Havsprognoser

Havsprognoser are marine weather forecasts for sea areas and coastal waters that inform mariners and coastal authorities about expected sea conditions over upcoming hours and days. The term is commonly used in Sweden and other Nordic countries to describe forecasts that cover winds, waves, currents, visibility, and related hazards at sea.

Typical contents include wind speed and direction, significant wave height and wave period, swell direction, surface currents, sea-surface temperature, visibility, precipitation, and ice conditions where relevant. In hazard situations, forecasts may include warnings for gale or storm-force winds, high seas, and coastal flooding or storm surge.

Production relies on numerical weather prediction models, supported by observations from buoys, ships, coastal networks, radar, and satellites. Ocean-wave models (for example, SWAN or WAM) translate wind fields into wave fields. Forecast horizons commonly range from 24 to 72 hours, with longer-range projections for certain variables limited by uncertainty.

Forecasts are disseminated by national meteorological services and coastal authorities via websites, apps, and marine-advisory bulletins. They are used by shipping companies, fishing fleets, offshore energy operations, search-and-rescue services, and recreational mariners.

Limitations include model uncertainties, especially in complex coastal geometry, rapid weather changes, and near-shore conditions. Users are advised to consult official warnings and update forecasts regularly before planning activities at sea.