Separate the Archipelago Sea, Gulf of Finland and northern Baltic coasts; retain the sea-level reference and season.
Choose the Finnish water system first
An island week west of Turku, a Gulf of Finland crossing and a northern Bothnian coastal passage have different exposure and source needs. Do not stretch an Archipelago Sea forecast across all of Finland. Mark sheltered channels, open crossings and the final entrance separately. Inland lakes are another planning category: coastal sea level, marine waves and lake access information cannot simply be exchanged because the same yacht is used.
Use the marine issue and explicit warnings
FMI provides a shipping forecast by sea area and a marine map with observations and forecasts. Select the actual marine district and inspect its current issue and validity; the service describes an automated shipping forecast, so do not imply that every displayed value was individually signed off by a meteorologist. Check warnings separately and keep neighbouring-country products for cross-border legs. A Turku city forecast cannot replace the outer-archipelago forecast.
Water level is not a generic tide correction
FMI shows both N2000 and theoretical mean-water values. Copy the reference with the number, then compare it with the chart and fairway information actually carried aboard. Low astronomical tide does not mean constant depth: weather-driven level changes still matter. A station near Turku is evidence for that station, not proof of clearance in a remote channel. This guide does not calculate under-keel clearance or supply a navigable route.
Treat an exposed gap as its own weather leg
Compare the wind's approach direction, available fetch and arrival shore for every open section. A short distance on the chart can still mean a demanding crossing between protected channels. Check mean wind, gusts and visibility independently, and do not treat significant wave height as the largest possible wave. If an inside alternative is proposed, test its charted restrictions and navigation workload before counting it as the backup.
Ice, commercial traffic and the next review
Use a dated FMI ice chart and current port information when the season requires it; the presence of a harbour on a summer chart is not evidence of winter accessibility. In busy approaches read Fintraffic's current VTS guidance and identify requirements applicable to the yacht rather than copying merchant-ship procedures. Finish the brief with an update time, a confirmed waiting location and a cold-water/communications plan. The skipper remains responsible for departure and navigation.
Official products by task
- FMI shipping forecast — Automated marine forecast divided into sea areas; the current page states six updates daily. Read issue/validity and the relevant sector, not a Turku city forecast.
- FMI marine observations and forecast map — Choose marine variables and a station/valid hour. The map distinguishes mean wind/gust, water-level references, waves and seasonal ice; a displayed grid is not charted passage clearance.
- FMI sea-level observations and forecasts — Station products include Turku and separate N2000 from theoretical mean water. A remote station or an ensemble interval cannot certify a particular shallow channel.
- FMI Baltic ice chart and report — Seasonal ice information; check the actual latest issue, geographic detail and associated restrictions. An ice chart is not an approved leisure-craft route.
- Fintraffic vessel traffic services — Official VTS participation and listening-watch guidance. Determine applicability to the yacht; do not copy merchant-vessel or pilotage requirements indiscriminately.
Waters and onward passages
- Finnish Archipelago Sea
Pair the sea-area bulletin with local channel and sea-level information.
- Gulf of Finland
Use the correct national forecast and watch visibility, sea level and ice when relevant.
- Baltic Sea
A Baltic overview should lead to the right national sea sector and water-level product.
Departure ports and bases
- Turku
Separate the Aura River or actual marina departure from the outer Archipelago Sea and any Åland crossing.
Prepare a passage brief
Bring route timings, vessel and crew profile together with checked sources and reassessment triggers. Personal AI analysis and expert review are in invitation-only closed testing. An editorial geographic page does not extend the calculation service’s actual coverage.