3/21/2016 Chapter 25 Vocabulary: define and give one fact: page Air Mass 2.Maritime Polar 3.Maritime Tropical 4.Continental Polar 5.Continental Tropical 6.Front 7.Cold front 8.Squall line 9.Warm front 10.Stationary front 11.Occluded front 12.Polar front 13.Wave cyclones 14.Anticyclones 15.Hurricane 16.Typhoons 17.Thunderstorm 18.Tornado 19.Waterspouts 20.Bimetal thermometer 21.Thermograph 22.Electrical thermometer 23.Wind vane 24.Radar 25.Station model 26.isobars

3/21/2016 Section 25.1 How an Air Mass Forms Air Masses Form because warm air rises at the equators and cold air sinks at the poles. There are 3 convection cells in the Northern Hemisphere and 3 in the Southern Hemisphere. The Earth’s rotation and land masses cause wind to blow in different directions. In areas with small pressure differences, the air will stay long enough to develop a uniform temp and humidity. i.e. deserts, oceans, and polar areas.

3/21/2016 Section 25.1 How an Air Mass Forms Types of Air Masses Classified by the source region; Polar is cold and labeled “P”, Tropical are warm and labeled “T”, Masses that form over land are continental and labeled “c”, Masses that form over oceans are maritime and labeled “m”. These air masses can stay over the source region for days but will move because of wind and the Earth rotation eventually.

3/21/2016 Section 25.1 How an Air Mass Forms North American Air Masses Polar Air Masses Affected by seven regions, but the air can change as it moves away from it’s source region. 3 polar masses influence North America; continental polar Canadian (cP), maritime polar Pacific (mP), maritime polar Atlantic Canadian moves southeast off the Canadian ice into The United States and can moves as far south as the Gulf.

3/21/2016 Section 25.1 How an Air Mass Forms Polar Air Masses The Pacific air mass forms in the waters near Alaska. Very moist but not extremely cold, in winter they bring snow to the Pacific Coast and in summer fog. Most moisture lost crossing the mountains and bring dry weather to the Mid U.S. The Atlantic air mass normally moves off towards Europe, but sometimes in the winter brings cold cloudy weather to New England, in the summer cool and foggy weather.

3/21/2016 Section 25.1 How an Air Mass Forms Tropical Air Masses 4 influence North America; Continental Tropical, maritime tropical gulf, maritime tropical Atlantic, and maritime tropical Pacific. cT comes from the Deserts of Northern Mexico and bring clear, dry and very hot weather. mT Atlantic and Gulf bring mild cloudy weather in winter and hot humid weather, thunderstorms and hurricanes in the summer. mT pacific rarely reach the coast, but in the winter can bring heavy rain and thunderstorms.

3/21/2016 Chapter 25 section 2 Vocabulary: define and write sentences 1.Front 2.Cold front 3.Squall line 4.Warm front 5.Stationary front 6.Occluded front 7.Polar front 8.Wave cyclones 9.Anticyclones 10.Hurricane 11.Typhoons 12.Thunderstorm 13.Tornado 14.Waterspouts

Essential Question Compare the characteristic weather patterns of cold fronts and those of warm fronts Describe how a wave cyclone forms Describe the stages in the development of hurricanes, thunderstorms and tornados 3/21/2016

Section 25.2 Compare the characteristic weather patterns of cold fronts and those of warm fronts Fronts Types of Fronts A boundary between air masses Cold Front – Cold air overtakes warm air and lifts the warm air – a squall line forms on this front Warm Front – Warm air overtakes cold and rises in a gradual slope Stationary Front – is when the air masses are not displaced Occluded Front – is when a cold front push the warm air completely off the ground

3/21/2016 Section 25.2 Compare the characteristic weather patterns of cold fronts and those of warm fronts Polar Fronts Wave Cyclones A Polar front circles the earth at 40 to 60 degrees latitude in both hemispheres. In winter it is in the Middle of North America. In Summer it is North of the Great lakes The boundary along a polar front is where wave cycles form. They can grow to 2,500 km in diameter, with winds that blow in an upward circle path around the low pressure center. They have major influences on our weather.

3/21/2016 Section 25.2 Describe how a wave cyclone forms Stages of a Wave Cyclones Anticyclones Stage one there is a stationary front, the winds move parallel to the front in opposite directions. Stage two an intensifying low pressure region develops along the front, bringing stormy weather. Stage three last about 24 hours and continues to move east in North America. The process can restart. The anticyclone spins clockwise and brings dry warm air to a region or fair weather. The air is sinking

3/21/2016 Section 25.2 Describe the stages in the development of hurricanes, thunderstorms and tornadoes Hurricanes Has winds over 120 km/hr No more then 700 km in diameter A storm starts with warm moist air evaporating from the ocean rapidly The release of latent heat increases the rise of air Winds increase towards the eye The eye is clear and calm The danger is due to raising sea levels and large waves.

3/21/2016 Section 25.2 Describe the stages in the development of hurricanes, thunderstorms and tornadoes Thunderstorms Lightning, thunder and strong winds accompany this type of storm. High surface temperatures cause the rapid rise of warm moist air. In stage one a Cumulus clouds form or Cumulonimbus. Stage two is called the mature stage and is when the storm becomes dark cumulonimbus cloud with heavy torrential rains The final stage or dissipating is when the storm has used the available water vapor and the winds end.

3/21/2016 Section 25.2 Describe the stages in the development of hurricanes, thunderstorms and tornadoes Tornadoes Are the smallest, most violent and shortest lived severe storms. Starts when a thunderstorm meets high altitude horizontal winds. This may form a narrow, funnel shaped, rapidly spinning extension that may move downward to the ground. Not more than 100 m wide, path is destroyed. Winds can reach 400 km/hr Most common in an area called tornado alley in the United States. When they form over water they are called waterspouts and usually weaker.

3/21/2016 Chapter 25 section 3: Essential Question Describe the types of instruments used to measure the weather

3/21/2016 Section 25.3 Weather Instruments Measuring Air Temperature Barometers, psychrometers, rain gauges, thermometer, anemometer, radiosonde and radar Celsius and Fahrenheit used in the United States. 3 types of thermometers –Liquid use Mercury or Alchol to determine the temperature –Bimetal that expand or contract to temperature, a thermograph measures the temperature change –Electrical use the flow of electric current through certain materials

3/21/2016 Section 25.3 Measuring Wind Speed and Direction Measuring upper- atmospheric conditions An anemometer measures in m/sec, MPH, or knots. A wind vane tells you the direction the wind comes from. The points into the wind. A radiosonde is attached to a helium filled balloon to measure weather conditions in the upper atmosphere Radar can also be used to detect water droplets, Doppler can even give direction Satellites can also be used to measure cloud. Land and sea temperatures.

3/21/2016 Chapter 25 section 4 Essential question Explain how a weather map is made

3/21/2016 Section 25.4 Forecasting the weather History – more then 4,000 years of trying to predict the weather The invention of the thermometer and barometer made forecasting possible In 1844 the telegraph made it so data could be shared quickly 1870 the U.S. formed the Weather forecasting agency, renamed the National Weather Service Data is collected from around the world every 6 hours

3/21/2016 Section 25.4 Cornell Notes Making a Weather Map Map

3/21/2016 Section 25.4

3/21/2016 Section 25.4 Types of forecasting Controlling the weather Two types daily and long term Daily – weather for the next 24 hours – local daily can be as much as 5 days Long range forecast covers monthly & seasonal outlooks Cloud seeding has been used to reduce the intensity of storms with limited results. Some experimentation still continues.