0
Visit Your Local PBS Station PBS Home PBS Home Programs A-Z TV Schedules Watch Video Donate Shop PBS Search PBS
0
Rough Science
Explore the Challenges
Solve the Web Challenge
Meet the Rough Scientists
About the TV Series
Discover More
Feedback
Site Map
Explore the Challenges

The Challenge: Predict the Weather



What happens at the boundaries between warm and cold masses of air?

When warmer air replaces cooler air, it is called a warm front. Similarly, a cold front describes the situation when a mass of cooler air replaces warm air. These fronts are shown on weather charts as lines with either red semi-circles (indicating a warm front) or blue triangles (showing a cold front). These symbols are placed on one side of the frontal line to show which way the front is moving.

Warm front Cold front

As cold fronts move more quickly than warm fronts, they can catch up with the warm front ahead. This is called an occlusion.

Occlusion
Occlusion