Sec 13.4 - Highland High School
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Section 13.4 Recurrent Weather Objectives Describe recurring weather patterns and the problems they create. Identify atmospheric events that cause recurring weather patterns. Distinguish between heat waves and cold waves. Section 13.4 Recurrent Weather Even a relatively mild weather system can become destructive and dangerous if it persists for long periods of time. Review Vocabulary Fahrenheit scale: a temperature scale in which water freezes at 32 and boils at 212 Section 13.4 Recurrent Weather New Vocabulary drought cold wave heat wave wind-chill index Section 13.4 Recurrent Weather Floods The most extensive flooding occurs as a result of heavy and persistent rain, saturated soil, and low-lying ground. Floods can also occur when weather patterns cause even mild storms to persist over the same area. Section 13.4 Recurrent Weather Floods Low-lying areas are most susceptible to flooding, making coastlines particularly vulnerable to storm surges during hurricanes. Rivers in narrow-walled valleys and streambeds can rise rapidly, creating highpowered and destructive walls of water. Section 13.4 Recurrent Weather Droughts Droughts are extended periods of wellbelow-average rainfall. Droughts are usually the result of highpressure systems that persist for weeks or months over continental areas. Section 13.4 Recurrent Weather Droughts Because the sinking air prevents humid air from rising, condensation cannot occur, and drought sets in until global patterns shift enough to move the high-pressure system. Section 13.4 Recurrent Weather Droughts Heat waves An unpleasant side effect of droughts often comes in the form of heat waves, which are extended periods of above-average temperatures. Heat waves can be formed by the same high-pressure systems that cause droughts. Section 13.4 Recurrent Weather Droughts Heat waves Because of the dangers posed by a combination of heat and humidity, the National Weather Service (NWS) routinely reports the heat index. The heat index assesses the effect of the body’s difficulty in regulating its internal temperature as relative humidity rises. Section 13.4 Recurrent Weather Please click the image above to view the interactive table. Section 13.4 Recurrent Weather Cold Waves The opposite of a heat wave is a cold wave, which is an extended period of belowaverage temperatures. Cold waves are also brought on by large, high-pressure systems. However, cold waves are caused by systems of continental polar or arctic origin. Section 13.4 Recurrent Weather Cold Waves Because of the location and the time of year in which they occur, winter highpressure systems are much more influenced by the jet stream than are summer high-pressure systems. Section 13.4 Recurrent Weather Cold Waves The winter location of the jet stream can remain essentially unchanged for days or even weeks. This means that several polar high-pressure systems can follow the same path and subject the same areas to continuous numbing cold. Section 13.4 Recurrent Weather Cold Waves Wind-chill index The effects of cold air on the human body are magnified by wind. Known as the wind-chill factor, this phenomenon is measured by the wind-chill index. Section 13.4 Recurrent Weather Cold Waves Wind-chill index The wind-chill chart was designed to show the dangers of cold and wind. CH Study Guide Key Concepts Section 13.4 Recurrent Weather Even a relatively mild weather system can become destructive and dangerous if it persists for long periods of time. Too much heat and too little precipitation causes droughts. Too little heat and a stalled jet stream can cause weeks of cold weather in an area. CH Study Guide Key Concepts Section 13.4 Recurrent Weather Heat index estimates the effect on the human body when the air is hot and the humidity is high. Cold index tells how wind, humidity, and temperature affect your body in winter. Wind chill is a factor used to warn about the effect of cold air and wind on the human body. CH The Nature of Storms 13.4 Section Questions The temperature is 0F and the wind speed is 30 miles per hour. What is the wind chill? a. –5F b. –10F c. –26F d. –58F CH The Nature of Storms 13.4 Section Questions What happens to air at the center of a high-pressure system? a. It sinks and water vapor condenses. b. It sinks and water vapor resists condensation. c. It rises and water vapor condenses. d. It rises and water vapor resists condensation. CH The Nature of Storms 13.4 Section Questions What conditions result in extensive flooding? Possible answer: The most extensive flooding occurs as a result of heavy and persistent rain, saturated soil, and lowlying ground. CH The Nature of Storms Chapter Assessment Questions Which weather event is often related to the presence of persistent high pressure over a region? a. a flood b. a drought c. a tornado d. a blizzard CH The Nature of Storms Chapter Assessment Questions Which type of movement describes the air flow in the eyewall of a hurricane? a. counterclockwise upward spiral b. clockwise upward spiral c. counterclockwise downward spiral d. clockwise downward spiral CH The Nature of Storms Chapter Assessment Questions Why do people feel less comfortable on a hot day when the humidity is high? a. The air is less dense. b. The air moves less. c. Less evaporation occurs. d. Less precipitation occurs. CH The Nature of Storms Chapter Assessment Questions Which type of thunderstorm could form as a result of the air circulation shown? a. mountain thunderstorm b. sea-breeze thunderstorm c. cold-front thunderstorm d. warm-front thunderstorm CH The Nature of Storms Chapter Assessment Questions What hazards do hurricanes cause when they make landfall? Possible answer: Hurricanes making landfall bring high wind, tornadoes, and sometimes severe lightning. Storm surge causes flooding along the coast, and heavy rain causes flooding inland. CH The Nature of Storms Standardized Test Practice What forms as superheated air expands and produces a shock wave? a. lightning b. thunder c. tornado d. microburst CH The Nature of Storms Standardized Test Practice What is the Saffir-Simpson scale? a. a scale for classifying tornadoes b. a scale for classifying hurricanes c. a scale for classifying thunderstorms d. a scale for classifying lightning CH The Nature of Storms Standardized Test Practice On which side of a northern hemisphere tropical cyclone does the wind blow from the south? a. north side b. west side c. south side d. east side CH The Nature of Storms Standardized Test Practice How is the life cycle of a supercell thunderstorm similar to the life cycle of a hurricane? Possible answer: Both storms form from energy supplied by rising moist air, and both storms dissipate when the supply of rising moist air is cut off. CH The Nature of Storms Standardized Test Practice Why do hailstones consist of concentric layers? CH The Nature of Storms Standardized Test Practice Possible answer: The layers form as hailstones are tossed in a thunderstorm by strong updrafts. A new layer of ice is added each time the hailstone moves into a level of supercooled water droplets. These water droplets exist at temperatures that are well below the normal freezing point of water and so change to ice as soon as they come into contact with the hailstone.
