What are weather fronts?
When large masses of warm air and cold air meet, they don’t mix together, but rather they form what is called a weather “front.” You can picture this as a kind of transitory zone, between two different air types on the Earth’s surface. This front is usually hundreds of miles long and triggers a change in the weather; more often than not, it can cause turbulence such as rain or wind storms.
Certain fronts can cause storms or hurricanes which can tear through nearby cities and villages. Fronts usually move across the Earth’s surface for a series of days, and the direction of movement is often dictated by high winds such as Jet Streams, though landforms like mountains can influence the path of the weather front, too.
When locating a weather front on a map, it is useful to look for patterns such as sharp temperature changes over relatively short distances, changes in the amount of moisture in the air (also known as dew point), a shift in the direction of the wind, low-pressure troughs and other pressure changes, as well as clouds and precipitation patterns.
There are four main types of weather front: a Cold Front, Warm Front, Occluded Front, and, last but not least, a Stationary Front, which is the type we will be focusing on today.
What is a Stationary Front?
A Stationary Front - as its name gives away - is formed when a cold or warm front stops moving. This is a result of the two masses of air pushing against each other, with neither being able to shift the other. This front may last for days, and winds blowing parallel to the front can lock it in place.
Because a Stationary Front is where two types of air masses meet, there is often a contrast in air temperature and wind on either side of the front, which can in turn produce multiple types of weather.
When the wind changes direction, this may prompt the front to start moving again, and it will become either cold or warm. Alternatively, the front will break apart.
What symbols depict a Stationary Front?
On a weather map fronts are depicted in various colors and shapes. Because a stationary front involves two air masses, a stationary front is illustrated using a combination of the symbols used for warm and cold fronts: a string of interlocked red semicircles (warm front) and blue triangles (cold front), each pointing against each other to convey their opposition to each other.
When Stationary Fronts shrink in size, they degenerate into a narrow zone where the wind changes direction significantly over a short distance, and these are then called ‘Shearlines’. On a weather map, these are depicted by a line of red dots and dashes. Shearlines most commonly take place over the open ocean.
What weather occurs at a Stationary Front?
While known as a “Stationary” front, the weather this kind of front brings is anything but stationary, and you’ll often find winds blowing parallel to the front, as we mentioned previously, along with distinct differences in temperature on either side of the front, which acts of a sort of barrier between the approaching warm front, where you’ll find higher temperatures, and the approaching cold front, where temperatures will be significantly lower.
Overcast and dreary weather is commonplace when a Stationary Front occurs. This may be characterized by light - but persistent - precipitation that continues for days at a time, though it largely depends on the level of moisture in the air. Snow and fog may also occur.
While the weather conditions mentioned above are relatively mild and expectant, occasionally a Stationary Front can lead to freak weather events, too. Thunderstorms or heavy rain may be shafted down the front, and, when there are high levels of moisture in the air, heavy precipitation can lead to flooding within the surrounding region which can wreak havoc for residents.
Powerful, straight-line winds, also known as Derechos - the Spanish word for direct - may develop due to strong downdrafts along the border of the front and these can reach up to 160 km/h. They often accompany thunderstorms, too.
In North America, Derechos mostly develop in Spring and Summer months east of the Rockies mountain range, and, at their most powerful, they can be fatal for humans - particularly those living in woodland areas - as Derechos have been known to flatten entire tracts of timber.
Conclusion and summary
Though stationary fronts are discussed less frequently than warm or cold ones, they are still important to understand as they happen relatively frequently. The bottom line when it comes to Stationary Fronts is that the cold and warm air masses push against each other so the front becomes stationary, as one air mass cannot override the other.
This front is usually characterized by distinct differences in temperature on either side of the front, with warmer temperatures on the approaching warm front and cooler temperatures on the approaching cold front.
Generally speaking, weather conditions generated by his kind of front are light precipitation that can last for days, and occasionally fog and snow.
On a weather map, a stationary front is shown as alternating red semicircles and blue triangles which point in opposite directions to represent the warm air mass and the cool air mass.
Occasionally more extreme weather occurs as a result of stationary fronts, and these usually cause thunderstorms, which can occasionally cause Derechos to shunt off of the jet stream and create powerful windstorms that tear through anything in their path.