Warmup 4/13/16 Why do you think it’s important to learn about weather? Objective Tonight’s Homework To learn specifics of what happens when masses of air move Prepare short presentation on weather for Friday

Weather and Humanity Last unit we talked about winds and precipitation. How air moves and what happens when it warms or cools. But with this unit, we want to get a bit more detailed. Why exactly do clouds form when they do? What happens when a bunch of cold dry air hits a bunch of hot wet air? How do things like tornadoes form? What about hurricanes? What’s the best way to keep safe?

Weather and Humanity Most weather is caused by warm and cold fronts. These are areas where large blobs of warm and cold air come into contact with one another. The kind of weather we get mainly depends on two things: the temperature of the blob and the humidity of the blob.

Weather and Humanity If we have a warm blob move into a cold one, we get a warm front. When the warm air hits the cold, the warm air goes up over the cold air (always). As it rises up, it cools and condenses. This usually produces rain and snow. Since the wedge is thin, these clouds form over a pretty wide area.

Weather and Humanity Signs that a warm front is moving in: - Cold temperatures suddenly increase - Pressure drops then holds steady - Winds shift from heading SE to heading SW - Dew point rises then stays steady

Weather and Humanity If we have a cold blob move into a warm one, we get a cold front. Just like with the warm front, this pushes warm air up and turns it into storm clouds. However, this makes tall cumulonimbus clouds rather than spread out different types.

Weather and Humanity We can also have a third kind of front called an occluded front. In this type, we have a blob of warm air between a blob of cool air and a blob of cold air. As the cold blob moves in, it pushes the warm one up completely off the ground. This causes tons of rain and storms.

Weather and Humanity Our last kind of front is a stationary front. This is where our warm and cold blobs are moving sideways past each other rather than the warm one getting pushed over the cold one. These usually create a few storms as some of the warm air will mix and get pushed up on top of the cold air. In general, though, any time we have a front, there will be storms all along the length of it.

Weather and Humanity There are a few other things that can cause storms, though. On a hot day, the ground warms up. This heats up the air above it, which starts to rise. As this air rises, it can form clouds, which then turn into storms. We actually get this a lot here in Colorado during the summer. It’s most evident on afternoons where we get about 15 minutes of sudden rainfall that stop just as quickly as they start.

Weather and Humanity Mountains can also create clouds. As warm air hits a mountain range, the air rises and cools. As it cools, it forms clouds and rain. The air that makes it over the mountains is now very dry and creates what we call a rain shadow. We call this whole process orthographic lifting.

Severe Weather Section 20B covers severe weather. Rather than doing a ton of notes, Mr. C. is going to have you guys do some research and make a construction-paper poster that will be due Friday. Here’s what you need to do: Pick one of the following kinds of disasters: - Blizzard - Ice storm - Thunderstorm - Tornado - Hurricane Create a poster that gives the following information: - What causes this disaster in terms of weather and air? - What was the worst one that ever happened? Describe - What is the biggest hazard or danger from this disaster? - How can you keep safe during this kind of disaster?

Exit Question A warm front is caused when… A blob of cold air suddenly heats up and rises A blob of hot air suddenly cools and drops A blob of warm air moves into an area with cold air A blob of cold air moves into an area with warm air All of the above None of the above