With the weather constantly changing, a lot of us like to tune into the weather forecasts again and again in order to try and have some idea of what to expect.
Whether it’s sunshine or showers, most of the terms used in the weather forecasts are fairly easy to understand. However, you may have noticed the terms “warm front” and “cold front” coming up regularly and not known what they are.
What do they mean? What is the difference between the two?
We’ve got the answers for you. In our informative guide below, you’ll find out exactly what is meant by warm front and cold front. On top of that, we’ll highlight the difference between them, and tell you how they form.
Warm And Cold Fronts: What Are They?
To begin with, let’s look at answering the main question. Cold fronts happen on the boundary where a cold mass of air is moving into a region that is warm.
They are often linked to low pressure systems. Warm fronts, on the other hand, happen on the boundary where a mass of warm air is crossing over into a region that.
They are often linked with high pressure systems. As you can tell, warm fronts and cold fronts are the opposite of each other.
Pressure Systems
Many people are confused by the pressure systems that the fronts are linked to, mixing them up. A high pressure system is linked to warm and dry weather. On the other hand, a low pressure system is closely related to cold and wet weather.
Warm And Cold Fronts: What’s The Difference?
By now, you will be able to tell the very general differences between cold fronts and warm fronts. However, we’re going to go into more individual detail with each, allowing you to better tell the differences and similarities between them.
Both of the fronts are complicated weather systems full of complex detail, therefore they need a thorough look at.
Earlier in the article, we spoke about how each front is to do with a mass of air moving into a region that is the opposite of the air’s temperature.
For example, a warm front happens on the boundary where a warm mass of air is going into a region that is colder. On top of this explanation of the two, we can also comment on what you might see as a result of these fronts.
Signs
When a warm front happens, it takes a while to build, gradually keeping a steady stream of rain for a prolonged period of time. In contrast to this, cold fronts can be recognized by the arrival of stormy weather, as well as rain.
It’s easier to notice cold fronts, simply because it is so in your face – warm front casual rain, by contrast, you might just get used to and ignore like white noise.
These atmospheric conditions are not the only signs of a warm front or cold front, either. On top of them, they can be recognized by the arrival of air after the front. You can likely guess what type of air comes from each, but we’ll state it anyway.
With cold fronts, there is often a body of cold air that comes after the front itself, which allows it to be easily recognized. On the other hand, a hot front will see a body of warmer air come after the front, clearly defining it as definitely not a case of cold fronts.
There are even further signs that can help you recognise what type of front you have been in the presence of, and that is clouds. With cold fronts, you will often see the front be accompanied by some storm clouds.
These clouds have a noticeable vertical buildup, which makes them look like a cumulonimbus cloud, which are often very noticeably tall and sometimes taller than they are long.
In the case of a warm front, though, it will be accompanied by some uniform stratus clouds that are low lying. These are often gray and stay for a long period of time.
Defining Warm Fronts And Cold Fronts
Now that we’ve looked at how you can recognize these two different types of fronts, such as clouds and air temperature, we can go into both warm fronts and cold fronts on an individual level.
With this thorough breakdown, you will be able to better understand how they both come about in nature.
Defining Warm Fronts
As you now know, a warm front is when a mass of warm air enters into a region that has much cooler air. It’s all about contrasts. They are linked with high pressure systems, which have connotations of warm and dry weather.
A warm front will gradually build over a long period of time, which might make it not as easily noticeable. Part of the reason for that lack of clarity is because it creates gentle rain, which many of us may just ignore.
By contrast, the storms created by cold fronts, which we’ll get onto later, are harder to ignore.
Humid
We mentioned just now that a warm front is linked to a high pressure system, which is often known for dry and warm weather. However, this is not always the case with a warm front, and it is a popular misconception that they always are warm and dry.
Sometimes, the air after a warm front will be warm, but far from dry. There are times where the air will be humid, which is known for its high presence of water vapor in the atmosphere, which would make it almost the opposite of dry.
This is often a good thing, because it makes the perfect conditions for gentle and constant rain – which does wonders for when it’s over some agricultural land, as it will help the crops to flourish and grow. By contrast, a dry atmosphere would not help them.
Air Pressure
With a high pressure system, the air pressure lowers as the front comes near. Once the mass of air has gone past the area, though, the pressure begins to level again.
As the air behind it enters into the region, the air pressure begins to rise again, eventually returning it to its previous pressure state before the warm front affected it.
Occluded Fronts
An occurrence called then an “occluded front” can happen. These aren’t too much more complicated, happening when cold fronts catch up to warm fronts.
This is actually more likely to happen than you might think, because warm fronts move more slowly than cold fronts. For that reason, it is easy for the slow front to catch up and cause this occluded phenomenon.
If you want to look out for a warm front on your weather report on the TV, then they will use the symbol of a red curve with little red half-circles going across it.
It almost looks like an eyelash cartoon, with the circles facing whichever way that the front is going to be going.
Warm Fronts – How Do They Develop?
Warm fronts come about when a mass of warmer air enters into a regions that has colder air. Warm air is not as dense as cold air, meaning that it can’t displace it, which means that the edge of a warm air mass slowly rises over the boundary of the cooler air.
While it rises, the air starts to cool. Eventually, its water vapor cannot be contained in the form of a gas for any longer, which then causes condensation to take place.
Since it can’t be a gas, it becomes a liquid – rain. Since the air is rising at a gentle gradient, it causes the creation of stratus clouds. These uniform clouds are the ones that are creating the constant, long periods of rain.
As the warm front is busy passing through the region, the air pressure rises and the temperature grows warmer. These are good noticeable signs that a warm front is taking place.
Defining Cold Fronts
As we’ve said before, cold fronts occur when a large mass of cold air enters into a region that has warmer air. These fronts are linked to low pressure systems, which are known for their wet and cold weather.
Cold fronts build over a mostly short period of time, yet is much more obvious in its signs and results: it is known for its harsh weather conditions, such as storms and heavy precipitation (see also ‘What Is Precipitation: All You Need To Know‘).
Sometimes, extreme weather will occur because of them too, including things like lightning and hail.
Air Density
The air of cold fronts is much more dense than warm air is, which means that it lifts warm air up into the atmosphere and forces it to cool down and condense.
The combination of condensation and lifting warm air helps to create the thunder that comes of cold fronts, as well as the thunder and occasional lightning – all because of a difference in densities.
Air Pressure
As we said, cold fronts are linked to low pressure systems, which are known for wet weather.
As the cold front comes to the warm region, the overall air pressure begins to lower, dropping to the lowest measurement when the front edge of the front passes through the region.
After the front has gone, the air pressure begins to climb again, eventually reaching its original point.
Occluded Front
In the hot front section, we spoke about occluded fronts. Cold fronts move at a much faster rate than a warm front, sometimes even double its speed. For this reason, cold fronts will often catch up with warm fronts.
This meeting of the two causes what is called an “occluded front”.
If you want to know about an incoming cold front, you can identify it by its symbol on the visual weather forecast. If a case of cold fronts is coming, then a weather map will have a blue curve with blue triangles going up one side of it.
The triangles are pointing in the direction that the cold front will be going in. By contrast, a warm front is shown by a red line with red half-circles.
Cold Fronts – How Do They Develop?
Cold fronts begin to form when a mass of cold air enters an area that has warmer air. As the cold front is entering, it causes the air pressure of the region to lower.
When it hits the lowest point that it’s going to, it will be when the cold front passes through. When the cold front has left, the air pressure will begin to climb again and eventually rise to the point that it was at originally.
Cold air is more dense than warm air, which factors a lot into cold fronts and warm fronts meeting.
The difference in density causes cold fronts to easily displace warm air, pushing it down underneath and lifting the cold air itself up higher into the atmosphere (see also ‘Everything You Need To Know About The Thermosphere‘).
The displacement is very rapid, which causes the water vapor to condense very quickly and storm clouds to be created. The speed of it all fosters the perfect scenario for thunder, storms, and heavy rain to occur.
On top of that, hail and lightning can happen too.
The temperature of the air also lowers. It keeps cool as the mass of cold air moves behind the frontal system’s leading edge. A frontal system is another term for fronts.
Warm Fronts And Cold Fronts: A Comparison
To better show the differences that we’ve discussed so far, we have made a table.
Cold Fronts
Warm Fronts
Linked to low pressure systems.
Linked to high pressure systems.
Moves faster than warm fronts and catches up with them.
Moves more slowly than cold fronts and is caught up by them.
Moves into a region of warmer air.
Moves into a region of cooler air.
Cold air is more dense than warmer air, so it displaces it. Forces warm air into the atmosphere.
Warm air is less dense than cold air, so it cannot displace it. Therefore, the cold air displaces it. Warm air rises over the cold air.
Comes with a lowering of the temperature.
Comes with a rising of the temperature.
Sudden change in weather (see also our article on the Orographic Effect). Overbearing weather: storms, heavy rain, etc.
Hi, my name is Andrew Capper and I have been a meteorologist for almost 30 years now. My line of work specializes in the scientific principles used to explain and understand the earth’s atmosphere and how that affects everyday life.
I created this website to share my knowledge and help others stay safe during extreme weather events.
I’ll be looking at weather forecasting, clouds, tornadoes, hurricanes, and much more - so, if you’ve ever been fascinated by the weather like I have been since I was a young boy, this is the site for you. Enjoy!
