Because cold fronts move faster than warm fronts, they will catch up and overtake the warm front. This becomes an occluded front, which is show by the purple line and symbols and indicates that a storm is weakening. Instead of a boundary for two air masses, an occluded front is a boundary for three; a cold, a cool, and a warm air mass. Typically, the precipitation associated with an occluded front is like a cold front, and the temperatures will vary; depending on the air masses.