fogbanks

Fogbanks are large, contiguous areas of fog that reduce surface visibility and can persist for hours or days. They are most common near coastlines and over shallow seas, where patches of fog can combine into a continuous sheet that covers tens to hundreds of square kilometers.

They form when air near the surface becomes saturated and cools to below its dew point, causing condensation. This can occur through nocturnal radiative cooling of land (radiation fog), horizontal movement of warm, moist air over a cooler surface (advection fog), or moisture rising from mild ocean water into cold air (steam fog). Sea fog is a form that develops and persists over water and can coalesce into fog banks offshore.

Fog banks are influenced by wind and currents. Light or no wind promotes thick, stable fog; moderate winds may thin or break it up and move the fog bank; strong winds disperse it quickly. Fog banks can travel with the prevailing wind and surface currents, sometimes presenting a moving hazard to vessels and aircraft.

Impacts include visibility reduction that affects transportation, scheduling, and safety; ships may face collision risk; runways may close; and there can be economic costs for fishing, shipping, and tourism.

Forecasting and observation rely on surface and air temperatures, dew point, humidity, wind, and cloud cover. Sensors measure visibility and dew point; satellite imagery detects fog; meteorological reports (METAR) provide current visibility. Forecasting can warn of dense fog and guide operations.