Fooks on Fog

Our meteorological correspondent shares his reflections on fog - from a fog bank

Tim F: 20/08/2026

Five days ago, Belle Colombe made a glorious 100nm crossing of the Cabot Strait, from the SW corner of Newfoundland (NFL) to the Bras d’Or Lakes of Nova Scotia (NS), in bright sunshine with wonderful visibility and a delightful sailing breeze. Today we have spent the day motoring from the southern exit of the Lakes to the south coast in NS in thick fog combined with a stiff, but warm, F5-6 on the nose. Indeed, the first we were aware of today’s chosen anchorage was when we saw waves breaking on rocks no more than a boat’s length away.

Fog has been such a regular, and significant, feature of this voyage it seemed appropriate to reflect on why every sailor in this part of the world should expect at least part of every journey to be fog-bound.

Fog is simply a form of cloud that occurs at sea level. By definition, it reduces the horizontal visibility to less than 1000m or five cables. (Mist refers to visibility from 1-5km). The principal culprit is advection fog. Warm, moisture-laden Atlantic air moves across much colder water and is chilled from below until its moisture condenses – the dew point.

The dew point can vary dramatically. Today it was 20°C and the sea surface temperature was 17°C; when we were in fog in the Labrador Sea it was 6°C and the sea 4°C.

Around NFL and NS, nature’s fog factory is particularly effective because warm Gulf Stream water running north and east up from the Gulf of Mexico and across the North Atlantic lies alongside the cold, south-flowing Labrador Current. The Grand Banks, which lie to the east of NFL, are consequently among the foggiest places on Earth - and certainly the foggiest part of Canada - with poor visibility on as many as 80% of summer days.

Ice intensifies the effect. At the eastern entrance to Prins Christian Sund we watched a colossal iceberg apparently manufacture its own foggy weather: moist air passing over the berg and its surrounding near-freezing water was cooled sufficiently to produce a local shroud of fog.

Fog can have remarkably sharp edges. These fog banks form where the necessary combination of temperature and humidity exists on one side of a boundary - perhaps a change in sea temperature or air mass - but not the other. At times, Belle Colombe sailed from sunshine into near-zero visibility and back again within minutes.

Unlike today, we have often found fog dispersing as we entered a harbour such as L’Anse aux Meadows; it is a very welcome phenomenon especially where the Navionics charts have been so inaccurate. Land warms much faster than the sea; air moving ashore is heated from below, lowering its relative humidity and evaporating the fog droplets. Local topography and shelter from the moist maritime airflow can reinforce the effect.

It is often assumed that wind disperses fog, but in these waters the relationship is more complicated. As has occurred today, strong winds frequently accompany fog rather than clear it, maintaining the turbulent mixing of warm and cold air masses that sustains it. Today, the fog has persisted throughout the day and shows no sign of disappearing as night draws in.

The danger fog presents to a yachtsman needs little explanation. The Grand Banks’ combination of fog and ice has challenged mariners for centuries. The loss of the SS Florizel off Cape Race in 1918 - a passenger liner that ran aground in heavy fog and broke apart, killing more than 80 people - remains one of NFL’s most enduring maritime tragedies and a stark example of how completely fog can erase the coastline.

Although thick fog in the busy waters of the Solent is quite rightly a cause of collision anxiety, we have come across so few vessels of any description during this journey that our concerns have been more often focussed on avoiding rocks, lobster pots or ice.

However, when visibility deteriorates significantly, we have now become used to switching on our radar (good for land, ships, icebergs and large growlers), looking for AIS (Automatic Identification System) signals from other vessels on the chartplotter, blasting out a signal every two minutes if we think there might be non-AIS transmitting fishing vessels about and keeping ‘watch’ with both eyes and ears. Fog horns on shore are common around the coast of NFL and NS and we have probably heard them as much as seen them.

As visitors to these waters, the frequency and intensity of fog has been, at times, unsettling, but the locals are well accustomed to this: Newfoundlanders have told us that fog is not seen as an exceptional event but as part of daily life. People plan around it, speak of it with pragmatic familiarity, and judge conditions not by whether fog is present, but by how thick it is and how it behaves.

For us, to be in dense fog at sea, with unknown obstacles ahead and a loss of all points of reference, remains an uniquely isolating experience. As the famous Nova Scotian sailor, Joshua Slocum, remarked in his classic book Sailing Alone Around the World, “I was in a world of fog, shut off from the universe.”