What happens when a cold front catches up to a warm front?

Question

What happens when a cold front catches up to a warm front?

Answer 1

You get what is called an occlusion, and thus an occluded front.  This is not uncommon in low pressure systems that are some days old.  There can be various types of weather associated with occluded fronts, but typically not a extreme as along co0ld or warm fronts.  

Answer 2

a storm