NOTES WEATHER FRONTS A weather front is a boundary that forms when air masses meet that have different temperature, pressure, and humidity

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1 NOTES WEATHER FRONTS A weather front is a boundary that forms when air masses meet that have different temperature, pressure, and humidity conditions. A weather front forms along boundaries when air masses of different temperature, pressure and humidity collide. What is a weather front? Where do weather fronts form? There are several different types of fronts: A cold front occurs when you have a pocket of air in front of a mass of cold air. Cold fronts frequently move fast and cause abrupt changes in weather. At its edge, dense cold air

2 pushes warmer air out of the way. The warm air cools as it rises. If there is enough water vapor cumulus clouds may form. After it passes, the weather is cooler and drier. The L symbol on the map representing a low pressure system What is a cold front? What happens after a cold front passes? How does a cold front form? A warm front occurs when a warm air mass slides over the top of a cold air mass. Warm fronts move slowly, so rainy weather can stick around for several days. At its edge a

3 warm air mass moves over cold air. This forms stratus clouds and the result is precipitation. (light rain or snow) After a warm front passes the weather is warmer. When does a warm front occur? How do warm fronts occur? What happens when you have a warm front moving through an area? Stationary Fronts: A warm air mass meets a cold air mass, but neither is moving. What happens when you have a stationary front? What symbols are used o

4 A cold front has triangles pointing in the direction the front is moving. A warm front has half-circles facing the direction of movement. A stationary front has triangles on one side and half circles on the other. The weather usually changes when a front passes over an area. An air mass is a large amount of air with similar air pressure, temperature, and humidity (water vapor). It gets its characteristics from the area over which it forms. There are 5 major air masses that affect the weather in North America.

5 Continental Arctic bitterly cold dry air Maritime Polar cool, wet Continental Polar cold, dry Maritime Tropical warm, moist Continental Tropical hot, dry Air masses move because of air temperature and air pressure differences. This also causes wind. Air masses can cover millions of square miles. Cloud types: cirrus

6 thin wispy clouds at high altitudes. made of ice crystals indicate pleasant weather stratus form in layers may cover large parts of the sky cumulus puffy white clouds with flat bottoms form in rising currents of warm air generally mean good weather

7 Lesson 6 Learning Target: How does temperature and pressure, affect cloud formation? What do the symbols on a weather map mean? The ingredients for cloud formation are: evaporation, warm rising air, dust particles, condensation of water and air pressure. Use maps from the New Mexican to answer question #1 parts A, B, and C. What are the conditions under which clouds form? A. On map A we think it is cloudy in the southwest, the plains, parts of the southeast, and the Midwest all the way up to parts of the northeast.

8 We know this because the symbol Z represents thunderstorms. B. There are thunderstorms predicted for all of these areas. We also know this because there is a big L symbol on the map representing a low pressure system. C. We expect cloudy weather with possible precipitation when there is a low pressure system moving through an area.

9 In lessons 4-5 we learned about the movement of air. Air movement is caused by the uneven heating of 2 surfaces. This can affect weather. Air pressure: The force that air exerts (pushes) on whatever it comes into contact with. AIR PRESSURE IS THE WEIGHT OF AIR. Air pressure is greater at lower altitudes because the air exerts more force (because there is more mass) at the surface. Air pressure decreases rapidly when rising through the atmosphere.

10 Barometers are used to detect and measure changes in air pressure. Barometric pressure is the pressure exerted by the atmosphere. Air pressure in a bottle High Low Predictions observations

11 Make sure you have answered the questions for inquiry 6.2 p. 100 Check the PDF on the website!