Module 13 - Meteorology
Sea Fog
Coastal sea fog is commonly advection fog: relatively warm moist air passes over a cooler sea surface and is cooled to its dew point. Around the UK this can affect windward coasts when the airflow crosses colder water.
The location, movement and persistence depend on wind direction and strength, sea and land temperature, moisture and topography. A small temperature–dew-point spread or low stratus supports concern but does not guarantee fog at the yacht.
Use official visibility forecasts, warnings and nearby observations alongside onboard evidence. Before entry, prepare the restricted-visibility plan: safe speed, engines as appropriate, navigation lights, sound signals, radar and AIS used within their limits, extra lookout, position evidence and an abort or holding option.
| Evidence | What it supports | Limit |
|---|---|---|
| Warm moist air over colder sea | Advection-fog set-up | Does not fix exact location or onset |
| Nearby visibility worsening | Fog or low cloud approaching the route | Station may not represent the yacht |
| Low stratus over water | Low-level saturation nearby | Can lift, lower or remain local |
| Wind | Transport and modification | Does not guarantee clearing |
Optional quick check
Section 11 of 15
Which condition most directly supports advection sea-fog formation?
Sources and factual review
Reviewed 20 August 2026 - Compass Revision editorial review.
Continue studying Meteorology
This public lesson is part of Revision Module 13. Full revision access adds the guided Learn, Practise and Test flow, flashcards and revision progress.