This is a pre-passage source and decision desk, not a current forecast or clearance to depart. The map is centred approximately on the area, not on your route or a forecast-zone boundary.
Sea-area bulletins and archipelago or fjord conditions have different scales. In season, check ice and sea-level products; in narrow passages also examine current and visibility, not only mean wind.
1. Primary sources
Open current bulletins and warnings for every sea area on the route. These links are starting points, not a promise that each covers the whole location; if unsure, identify the issuer through WMO–IMO.
2. Route and local effects
Check wind, current and the transition between Baltic and North Sea areas.
Danish straits connect Baltic and North Sea waters through narrow, tidal and heavily trafficked passages.
Read DMI named sea areas and neighbouring SMHI where relevant; add local current and traffic notices before deciding a strait transit.
How to use this source set
Start with the warning, then the marine text for the exact named area. If the route crosses a zone boundary, obtain both bulletins. Note issue and valid times, wind units and the meaning of wave height. Where a link opens an agency portal, navigate to its current marine product; a homepage is not itself a forecast.
Compare with an exposed station or buoy if available. Check its position and observation time: a sheltered station does not overturn a warning for an open channel. If a bulletin is missing or stale, identify the issuing service via WMO–IMO and defer the decision until current information is available.
Before-passage check
- Mark departure, exposed legs, arrival and feasible diversions; find the responsible named marine areas for each.
- Check warnings, issue and valid times; assess conditions when you expect to reach each leg, not only at departure.
- Compare wind and gusts, waves and swell, visibility, thunderstorms and local effects; do not infer a strait from a sheltered harbour.
- Compare recent observations where available, noting their time and exposure; a mismatch calls for another check.
- Set the next bulletin check, a reassessment trigger, an alternative and a backup communication channel.
Model map — optional
Windy is a third-party model display, not the issuer of official warnings. Choose a layer and check its valid hour and model run. Nothing loads until you click.
Without JavaScript, open the map separately.
If connectivity fails
Before departure, save the current official text bulletin and warning with issue time. Arrange another way to receive updates, such as an appropriate coastal broadcast, NAVTEX or satellite channel. A saved map cannot replace new warnings.
How to choose weather tools · All sailing areas
Scope: Source list assembled 25 September 2026; check its freshness and coverage before use. This public area guide is not a current personalised forecast, navigational notice service or safety verdict. Personalised forecasts with AI and experts are in closed testing; public booking is not open. The skipper makes the decision.
Name the Sound or Belt, not just Denmark
An Øresund, Great Belt or Little Belt itinerary should identify its actual strait, exposed connections and arrival shore before selecting DMI's sea-area product. Those passages are not interchangeable with an open Baltic crossing. Add a neighbouring national forecast where the route needs it and keep visibility and traffic context visible. A Danish country-wide warning or a Copenhagen city forecast cannot represent all strait conditions.
- DMI water-level interpretation — Measured versus forecast level, vertical reference and limits of automated curves.
- SMHI sea-weather services — Shipping/sea-coast forecasts, coastal observations, water-level/wave and ice products.
Do not call every strait flow a tidal stream
Water exchange and weather-driven flow must not be reduced to a high-water timetable. DMI's water-level guidance separates measured and forecast curves and specifies reference systems; a level curve is not itself a current measurement. Use an applicable current product for the chosen passage and preserve its model/observation status. A global current field may offer context, but does not establish local slack or the force through a narrow entrance.
- DMI water-level interpretation
- BSH modelled surface currents — Hourly operational model currents include tidal and wind-driven components; inspect date.
Compare the transit and the onward exposure
For a Baltic-to-Kattegat scenario, assess the strait ETA separately from the next open-water leg and destination. If wind or water-level changes affect progress, rebuild both timelines instead of checking only the strait itself. Reconsider when visibility no longer supports the intended watchkeeping plan, the current evidence is stale or the arrival constraint is missed. Local chart, bridge and authority information remain separate prerequisites.
- DMI water-level interpretation
- RYA passage planning — Practitioner guidance on contingency, tides, vessel and crew constraints.
Editorial review of this material: 27 September 2026. This date concerns the page content; check current forecast issue times and validity at the original sources.