Land (Radiation) Fog

Clear nights with little wind. Damp warm air radiates off as the ground cools at night condensation takes place. Fog forms first over valleys, water, and damp vegetation

Thickest around dawn when the air temperature is at its lowest. (Heat from sun usually disperses this type of fog.

Usually occurs in settled weather in autumn/winter. Land cools down quickly at night. Moisture condenses and forms fog over land which will drift out to sea on the land breeze.

Sea (Advection) Fog

Tropical maritime -warm moist wind blowing over cold sea air cools and water vapour condenses to form fog.

Force 5/6 winds will lift the fog to form low stratus cloud. Sun tens to thicken the fog by warming the air further

This occurs when warm moist air blows over a colder sea.  It is usually associated with the warm S or SW winds of a is most common in spring when sea

temperature is at its lowest.

Action to take in low visibility
  • Reduce Speed (Rule 6)
  • Close Watertight Doors
  • Post Extra Look-Out
  • Take a Fix
  • Man the Radar
  • Make sound Signals (Sound signals)
  • Turn on Navigation Lights
  • Reduce deck Noise
  • Prepare to anchor