2High and Low Pressure Areas High pressure causes air to sinkUsually results in several days of clear sunny skiesAir rises in low pressure areas and forms water dropletsUsually results in rain and storms
3Barometer – tool used to measure air pressure. High pressure brings mild winds, stable temperatures, and clear weather.Low pressure brings strong winds, dropping temperatures and precipitation.HL
4L H Barometric Pressure – tells us when weather will change. when it falls - low pressure moving inwhen it rises- high pressure moving inWarm air= expanding or rising air= leaves behind L pressureAir PressureLAir PressureCold Air=sinking air= leaves an area of H pressureH
8The Jet Stream guides the movement of different air masse s across the United States.A jet stream forms high in the upper troposphere over the boundary between two air masses of different temperature.The greater the temperature difference between the air masses, the greater the air pressure difference, and the faster the wind blows in the jet stream.This river of air has wind speeds which often exceed 100 mph, and sometimes peak over 200 mph.Jet streams usually form in the winter, when there is a greater contrast in temperature between cold continental air masses and warm oceanic air masses.8
9Wind is caused by air flowing from high pressure to low pressure Wind is caused by air flowing from high pressure to low pressure. Since the Earth is rotating, however, the air does not flow directly from high to low pressure, but it is deflected to the right (in the Northern Hemisphere; to the left in the Southern Hemisphere), so that the wind flows around the high and low pressure areas.The closer the high and low pressure areas are together, the stronger the "pressure gradient", and the stronger the winds. On weather maps, lines of constant pressure are drawn (as in the example, above) which are called "isobars". The closer these lines are together, the stronger the wind.9
11Air masses are like the surface they form over. a huge “bubble” of air that shares the same temperature and pressure (can be big enough to cover several states!)Air Masses are huge clumps of air that move around the Earth, bringing changes in…weather.Air masses are like the surface they form over.
12The air mass shown above formed over land in northern Canada. Therefore the air mass will be…cold and dry.
13H A polar air mass brings cold air Cold Air Mass – this is an air mass made up of cool temperatures and high pressure.Usually does not hold much moistureForms over cold water or land.H
14The pink air mass formed over the ocean near the equator. The air mass will be…warm and moist.
15Warm Air Mass – this is an air mass made up of warm air that has a low pressure. Usually holds a lot of moisture.Forms over hot land or water.LA tropical air mass brings warm air
18Thunderstorms pushes the warm air up quickly. During a cold front, a cold air mass catches up to a warm air mass and…pushes the warm air up quickly.Weather associated with cold fronts is…Thunderstorms
23The map symbol for a warm front is a curved line with small… rounded knobsWhen warm air catches up to a cold air mass, what is formed?...warm front
24slides over the top of the cold air, When a warm air mass catches up with a cold air mass, it forms a…warm frontThe warm air…slides over the top of the cold air,before …pushing it away.Weather associated with warm fronts are….Clouds and long periods of steady rain
25From the map above, you can predict that the weather over the Great Lakes will be getting … warmer
26Warm or cold front stops moving. Light wind and precipitation may occur across the front boundary