Use named KNMI coastal sectors and a separate water-level/approach check.
Forecast sectors and coverage
KNMI coastal products name sectors including IJmuiden, Texel, Rottum, Harlingen and Delfzijl. Trace your leg against the current sector definitions; a Wadden approach is not automatically covered by one offshore North Sea chart.
Weather-sensitive legs
Treat an offshore coastal leg, inlet and drying/shallow-water approach separately. Wind against tidal flow and swell at an inlet must be assessed with current local publications; no passability or under-keel clearance is calculated here.
Observations, sea state and reassessment
RWS Waterinfo can provide relevant water observations. Confirm station, datum and forecast versus observation; an open-sea wave value is not the wave condition over a changing shallow approach.
Worked planning scenario — not a live forecast
Compare departure options at both the coastal leg and inlet ETA. If the arrival depends on a verified tidal window, hold that constraint explicitly rather than selecting the lowest wind from the model comparison.
Official products by task
- KNMI coastal waters — Named Dutch coastal, estuary and lake sectors; issue and validity are shown at the issuer.
- Rijkswaterstaat Waterinfo — Water levels and available water observations; check station, units and datum before comparison.
Sector names help you locate the issuing product; they are not an automatic route-coverage match. Open the current issue and check boundaries, issue time and validity. This page does not display current warnings; an unavailable product does not mean no hazard.
Countries & territories
- Netherlands
Distinguish North Sea/Wadden, inland lakes and Zeeland waterways before choosing data.
Map orientation
The approximate map centre is not an approach waypoint, track, depth survey or forecast-zone boundary. The third-party map loads only on request.
Build your passage brief
Bring your route, leg timings, vessel and crew profile, checked sources and reassessment triggers into the brief. Personal AI analysis and expert review are available to invited closed-test participants; a port page does not extend the calculation service’s coverage.
A Sailing Weather editorial guide to local conditions, practical passage preparation and marine-weather sources. Source and structure review: 27 September 2026. For a specific passage, check current issues, validity and forecast coverage. The skipper retains the final decision and responsibility.
An offshore hour is not an inlet slot
Divide a North Sea-to-Wadden itinerary into the sea leg, the selected island inlet and the inside-water destination. The KNMI coastal names help choose weather text, but do not identify a navigable channel or its current depth. Assess wave access and wind against the local stream at the inlet ETA, using current hydrographic and harbour information. A quiet forecast inside the islands cannot be used backwards to clear the sea-facing entrance.
- KNMI coastal waters, lakes and estuaries — Named Dutch sectors including IJsselmeer and Marken; read actual issue/validity.
- Rijkswaterstaat Waterinfo — Water observations and forecasts; parameter, station and datum must be checked. Direct product verification is limited; obtain the current issue from the issuer.
Choose a water observation, not just a map pin
In Waterinfo, confirm the parameter and whether it is an observation or prediction. A water-level series, wave series and current field answer different questions; their station locations need not coincide. Check the reference system against the chart before any depth arithmetic. Avoid filling an unavailable inlet observation with a distant station merely to make the brief look complete.
Plan a genuinely different fallback
For an island arrival, compare the nominal ETA with reduced speed, changed stream timing and an unplanned wait. Reassess when the entrance wave direction changes or a local update conflicts with the broad coastal picture. A fallback requiring another unverified inlet is not automatically an improvement. Keep waiting offshore and returning to the last confirmed harbour as separate options to be judged from the actual conditions and vessel endurance.
- KNMI coastal waters, lakes and estuaries
- 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.