Inside The Cyclone: What is Low-pressure?

Before you get started…
To understand this lesson well, you need to already have a good understanding of lesson 10 (precipitation) and lesson 11 (pressure). If you were confused by those two lessons don't be frustrated. These are difficult concepts to grasp. Ask your teacher for help or go through them again, but don't give up. When you figure it out, you'll understand a part of your world that most adults don't understand.

Have you ever watched the local news and heard the weathercaster say this; "Low-pressure is moving in from the west and rain is expected to develop across our area...". Television weathercasters typically mention low-pressure systems because rain is common with them. But, what is a low-pressure weather system, and how does it cause rain?

In lesson 11 we learned how to measure atmospheric pressure. In lesson 12 we learned about high pressure and the Coriolis effect. Now we will begin to better understand downward changes in pressure and what these changes mean.