When a cold air mass catches up with a warm air mass, the result is often a(n) front?

When a cold FRONT catches up to a warm FRONT it is called an occluded front.
When a cold AIR MASS displaces a warmer AIR MASS it is a cold front.Occluded front

Cold occluded front

Explanation:

As the cold air mass occurs in the areas of the warm air mass the cold ams tends to throw the warm air mass upwards and the resultant is the formation of the cold front and thereby developing a high pressure in the ares. And it then leads to the formation of a extratropical cyclone and there is a difference in the temperature that occurs at the surfaces. The upwards low pressure causes the formation of a narrow showers pf thunderstorms, when the enough moisture is present in the region. A drop down of the temperature occurs in the region.