NIMBOSTRATUS CLOUD (NS)
Nimbostratus symbol is:
Stratus(ST)
The word 'Stratus' comes from the Latin word 'layer'. The symbol for stratus is:
Stratus hovers just above the ground below 2000 meters. There formation consists of a horizontal gray layer that spreads over a large area.
There are three types of Stratus Cloud; known fog and mist. The difference between fog and stratus is mainly the fog cloud is closer to the ground then stratus, and the difference between mist and stratus is, stratus is much thicker.
Stratus -and fog- most commonly form in September and October. This because the longer nights, and moist air that comes after summer. This all helps form Stratus and fog. Stratus is a unique type of cloud because it forms on -unlike other clouds- the ground. Stratus cloud dose not bring rain but can leave a kind of dew or mist behind.
Fog can form within an hour or until morning. Especially when the skies are blue and light winds, causing the mercury to drop more quickly.
The Pacific Northeast coastline, has one of the most foggiest weather,including New England and over the Central Appalachian mountains. The Rocky mountains and the Southwest Desert have the least common fog
Early morning fog may rise to form a Stratus. All together there are for different types of fog:
Radiation Fog: is formed the same way dew is; on long night the ground cools quickly by radiation (hence the name). As the temperature drops the humidity rises. Light winds are also required for they gently mixes the moist air with the cool air near the ground. More stronger winds can mix the dry air from the ground, with the warmer air from above. This keeps the air near the surface from becoming saturated.
Radiation Fog is most commonly seen in Autumn, especially around river valley's. Cold air from above falls to the bottom, this provides the cool air above. The water from the river and streams provides the water vapor needed to increase the relative humidity and evaporation. These types of fog are commonly known as 'Valley Fogs'.
To forecast Radiation fog there are certain guidelines to follow such as; if the temperature is about 14 F below the temperature at sunset, also if the wind speed is less than 5 knots (or 9 kilometers), then there is a good chance Radiation fog will form.
Advection Fog: Advection means 'blown horizontally'. Advection Fog most commonly forms off the coast of California near to San Fransisco. This is because when the warm moist air blows over the Pacific, it can cause an exchange with the surface. This makes the humidity increase casing Advection Fog to form.
Advection Fog can also appear off the East coast, also off the coast of Japan. These fogs can form at all times of the year and can last for more than a week.
Advection Fog can occur when warm air flows from the water to cooler lands, making fog common along the coast of the Gulf of Mexico. During fall and winter the saturation of the air happen when the moist air flows from the Gulf over to cooler lands. This processes also occurs in New England and London.
Evaporation fogs: are sometimes called 'Frontal Fogs'. Evaporation Fog can often occur after a hot shower when everything 'fogs up', this happens when the hot water from the shower evaporates into the air this makes it rather humid eventually becoming saturated and forming fog.
Evaporation fog can occur around the area of warm fronts, which is why it is also called Frontal Fogs. Frontal Fogs form when rainfall evaporates into warm air and mixes with the cold air near the ground. Because of this Frontal Fogs can only occur after long periods of rain fall, for it takes 5 times for the water to evaporate causing the air to become saturated. For example you cannot 'fog up' the bathroom by taking a short shower.
Evaporation Fog can also form over lakes, after much colder air moves over warmer air. The colder air has less vapor pressure then that over water causes evaporation to become more rapid. This rapid evaporation saturates the air above even more quicker. After evaporation the condensation would start warming the air. The warm air would rise and mix with the cool air above, causing both to become saturated which in turn leads to more fog to form.
When Evaporation Fog forms over a lake it can easily be mistaken as steam rising from the water. Because of this Evaporation Fog is sometimes called 'Steam Fog'. Steam Fog is most common in late autumn and early winter, forming in cold areas for example: the northern mid-latitude regions. Steam fog is common when when cold air blows over unfrozen waters.
Upslope Fog: As air rises over a mountain barrier, air expands and cools making the humidity level rise. When the air becomes saturated Upslope Fog will form. Upslope Fog is common around the Appalachian Highlands such as the Smoky Mountains.
Upslope forms best when the air flowing upward is cold, so it dose not required much lifting before saturation occurs.
