ABSTRACT. – Meteorological Ground Fog Forecast Tools. Fog represents a severe obstacle for land and air traffic; the phenomenon is occurring when the visibility of the atmosphere, near the Earth's surface, becomes less than 1 kilometer. Discrimination between very low stratus clouds and fog are difficult to make. Fog develops when the air at ground level is cooled enough to cause saturation (relative humidity equals 100%) and its forecast is very difficult.
Key-words: Meteorological Ground, visibility, relative humidity