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.
A long high-latitude or transoceanic leg crosses forecast responsibilities and update cycles. Separate meteorology from current chart, ice, port and navigation warnings, and plan a dependable offshore receiving channel.
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
The source and warning authority changes across a multi-week route.
A South Atlantic crossing can span multiple METAREAs over many forecast updates, with limited diversion options.
Identify the issuers for the whole route, not just departure; compare synoptic warnings, swell and communication windows, and do not use a single model run as a passage clearance.
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.
A crossing is a sequence of issuing areas
For a Brazil-to-southern-Africa or another South Atlantic scenario, map the actual ocean track to the relevant METAREA issuers rather than assuming the departure country serves the whole voyage. CHM's METAREA V context applies within its coverage; onward areas require their own products. Keep departure coast, ocean monitoring and landfall preparation as separate source groups. A named ocean does not imply one warning authority or one forecast update.
- WMO–IMO marine warning directory — METAREA issuer discovery; products may be delayed, national issuer remains authoritative.
- Brazilian Navy CHM metocean bulletin — METAREA V synoptic, wind/wave and warning context; inspect attached issue.
Long-range precision should be visibly limited
Place forecast support on the time-position schedule and mark where arrival lies beyond useful detail. Compare alternative low-pressure developments, swell direction and slower progress rather than extending a single deterministic field through a multi-week trip. The brief should distinguish current evidence, near-term expectations and unresolved later stages. A climatological current or wind belt can support planning context but cannot fix today's boundary or the next week's actual route.
Define the missed-update scenario before departure
Confirm which warning text and forecast can actually reach the yacht offshore, then record a backup and next update opportunity. Reassess if progress, communications or the synoptic pattern diverges from the plan. Remote islands or an alternative continental landfall need fresh local approach information; they are not automatically available shelters. The skipper needs a new position-based brief, not repeated reassurance from the departure summary after its detailed horizon ends.
- WMO–IMO marine warning directory
- 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.