1. What happens to air masses meet?
Lesson 27
What happens to air masses meet?

2. Warm and cold air masses do not mix.
When warm and cold air masses meet, they collide.

3. The masses “battle” each other
The masses “battle” each other. This meeting causes many weather changes.
The boundary between two air masses is called a front.

4. A warm front forms when a moving warm air mass pushes against a cold air mass.

5. The warm air of the front pushes upward.
cold

6. It flows over the top of the cooler air mass.

7. Many clouds form along a warm front
Many clouds form along a warm front. They may reach out for 1,600 kilometers (1,000 miles) or more.

8. At first there are only thin cirrus clouds high in the sky.
Then stratus clouds more in.

9. Slowly, the clouds become lower and lower.
The sky becomes darker and darker

10. Finally, it rains.

11. Precipitation along a warm front is even and steady
Precipitation along a warm front is even and steady. It keeps falling until the front passes.

12. It may last a few days. Then the weather becomes clearer and warmer.
A warm air mass has arrived.

13. If you watch TV, you have probably seen weather maps.

14. The symbol for a warm front is
The warm front is moving in the direction of the semi-circles. In what direction would the above warm front be moving?

15. In what direction is the warm front moving?