A cold front is created because of density. When air warms up, the molecules that make up the air move faster, causing them to spread out further.
This makes the air less dense than the cold air, whose molecules are closer together, making it more dense. Because of this, when the two walls of air meet, the cold air cuts underneath the warm air, forcing it upwards, making it cold on the ground.
stationary ^,^
thunder storm
it means when a front is been moved up one then it becomes a warm front if it is moved down one it means a cold front
Stationary front
The cold air mass from the cold front meets the cool air that was ahead of the warm front. The warm air rises as these air masses come together.
If you mean when a mass of cold air meets a mass of warm air, then a front is created.
One of two things are created when a cold air mass meets a warm air mass. The most common thing that is created is a cold front with the cold are rising over the warm. This can cause a line of rain and storms to break out. The other is the creation of a warm front, which is more like the warm air nudging in under the cold air. This too can create rain but it is usually less turbulent.
A warm front forms.
Snow , rain , sleet
when a cold air front meets a warm air front
A warm front forms.
cunomibious
a front
front
Stationary Front
Stationary Front
Stationary Front