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.
National forecast responsibility changes quickly across these coasts and straits. Check the exact marine zone, tropical-system alerts where applicable, visibility and the latest local port or traffic notices.
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
Island passages need national marine warnings and a separate tropical-cyclone check.
The Ryukyu chain consists of open island gaps, while the Japanese main-island forecast may refer to a different sea area.
Select the JMA marine area for each island gap and any typhoon warning. Compare swell at the destination entrance with open-sea conditions.
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.
Different warnings answer different questions
JMA provides marine warnings/forecasts and tropical-cyclone information as separate products. For an Okinawa–Miyako–Yaeyama itinerary, verify the sea area for each open island gap rather than reusing a mainland or municipal weather page. Coastal weather warnings and offshore marine forecasts are not identical coverage. Keep original area names, issue and valid times in the brief, and retrieve the latest product rather than relying on a cached warning display.
- Japan Meteorological Agency marine product directory — Marine warnings, forecasts, tropical cyclones and observations; verify specific area Direct product verification is limited; obtain the current issue from the issuer.
Naha's safety desk is local, not archipelago-wide
The Coast Guard's Naha desk links port notices, typhoon-related recommendations, Okinawa marine information, reef-current information and tide services. Use each according to its stated locality; Naha's tide record cannot supply every Ryukyu harbour's current phase. These operational notices are different from a model forecast and may affect access regardless of weather-map colours. Obtain the equivalent current authority information for other destination ports.
- Japan Coast Guard Naha marine-safety desk — Naha port notices, Okinawa marine information and tide links; not every Ryukyu port Direct product verification is limited; obtain the current issue from the issuer.
Plan the later arrival and next update
For a long island gap, compare departure options at the exposed midpoint and destination approach, including incoming swell, daylight and crew endurance. Do not equate distance from a cyclone centre with a complete sea-state assessment. Record the next warning-update channel and any unresolved local-current or harbour task. This article supplies no reef-entry instruction, cyclone refuge guarantee or automatic clearance to depart.
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.