured by risk level (low, moderate, high, extreme). Options & settings: overlay on/off; legend by level. Tips & limits: requires a real-time forecast or GRIB; zoom ≥ 5 is required for display (a reminder shows when the overlay is active). Greyed out in climatological mode.
Wave Confidence
What it does: indicates wave forecast confidence by comparing the ECMWF WAM, GFS Wave and DWD GWAM models. How to use it: 1. On the Weather tab, click Wave Confidence. 2. Areas where models agree (high confidence) or diverge (low confidence) are shown. Options & settings: overlay on/off. Tips & limits: requires a real-time forecast or GRIB; greyed out in climatological mode.
Seasonal Forecast
What it does: shows the SEAS5 seasonal forecast — a probabilistic wind anomaly up to 6 months ahead, to help choose a seasonal departure window. How to use it: 1. On the Weather tab, click Seasonal Forecast. 2. The map is coloured by tercile probability (below normal / near normal / above normal). Options & settings: variables available depending on data (wind, SST, pressure); AI analysis available on the active route (LLM briefing, requires at least 2 waypoints). Tips & limits: requires a connection to load SEAS5 data. The colour legend corresponds to tercile probability. Issue date is displayed.
Climate indices
What it does: provides large-scale climate context — ENSO / NAO / AMO and the Atlantic hurricane outlook (NOAA, monthly update). How to use it: 1. On the Weather tab, click Climate indices. 2. Index values and, where relevant, the reference zone are displayed. Options & settings: Show reference zone on map option; update date shown; open source data. Tips & limits: requires a connection (NOAA). Updated monthly — use it as climate backdrop, not as a short-term forecast.